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Tu R, Ping Z, Liu J, Tsoi ML, Song X, Liu W, Xie T. Niche Tet maintains germline stem cells independently of dioxygenase activity. EMBO J 2024; 43:1570-1590. [PMID: 38499787 PMCID: PMC11021519 DOI: 10.1038/s44318-024-00074-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 02/19/2024] [Accepted: 02/23/2024] [Indexed: 03/20/2024] Open
Abstract
Ten-eleven translocation (TET) proteins are dioxygenases that convert 5-methylcytosine (5mC) into 5-hydroxylmethylcytosine (5hmC) in DNA and RNA. However, their involvement in adult stem cell regulation remains unclear. Here, we identify a novel enzymatic activity-independent function of Tet in the Drosophila germline stem cell (GSC) niche. Tet activates the expression of Dpp, the fly homologue of BMP, in the ovary stem cell niche, thereby controlling GSC self-renewal. Depletion of Tet disrupts Dpp production, leading to premature GSC loss. Strikingly, both wild-type and enzyme-dead mutant Tet proteins rescue defective BMP signaling and GSC loss when expressed in the niche. Mechanistically, Tet interacts directly with Bap55 and Stat92E, facilitating recruitment of the Polybromo Brahma associated protein (PBAP) complex to the dpp enhancer and activating Dpp expression. Furthermore, human TET3 can effectively substitute for Drosophila Tet in the niche to support BMP signaling and GSC self-renewal. Our findings highlight a conserved novel catalytic activity-independent role of Tet as a scaffold protein in supporting niche signaling for adult stem cell self-renewal.
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Affiliation(s)
- Renjun Tu
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Special Administrative Region, China
| | - Zhaohua Ping
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO, USA
| | - Jian Liu
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Centre, Shenzhen, Guangdong, China
| | - Man Lung Tsoi
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Special Administrative Region, China
- Centre for Regenerative Medicine and Health, Hong Kong Institute of Science and Innovation, Chinese Academy of Sciences, New Territories, Hong Kong Special Administrative Region, China
| | - Xiaoqing Song
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO, USA
| | - Wei Liu
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Centre, Shenzhen, Guangdong, China
| | - Ting Xie
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Special Administrative Region, China.
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO, USA.
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2
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Chen J, Li C, Sheng Y, Zhang J, Pang L, Dong Z, Wu Z, Lu Y, Liu Z, Zhang Q, Guan X, Chen X, Huang J. Communication between the stem cell niche and an adjacent differentiation niche through miRNA and EGFR signaling orchestrates exit from the stem cell state in the Drosophila ovary. PLoS Biol 2024; 22:e3002515. [PMID: 38512963 PMCID: PMC10986965 DOI: 10.1371/journal.pbio.3002515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 04/02/2024] [Accepted: 01/22/2024] [Indexed: 03/23/2024] Open
Abstract
The signaling environment, or niche, often governs the initial difference in behavior of an adult stem cell and a derivative that initiates a path towards differentiation. The transition between an instructive stem cell niche and differentiation niche must generally have single-cell resolution, suggesting that multiple mechanisms might be necessary to sharpen the transition. Here, we examined the Drosophila ovary and found that Cap cells, which are key constituents of the germline stem cell (GSC) niche, express a conserved microRNA (miR-124). Surprisingly, loss of miR-124 activity in Cap cells leads to a defect in differentiation of GSC derivatives. We present evidence that the direct functional target of miR-124 in Cap cells is the epidermal growth factor receptor (EGFR) and that failure to limit EGFR expression leads to the ectopic expression of a key anti-differentiation BMP signal in neighboring somatic escort cells (ECs), which constitute a differentiation niche. We further found that Notch signaling connects EFGR activity in Cap cells to BMP expression in ECs. We deduce that the stem cell niche communicates with the differentiation niche through a mechanism that begins with the selective expression of a specific microRNA and culminates in the suppression of the major anti-differentiation signal in neighboring cells, with the functionally important overall role of sharpening the spatial distinction between self-renewal and differentiation environments.
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Affiliation(s)
- Jiani Chen
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
- Zhejiang Provincial Key Laboratory of Crop Genetic Resources, Institute of Crop Science, Plant Precision Breeding Academy, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China
| | - Chaosqun Li
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Yifeng Sheng
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Junwei Zhang
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Lan Pang
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
- Zhejiang Provincial Key Laboratory of Crop Genetic Resources, Institute of Crop Science, Plant Precision Breeding Academy, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China
| | - Zhi Dong
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Zhiwei Wu
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Yueqi Lu
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Zhiguo Liu
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Qichao Zhang
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
- Zhejiang Provincial Key Laboratory of Crop Genetic Resources, Institute of Crop Science, Plant Precision Breeding Academy, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China
| | - Xueying Guan
- Zhejiang Provincial Key Laboratory of Crop Genetic Resources, Institute of Crop Science, Plant Precision Breeding Academy, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China
- Hainan Institute of Zhejiang University, Yazhou Bay Science and Technology City, Sanya, China
| | - Xuexin Chen
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
- Hainan Institute of Zhejiang University, Yazhou Bay Science and Technology City, Sanya, China
| | - Jianhua Huang
- Institute of Insect Sciences, Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang University, Hangzhou, China
- Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou, China
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3
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Sun Z, Nystul TG, Zhong G. Single-cell RNA sequencing identifies eggplant as a regulator of germ cell development in Drosophila. EMBO Rep 2023; 24:e56475. [PMID: 37603128 PMCID: PMC10561367 DOI: 10.15252/embr.202256475] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 07/27/2023] [Accepted: 08/01/2023] [Indexed: 08/22/2023] Open
Abstract
Drosophila ovarian germline stem cells (GSCs) are a powerful model for stem cell research. In this study, we use single-cell RNA sequencing (scRNA-seq), an RNAi screen and bioinformatic analysis, to identify genes involved in germ cell differentiation, including 34 genes with upregulated expression during early germ cell development and 19 genes that may regulate germ cell differentiation. Among these, a gene we have named eggplant (eggpl) is highly expressed in GSCs and downregulated in early daughter cells. RNAi knockdown of eggpl causes germ cell proliferation and differentiation defects. In flies fed a rich yeast diet, the expression of eggpl is significantly lower and knockdown or knockout of eggpl phenocopies a rich diet. In addition, eggpl knockdown suppresses the reduction in germ cell proliferation caused by inhibition of the insulin effector PI3K. These findings suggest that downregulation of eggpl links nutritional status to germ cell proliferation and differentiation. Collectively, this study provides new insights into the signaling networks that regulate early germ cell development and identifies eggpl as a key player in this process.
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Affiliation(s)
- Zhipeng Sun
- Key Laboratory of Crop Integrated Pest Management in South China, Ministry of Agriculture and Rural AffairsSouth China Agricultural UniversityGuangzhouChina
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of EducationSouth China Agricultural UniversityGuangzhouChina
| | | | - Guohua Zhong
- Key Laboratory of Crop Integrated Pest Management in South China, Ministry of Agriculture and Rural AffairsSouth China Agricultural UniversityGuangzhouChina
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of EducationSouth China Agricultural UniversityGuangzhouChina
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4
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Tu R, Tang XA, Xu R, Ping Z, Yu Z, Xie T. Gap junction-transported cAMP from the niche controls stem cell progeny differentiation. Proc Natl Acad Sci U S A 2023; 120:e2304168120. [PMID: 37603749 PMCID: PMC10468610 DOI: 10.1073/pnas.2304168120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 07/22/2023] [Indexed: 08/23/2023] Open
Abstract
The niche has been shown to control stem cell self-renewal in different tissue types and organisms. Recently, a separate niche has been proposed to control stem cell progeny differentiation, called the differentiation niche. However, it remains poorly understood whether and how the differentiation niche directly signals to stem cell progeny to control their differentiation. In the Drosophila ovary, inner germarial sheath (IGS) cells contribute to two separate niche compartments for controlling both germline stem cell (GSC) self-renewal and progeny differentiation. In this study, we show that IGS cells express Inx2 protein, which forms gap junctions (GJs) with germline-specific Zpg protein to control stepwise GSC lineage development, including GSC self-renewal, germline cyst formation, meiotic double-strand DNA break formation, and oocyte specification. Germline-specific Zpg and IGS-specific Inx2 knockdowns cause similar defects in stepwise GSC development. Additionally, secondary messenger cAMP is transported from IGS cells to GSCs and their progeny via GJs to activate PKA signaling for controlling stepwise GSC development. Therefore, this study demonstrates that the niche directly controls GSC progeny differentiation via the GJ-cAMP-PKA signaling axis, which provides important insights into niche control of stem cell differentiation and highlights the importance of GJ-transported cAMP in tissue regeneration. This may represent a general strategy for the niche to control adult stem cell development in various tissue types and organisms since GJs and cAMP are widely distributed.
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Affiliation(s)
- Renjun Tu
- Division of Life Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong Special Administrative Region (SAR), China
| | - Xiaohan Alex Tang
- Division of Life Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong Special Administrative Region (SAR), China
| | - Rui Xu
- Division of Life Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong Special Administrative Region (SAR), China
| | - Zhaohua Ping
- Stowers Institute for Medical Research, Kansas City, MO64110
| | - Zulin Yu
- Stowers Institute for Medical Research, Kansas City, MO64110
| | - Ting Xie
- Division of Life Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong Special Administrative Region (SAR), China
- Stowers Institute for Medical Research, Kansas City, MO64110
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5
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Abstract
BACKGROUND Maintenance of the Drosophila male germline stem cells (GSCs) requires activation of the Janus kinase/signal transducer and activators of transcription (JAK/STAT) pathway by niche signals. The precise role of JAK/STAT signaling in GSC maintenance, however, remains incompletely understood. RESULTS Here, we show that, GSC maintenance requires both canonical and non-canonical JAK/STAT signaling, in which unphosphorylated STAT (uSTAT) maintains heterochromatin stability by binding to heterochromatin protein 1 (HP1). We found that GSC-specific overexpressing STAT, or even the transcriptionally inactive mutant STAT, increases GSC number and partially rescues the GSC-loss mutant phenotype due to reduced JAK activity. Furthermore, we found that both HP1 and STAT are transcriptional targets of the canonical JAK/STAT pathway in GSCs, and that GSCs exhibit higher heterochromatin content. CONCLUSIONS These results suggest that persistent JAK/STAT activation by niche signals leads to the accumulation of HP1 and uSTAT in GSCs, which promote heterochromatin formation important for maintaining GSC identity. Thus, the maintenance of Drosophila GSCs requires both canonical and non-canonical STAT functions within GSCs for heterochromatin regulation.
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Affiliation(s)
- Yalan Xing
- Department of Medicine, University of California at San Diego, La Jolla, California, USA.,Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, New York, USA
| | - Kimberly Larson
- Department of Medicine, University of California at San Diego, La Jolla, California, USA.,Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, New York, USA
| | - Jinghong Li
- Department of Medicine, University of California at San Diego, La Jolla, California, USA
| | - Willis X Li
- Department of Medicine, University of California at San Diego, La Jolla, California, USA.,Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, New York, USA
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6
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Szarka-Kovács AB, Takács Z, Bence M, Erdélyi M, Jankovics F. Drosophila MESR4 Gene Ensures Germline Stem Cell Differentiation by Promoting the Transcription of bag of marbles. Cells 2022; 11:cells11132056. [PMID: 35805140 PMCID: PMC9265997 DOI: 10.3390/cells11132056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 06/22/2022] [Accepted: 06/24/2022] [Indexed: 12/02/2022] Open
Abstract
Ovarian germline stem cells (GSCs) of Drosophila melanogaster provide a valuable in vivo model to investigate how the adult stem cell identity is maintained and the differentiation of the daughter cells is regulated. GSCs are embedded into a specialized cellular microenvironment, the so-called stem cell niche. Besides the complex signaling interactions between the germ cells and the niche cells, the germ cell intrinsic mechanisms, such as chromatin regulation and transcriptional control, are also crucial in the decision about self-renewal and differentiation. The key differentiation regulator gene is the bag of marbles (bam), which is transcriptionally repressed in the GSCs and de-repressed in the differentiating daughter cell. Here, we show that the transcription factor MESR4 functions in the germline to promote GSC daughter differentiation. We find that the loss of MESR4 results in the accumulation of GSC daughter cells which fail to transit from the pre-cystoblast (pre-CB) to the differentiated cystoblast (CB) stage. The forced expression of bam can rescue this differentiation defect. By a series of epistasis experiments and a transcriptional analysis, we demonstrate that MESR4 positively regulates the transcription of bam. Our results suggest that lack of repression alone is not sufficient, but MESR4-mediated transcriptional activation is also required for bam expression.
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Affiliation(s)
- Alexandra Brigitta Szarka-Kovács
- Institute of Genetics, Biological Research Centre, Eötvös Loránd Research Network, H-6726 Szeged, Hungary; (A.B.S.-K.); (Z.T.); (M.B.)
- Doctoral School in Biology, University of Szeged, H-6720 Szeged, Hungary
| | - Zsanett Takács
- Institute of Genetics, Biological Research Centre, Eötvös Loránd Research Network, H-6726 Szeged, Hungary; (A.B.S.-K.); (Z.T.); (M.B.)
| | - Melinda Bence
- Institute of Genetics, Biological Research Centre, Eötvös Loránd Research Network, H-6726 Szeged, Hungary; (A.B.S.-K.); (Z.T.); (M.B.)
| | - Miklós Erdélyi
- Institute of Genetics, Biological Research Centre, Eötvös Loránd Research Network, H-6726 Szeged, Hungary; (A.B.S.-K.); (Z.T.); (M.B.)
- Correspondence: (M.E.); (F.J.)
| | - Ferenc Jankovics
- Institute of Genetics, Biological Research Centre, Eötvös Loránd Research Network, H-6726 Szeged, Hungary; (A.B.S.-K.); (Z.T.); (M.B.)
- Department of Medical Biology, Albert Szent-Györgyi Medical School, University of Szeged, H-6720 Szeged, Hungary
- Correspondence: (M.E.); (F.J.)
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7
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Hayashi Y, Kashio S, Murotomi K, Hino S, Kang W, Miyado K, Nakao M, Miura M, Kobayashi S, Namihira M. Biosynthesis of S-adenosyl-methionine enhances aging-related defects in Drosophila oogenesis. Sci Rep 2022; 12:5593. [PMID: 35379840 PMCID: PMC8979982 DOI: 10.1038/s41598-022-09424-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 03/23/2022] [Indexed: 11/09/2022] Open
Abstract
AbstractTissue aging is a major cause of aging-related disabilities and a shortened life span. Understanding how tissue aging progresses and identifying the factors underlying tissue aging are crucial; however, the mechanism of tissue aging is not fully understood. Here we show that the biosynthesis of S-adenosyl-methionine (SAM), the major cellular donor of methyl group for methylation modifications, potently accelerates the aging-related defects during Drosophila oogenesis. An aging-related increase in the SAM-synthetase (Sam-S) levels in the germline leads to an increase in ovarian SAM levels. Sam-S-dependent biosynthesis of SAM controls aging-related defects in oogenesis through two mechanisms, decreasing the ability to maintain germline stem cells and accelerating the improper formation of egg chambers. Aging-related increases in SAM commonly occur in mouse reproductive tissue and the brain. Therefore, our results raise the possibility suggesting that SAM is the factor related to tissue aging beyond the species and tissues.
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Shore T, Levi T, Kalifa R, Dreifuss A, Rekler D, Weinberg-Shukron A, Nevo Y, Bialistoky T, Moyal V, Gold MY, Leebhoff S, Zangen D, Deshpande G, Gerlitz O. Nucleoporin107 mediates female sexual differentiation via Dsx. eLife 2022; 11:72632. [PMID: 35311642 PMCID: PMC8975549 DOI: 10.7554/elife.72632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 03/17/2022] [Indexed: 11/13/2022] Open
Abstract
We recently identified a missense mutation in Nucleoporin107 (Nup107; D447N) underlying XX-ovarian-dysgenesis, a rare disorder characterized by underdeveloped and dysfunctional ovaries. Modeling of the human mutation in Drosophila or specific knockdown of Nup107 in the gonadal soma resulted in ovarian-dysgenesis-like phenotypes. Transcriptomic analysis identified the somatic sex-determination gene doublesex (dsx) as a target of Nup107. Establishing Dsx as a primary relevant target of Nup107, either loss or gain of Dsx in the gonadal soma is sufficient to mimic or rescue the phenotypes induced by Nup107 loss. Importantly, the aberrant phenotypes induced by compromising either Nup107 or dsx are reminiscent of BMP signaling hyperactivation. Remarkably, in this context, the metalloprotease AdamTS-A, a transcriptional target of both Dsx and Nup107, is necessary for the calibration of BMP signaling. As modulation of BMP signaling is a conserved critical determinant of soma-germline interaction, the sex and tissue specific deployment of Dsx-F by Nup107 seems crucial for the maintenance of the homeostatic balance between the germ cells and somatic gonadal cells.
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Affiliation(s)
- Tikva Shore
- Department of Developmental Biology and Cancer Research, The Hebrew University, Jerusalem, Israel
| | - Tgst Levi
- Department of Developmental Biology and Cancer Research, The Hebrew University, Jerusalem, Israel
| | - Rachel Kalifa
- Department of Developmental Biology and Cancer Research, The Hebrew University, Jerusalem, Israel
| | - Amatzia Dreifuss
- Department of Developmental Biology and Cancer Research, The Hebrew University, Jerusalem, Israel
| | - Dina Rekler
- Department of Developmental Biology and Cancer Research, The Hebrew University, Jerusalem, Israel
| | | | - Yuval Nevo
- Bioinformatics Unit of the I-CORE Computation Center, The Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Tzofia Bialistoky
- Department of Developmental Biology and Cancer Research, The Hebrew University, Jerusalem, Israel
| | - Victoria Moyal
- Department of Developmental Biology and Cancer Research, The Hebrew University, Jerusalem, Israel
| | - Merav Yaffa Gold
- Department of Developmental Biology and Cancer Research, The Hebrew University, Jerusalem, Israel
| | - Shira Leebhoff
- Department of Developmental Biology and Cancer Research, The Hebrew University, Jerusalem, Israel
| | - David Zangen
- Division of Pediatric Endocrinology, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Girish Deshpande
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Offer Gerlitz
- Department of Developmental Biology and Cancer Research, The Hebrew University, Jerusalem, Israel
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Dunipace L, Newcomb S, Stathopoulos A. brinker levels regulated by a promoter proximal element support germ cell homeostasis. Development 2022; 149:274023. [PMID: 35037688 PMCID: PMC8918798 DOI: 10.1242/dev.199890] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 12/22/2021] [Indexed: 12/24/2022]
Abstract
ABSTRACT
A limited BMP signaling range in the stem cell niche of the ovary protects against germ cell tumors and promotes germ cell homeostasis. The canonical repressor of BMP signaling in both the Drosophila embryo and wing disc is the transcription factor Brinker (Brk), yet the expression and potential role of Brk in the germarium has not previously been described. Here, we find that brk expression requires a promoter-proximal element (PPE) to support long-distance enhancer action as well as to drive expression in the germarium. Furthermore, PPE subdomains have different activities; in particular, the proximal portion acts as a damper to regulate brk levels precisely. Using PPE mutants as well as tissue-specific RNA interference and overexpression, we show that altering brk expression within either the soma or the germline affects germ cell homeostasis. Remarkably, we find that Decapentaplegic (Dpp), the main BMP ligand and canonical antagonist of Brk, is upregulated by Brk in the escort cells of the germarium, demonstrating that Brk can positively regulate this pathway.
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Affiliation(s)
- Leslie Dunipace
- Division of Biology, California Institute of Technology, 1200 East California Boulevard, MC114-96, Pasadena, CA 91125, USA
| | - Susan Newcomb
- Division of Biology, California Institute of Technology, 1200 East California Boulevard, MC114-96, Pasadena, CA 91125, USA
| | - Angelike Stathopoulos
- Division of Biology, California Institute of Technology, 1200 East California Boulevard, MC114-96, Pasadena, CA 91125, USA
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10
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Casale AM, Cappucci U, Piacentini L. Unravelling HP1 functions: post-transcriptional regulation of stem cell fate. Chromosoma 2021; 130:103-111. [PMID: 34128099 PMCID: PMC8426308 DOI: 10.1007/s00412-021-00760-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 05/17/2021] [Accepted: 06/01/2021] [Indexed: 12/20/2022]
Abstract
Heterochromatin protein 1 (HP1) is a non-histone chromosomal protein first identified in Drosophila as a major component of constitutive heterochromatin, required for stable epigenetic gene silencing in many species including humans. Over the years, several studies have highlighted additional roles of HP1 in different cellular processes including telomere maintenance, DNA replication and repair, chromosome segregation and, surprisingly, positive regulation of gene expression. In this review, we briefly summarize past research and recent results supporting the unexpected and emerging role of HP1 in activating gene expression. In particular, we discuss the role of HP1 in post-transcriptional regulation of mRNA processing because it has proved decisive in the control of germline stem cells homeostasis in Drosophila and has certainly added a new dimension to our understanding on HP1 targeting and functions in epigenetic regulation of stem cell behaviour.
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Affiliation(s)
- Assunta Maria Casale
- Department of Biology and Biotechnology "C. Darwin", Sapienza University of Rome, Rome, Italy.
| | - Ugo Cappucci
- Department of Biology and Biotechnology "C. Darwin", Sapienza University of Rome, Rome, Italy
| | - Lucia Piacentini
- Department of Biology and Biotechnology "C. Darwin", Sapienza University of Rome, Rome, Italy.
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11
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Hu X, Li M, Hao X, Lu Y, Zhang L, Wu G. The Osa-Containing SWI/SNF Chromatin-Remodeling Complex Is Required in the Germline Differentiation Niche for Germline Stem Cell Progeny Differentiation. Genes (Basel) 2021; 12:genes12030363. [PMID: 33806269 PMCID: PMC7998989 DOI: 10.3390/genes12030363] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 02/23/2021] [Accepted: 02/25/2021] [Indexed: 12/22/2022] Open
Abstract
The Drosophila ovary is recognized as a powerful model to study stem cell self-renewal and differentiation. Decapentaplegic (Dpp) is secreted from the germline stem cell (GSC) niche to activate Bone Morphogenic Protein (BMP) signaling in GSCs for their self-renewal and is restricted in the differentiation niche for daughter cell differentiation. Here, we report that Switch/sucrose non-fermentable (SWI/SNF) component Osa depletion in escort cells (ECs) results in a blockage of GSC progeny differentiation. Further molecular and genetic analyses suggest that the defective germline differentiation is partially attributed to the elevated dpp transcription in ECs. Moreover, ectopic Engrailed (En) expression in osa-depleted ECs partially contributes to upregulated dpp transcription. Furthermore, we show that Osa regulates germline differentiation in a Brahma (Brm)-associated protein (BAP)-complex-dependent manner. Additionally, the loss of EC long cellular processes upon osa depletion may also partly contribute to the germline differentiation defect. Taken together, these data suggest that the epigenetic factor Osa plays an important role in controlling EC characteristics and germline lineage differentiation.
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Affiliation(s)
- Xiaolong Hu
- State Key Laboratory of Microbial Metabolism, The Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (X.H.); (M.L.)
| | - Mengjie Li
- State Key Laboratory of Microbial Metabolism, The Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (X.H.); (M.L.)
| | - Xue Hao
- State Key Laboratory of Cell Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, China; (X.H.); (Y.L.); (L.Z.)
| | - Yi Lu
- State Key Laboratory of Cell Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, China; (X.H.); (Y.L.); (L.Z.)
| | - Lei Zhang
- State Key Laboratory of Cell Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, China; (X.H.); (Y.L.); (L.Z.)
- School of Life Science and Technology, Shanghai Tech University, Shanghai 201210, China
- Bio-Research Innovation Center, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Suzhou 215121, China
| | - Geng Wu
- State Key Laboratory of Microbial Metabolism, The Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (X.H.); (M.L.)
- Correspondence:
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12
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Vidaurre V, Chen X. Epigenetic regulation of drosophila germline stem cell maintenance and differentiation. Dev Biol 2021; 473:105-118. [PMID: 33610541 DOI: 10.1016/j.ydbio.2021.02.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 01/26/2021] [Accepted: 02/06/2021] [Indexed: 12/13/2022]
Abstract
Gametogenesis is one of the most extreme cellular differentiation processes that takes place in Drosophila male and female germlines. This process begins at the germline stem cell, which undergoes asymmetric cell division (ACD) to produce a self-renewed daughter that preserves its stemness and a differentiating daughter cell that undergoes epigenetic and genomic changes to eventually produce haploid gametes. Research in molecular genetics and cellular biology are beginning to take advantage of the continually advancing genomic tools to understand: (1) how germ cells are able to maintain their identity throughout the adult reproductive lifetime, and (2) undergo differentiation in a balanced manner. In this review, we focus on the epigenetic mechanisms that address these two questions through their regulation of germline-soma communication to ensure germline stem cell identity and activity.
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Affiliation(s)
- Velinda Vidaurre
- Department of Biology, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Baltimore, MD, 21218, USA
| | - Xin Chen
- Department of Biology, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Baltimore, MD, 21218, USA.
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13
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Shi J, Jin Z, Yu Y, Zhang Y, Yang F, Huang H, Cai T, Xi R. A Progressive Somatic Cell Niche Regulates Germline Cyst Differentiation in the Drosophila Ovary. Curr Biol 2021; 31:840-852.e5. [PMID: 33340458 DOI: 10.1016/j.cub.2020.11.053] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 10/02/2020] [Accepted: 11/18/2020] [Indexed: 12/20/2022]
Abstract
In the germarium of the Drosophila ovary, developing germline cysts are surrounded by a population of somatic escort cells that are known to function as the niche cells for germline differentiation;1 however, the underlying molecular mechanisms of this niche function remain poorly understood. Through single-cell gene expression profiling combined with genetic analyses, we here demonstrate that the escort cells can be spatially and functionally divided into two successive domains. The anterior escort cells (aECs) specifically produce ecdysone, which acts on the cystoblast to promote synchronous cell division, whereas the posterior escort cells (pECs) respond to ecdysone signaling and regulate soma-germline cell adhesion to promote the transition from 16-cell cyst-to-egg chamber formation. The patterning of the aEC and pEC domains is independent of the germline but is dependent on JAK/STAT signaling activity, which emanates from the posterior. Thus, a heterogeneous population of escort cells constitutes a stepwise niche environment to orchestrate cystoblast division and differentiation toward egg chamber formation.
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14
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Wang M, Luan X, Yan Y, Zheng Q, Chen W, Fang J. Wnt6 regulates the homeostasis of the stem cell niche via Rac1-and Cdc42-mediated noncanonical Wnt signalling pathways in Drosophila testis. Exp Cell Res 2021; 402:112511. [PMID: 33582096 DOI: 10.1016/j.yexcr.2021.112511] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 01/18/2021] [Accepted: 01/26/2021] [Indexed: 11/23/2022]
Abstract
The homeostasis of the stem cell niche is regulated by both intrinsic and extrinsic factors, and the complex and ordered molecular and cellular regulatory mechanisms need to be further explored. In Drosophila testis, germline stem cells (GSCs) rely on hub cells for self-renewal and physical attachment. GSCs are also in contact with somatic cyst stem cells (CySCs). Utilizing genetic manipulation in Drosophila, we investigated the role of Wnt6 in vivo and in vitro. In Drosophila testis, we found that Wnt6 is required for GSC differentiation and CySC self-renewal. In Schneider 2 (S2) cells, we found that Wnt6 regulates cell proliferation and apoptosis. Mechanistically, we demonstrated that Wnt6 can downregulate the expression levels of Arm, Rac1 and Cdc42 in S2 cells. Notably, Rac1 and Cdc42, which act downstream of the noncanonical Wnt signalling pathway, imitated the phenotypes of Wnt6 in Drosophila testis. Thus, the newly discovered Wnt6-Rac1/Cdc42 signal axis is required for the homeostasis of the stem cell niche in the Drosophila testis.
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15
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Kalashnikova DA, Maksimov DA, Romanov SE, Laktionov PP, Koryakov DE. SetDB1 and Su(var)3-9 play non-overlapping roles in somatic cell chromosomes of Drosophila melanogaster. J Cell Sci 2021; 134:jcs.253096. [PMID: 33288549 DOI: 10.1242/jcs.253096] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 11/30/2020] [Indexed: 11/20/2022] Open
Abstract
We explored functional roles of two H3K9-specific histone methyltransferases of Drosophila melanogaster, SetDB1 (also known as Eggless) and Su(var)3-9. Using the DamID approach, we generated the binding profile for SetDB1 in Drosophila salivary gland chromosomes, and matched it to the profile of Su(var)3-9. Unlike Su(var)3-9, SetDB1 turned out to be an euchromatic protein that is absent from repeated DNA compartments, and is largely restricted to transcription start sites (TSSs) and 5' untranslated regions (5'UTRs) of ubiquitously expressed genes. Significant SetDB1 association is also observed at binding sites for the insulator protein CP190. SetDB1 and H3K9 di- and tri-methylated (me2 and me3)-enriched sites tend to display poor overlap. At the same time, SetDB1 has a clear connection with the distribution of H3K27me3 mark. SetDB1 binds outside the domains possessing this modification, and about half of the borders of H3K27me3 domains are decorated by SetDB1 together with actively transcribed genes. On the basis of poor correlation between the distribution of SetDB1 and H3K9 methylation marks, we speculate that, in somatic cells, SetDB1 may contribute to the methylation of a broader set of chromosomal proteins than just H3K9. In addition, SetDB1 can be expected to play a role in the establishment of chromatin functional domains.
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Affiliation(s)
| | - Daniil A Maksimov
- Institute of Molecular and Cellular Biology, Novosibirsk 630090, Russia
| | - Stanislav E Romanov
- Institute of Molecular and Cellular Biology, Novosibirsk 630090, Russia.,Laboratory of Epigenetics, Department of Natural Sciences, Novosibirsk State University, Novosibirsk 630090, Russia
| | - Petr P Laktionov
- Institute of Molecular and Cellular Biology, Novosibirsk 630090, Russia.,Laboratory of Epigenetics, Department of Natural Sciences, Novosibirsk State University, Novosibirsk 630090, Russia
| | - Dmitry E Koryakov
- Institute of Molecular and Cellular Biology, Novosibirsk 630090, Russia
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16
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Tu R, Duan B, Song X, Chen S, Scott A, Hall K, Blanck J, DeGraffenreid D, Li H, Perera A, Haug J, Xie T. Multiple Niche Compartments Orchestrate Stepwise Germline Stem Cell Progeny Differentiation. Curr Biol 2020; 31:827-839.e3. [PMID: 33357404 DOI: 10.1016/j.cub.2020.12.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 11/17/2020] [Accepted: 12/15/2020] [Indexed: 11/28/2022]
Abstract
The niche controls stem cell self-renewal and progenitor differentiation for maintaining adult tissue homeostasis in various organisms. However, it remains unclear whether the niche is compartmentalized to control stem cell self-renewal and stepwise progeny differentiation. In the Drosophila ovary, inner germarial sheath (IGS) cells form a niche for controlling germline stem cell (GSC) progeny differentiation. In this study, we have identified four IGS subpopulations, which form linearly arranged niche compartments for controlling GSC maintenance and multi-step progeny differentiation. Single-cell analysis of the adult ovary has identified four IGS subpopulations (IGS1-IGS4), the identities and cellular locations of which have been further confirmed by fluorescent in situ hybridization. IGS1 and IGS2 physically interact with GSCs and mitotic cysts to control GSC maintenance and cyst formation, respectively, whereas IGS3 and IGS4 physically interact with 16-cell cysts to regulate meiosis, oocyte development, and cyst morphological change. Finally, one follicle cell progenitor population has also been transcriptionally defined for facilitating future studies on follicle stem cell regulation. Therefore, this study has structurally revealed that the niche is organized into multiple compartments for orchestrating stepwise adult stem cell development and has also provided useful resources and tools for further functional characterization of the niche in the future.
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Affiliation(s)
- Renjun Tu
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Bo Duan
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Xiaoqing Song
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Shiyuan Chen
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Allison Scott
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Kate Hall
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Jillian Blanck
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Dustin DeGraffenreid
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Hua Li
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Anoja Perera
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Jeff Haug
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Ting Xie
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA; Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
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17
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Dutta P, Nath S, Li J, Li WX. Drosophila SERTAD domain protein Taranis is required in somatic cells for maintenance of male germline stem cells. Dev Dyn 2020; 250:237-248. [PMID: 32969117 DOI: 10.1002/dvdy.255] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/15/2020] [Accepted: 09/21/2020] [Indexed: 11/05/2022] Open
Abstract
BACKGROUND Polycomb proteins are essential for maintaining stem cell identity across different stem cell niches. However, how they function to maintain stem cell niches is not fully understood. RESULTS Here we show that the SERTAD protein Taranis (Tara), which is a Polycomb-trithorax group protein, is expressed in the adult testis niche and plays a role in its maintenance in Drosophila. We found that tara is expressed in early cyst cells, likely including somatic cyst stem cells (CySCs) of Drosophila male testis tip region, which houses both germline and somatic cyst stem cells along with the hub cells, forming the stem cell niche. Consistent with its expression, we found that, while loss of tara in germline cells only had minimal effects, tara knockdown in all cells or only in somatic cells of the niche reduced the number of not only somatic cells, but also germline stem cells (GSCs). We further found that Tara might antagonize Notch signaling in CySCs to maintain the stem cell niche. CONCLUSIONS Our studies suggest that Tara might function in somatic CySCs for GSC maintenance in the Drosophila testis.
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Affiliation(s)
- Pranabananda Dutta
- Department of Medicine, University of California San Diego, La Jolla, California, USA.,Division of Cancer Research and Training, Department of Medicine, Charles R. Drew University of Medicine and Science, Los Angeles, California, USA
| | - Soma Nath
- Department of Medicine, University of California San Diego, La Jolla, California, USA
| | - Jinghong Li
- Department of Medicine, University of California San Diego, La Jolla, California, USA
| | - Willis X Li
- Department of Medicine, University of California San Diego, La Jolla, California, USA
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18
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Waghmare I, Wang X, Page-McCaw A. Dally-like protein sequesters multiple Wnt ligands in the Drosophila germarium. Dev Biol 2020; 464:88-102. [PMID: 32473955 DOI: 10.1016/j.ydbio.2020.05.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 05/02/2020] [Accepted: 05/11/2020] [Indexed: 12/20/2022]
Abstract
Cells in multicellular organisms rely on secreted ligands for development and morphogenesis. Several mechanisms modulate the availability and distribution of secreted ligands, determining their ability to signal locally and at long range from their source. One of these mechanisms is Dally-like protein (Dlp), a cell-surface glypican that exhibits biphasic functions in Drosophila wing discs, promoting Wg signaling at long-range from Wg source cells and inhibiting Wg signaling near source cells. In the germarium at the tip of the ovary, Dlp promotes long-range distribution of Wg from cap cells to follicle stem cells. However, the germarium also expresses other Wnts - Wnt2, Wnt4, and Wnt6 - that function locally in escort cells to promote oogenesis. Whether and how local functions of these Wnts are regulated remains unknown. Here we show that the dlp overexpression phenotype is multifaceted and phenocopies multiple Wnt loss-of-function phenotypes. Each aspect of dlp overexpression phenotype is suppressed by co-expression of individual Wnts, and the suppression pattern exhibited by each Wnt suggests that Wnts have functional specificity in the germarium. Further, dlp knockdown phenocopies Wnt gain-of-function phenotypes. Together these data show that Dlp inhibits the functions of each Wnt. All four Wnts co-immunoprecipitate with Dlp in S2R+ cells, suggesting that in the germarium, Dlp sequesters Wnts to inhibit local paracrine Wnt signaling. Our results indicate that Dlp modulates the availability of multiple extracellular Wnts for local paracrine Wnt signaling in the germarium.
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Affiliation(s)
- Indrayani Waghmare
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA.
| | - Xiaoxi Wang
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Andrea Page-McCaw
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
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Tu R, Duan B, Song X, Xie T. Dlp-mediated Hh and Wnt signaling interdependence is critical in the niche for germline stem cell progeny differentiation. Sci Adv 2020; 6:eaaz0480. [PMID: 32426496 PMCID: PMC7220319 DOI: 10.1126/sciadv.aaz0480] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 02/28/2020] [Indexed: 05/04/2023]
Abstract
Although multiple signaling pathways work synergistically in various niches to control stem cell self-renewal and differentiation, it remains poorly understood how they cooperate with one another molecularly. In the Drosophila ovary, Hh and Wnt pathways function in the niche to promote germline stem cell (GSC) progeny differentiation. Here, we show that glypican Dlp-mediated Hh and Wnt signaling interdependence operates in the niche to promote GSC progeny differentiation by preventing BMP signaling. Hh/Wnt-mediated dlp repression is essential for their signaling interdependence in niche cells and for GSC progeny differentiation by preventing BMP signaling. Mechanistically, Hh and Wnt downstream transcription factors directly bind to the same dlp regulatory region and recruit corepressors composed of transcription factor Croc and Egg/H3K9 trimethylase to repress Dlp expression. Therefore, our study reveals a novel mechanism for Hh/Wnt signaling-mediated direct dlp repression and a novel regulatory mechanism for Dlp-mediated Hh/Wnt signaling interdependence in the GSC differentiation niche.
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Affiliation(s)
- Renjun Tu
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Bo Duan
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Xiaoqing Song
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Ting Xie
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
- Corresponding author.
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20
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Zhang H, Cai Y. Signal transduction pathways regulating Drosophila ovarian germline stem cells. Curr Opin Insect Sci 2020; 37:1-7. [PMID: 31726320 DOI: 10.1016/j.cois.2019.10.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 09/20/2019] [Accepted: 10/03/2019] [Indexed: 06/10/2023]
Abstract
Drosophila female germline stem cells (GSCs) serve as one of the best understood stem cell types. GSCs reside in a special microenvironment, the stem cell niche, and their activity is tightly regulated by niche-derived signals. In addition to the stemness-promoting signaling molecules, the niche also generates other signaling molecules that regulate GSC differentiation. Recent studies are beginning to appreciate the intricate interactions among these signaling molecules in the niche and their effects on GSC behaviour. This review summarizes recent advances to demonstrate how the niche functions as a signaling hub to integrate these niche-derived local signals as well as other organ-produced systemic signals to control GSC self-renewal and differentiation.
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Affiliation(s)
- Heng Zhang
- Temasek Life Sciences Laboratory, National University of Singapore, 117604, Singapore
| | - Yu Cai
- Temasek Life Sciences Laboratory, National University of Singapore, 117604, Singapore; Department of Biological Sciences, National University of Singapore, 117558, Singapore.
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21
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Kelleher ES, Lama J, Wang L. Uninvited guests: how transposable elements take advantage of Drosophila germline stem cells, and how stem cells fight back. Curr Opin Insect Sci 2020; 37:49-56. [PMID: 32113144 DOI: 10.1016/j.cois.2019.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 11/07/2019] [Accepted: 11/16/2019] [Indexed: 06/10/2023]
Abstract
Transposable elements (TEs) are mobile genetic parasites that spread through host genomes by replicating in germline cells. New TE copies that arise in the genomes of germline stem cells (GSCs) are of particular value, because they are potentially transmitted to multiple offspring through the plethora of gametes arising from the same progenitor GSC. However, the fidelity of GSC genomes is also of utmost importance to the host in ensuring the production of abundant and fit offspring. Here we review tactics that TEs employ to replicate in Drosophila female GSCs, as well as mechanisms those cells use to defend against TEs. We also discuss the relationship between transposition and GSC loss, which is arbitrated through reduced signaling for self renewal, increased signaling for differentiation, and DNA damage response pathways.
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Affiliation(s)
- Erin S Kelleher
- Department of Biology and Biochemistry, University of Houston, United States.
| | - Jyoti Lama
- Department of Biology and Biochemistry, University of Houston, United States
| | - Luyang Wang
- Department of Biology and Biochemistry, University of Houston, United States
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22
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Hsu HJ, Bahader M, Lai CM. Molecular control of the female germline stem cell niche size in Drosophila. Cell Mol Life Sci 2019; 76:4309-4317. [PMID: 31300869 DOI: 10.1007/s00018-019-03223-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 06/17/2019] [Accepted: 07/05/2019] [Indexed: 11/26/2022]
Abstract
Adult stem cells have a unique capacity to renew themselves and generate differentiated cells that are needed in the body. These cells are recruited and maintained by the surrounding microenvironment, known as the stem cell niche, during organ development. Thus, the stem cell niche is required for proper tissue homeostasis, and its dysregulation is associated with tumorigenesis and tissue degeneration. The identification of niche components and the mechanisms that regulate niche establishment and maintenance, however, are just beginning to be uncovered. Germline stem cells (GSCs) of the Drosophila ovary provide an excellent model for studying the stem cell niche in vivo because of their well-characterized cell biology and the availability of genetic tools. In this review, we introduce the ovarian GSC niche, and the key signaling pathways for niche precursor segregation, niche specification, and niche extracellular environment establishment and niche maintenance that are involved in regulating niche size during development and adulthood.
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Affiliation(s)
- Hwei-Jan Hsu
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, 11529, Taiwan.
| | - Majid Bahader
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, 11529, Taiwan
| | - Chun-Ming Lai
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, 11529, Taiwan
- Department of Developmental Biology, Sloan-Kettering Institute, 1275 York Ave, New York, NY, 10065, USA
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23
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Benner L, Castro EA, Whitworth C, Venken KJT, Yang H, Fang J, Oliver B, Cook KR, Lerit DA. Drosophila Heterochromatin Stabilization Requires the Zinc-Finger Protein Small Ovary. Genetics 2019; 213:877-895. [PMID: 31558581 PMCID: PMC6827387 DOI: 10.1534/genetics.119.302590] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 09/21/2019] [Indexed: 02/04/2023] Open
Abstract
Heterochromatin-mediated repression is essential for controlling the expression of transposons and for coordinated cell type-specific gene regulation. The small ovary (sov) locus was identified in a screen for female-sterile mutations in Drosophila melanogaster, and mutants show dramatic ovarian morphogenesis defects. We show that the null sov phenotype is lethal and map the locus to the uncharacterized gene CG14438, which encodes a nuclear zinc-finger protein that colocalizes with the essential Heterochromatin Protein 1 (HP1a). We demonstrate Sov functions to repress inappropriate gene expression in the ovary, silence transposons, and suppress position-effect variegation in the eye, suggesting a central role in heterochromatin stabilization.
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Affiliation(s)
- Leif Benner
- Section of Developmental Genomics, Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218
| | - Elias A Castro
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Cale Whitworth
- Section of Developmental Genomics, Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
- Department of Biology, Indiana University, Bloomington, Indiana 47405
| | - Koen J T Venken
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology
- McNair Medical Institute at the Robert and Janice McNair Foundation
- Dan L. Duncan Cancer Center, Center for Drug Discovery
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Haiwang Yang
- Section of Developmental Genomics, Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Junnan Fang
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Brian Oliver
- Section of Developmental Genomics, Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Kevin R Cook
- Department of Biology, Indiana University, Bloomington, Indiana 47405
| | - Dorothy A Lerit
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
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24
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Ren D, Guo W, Yang P, Song J, He J, Zhao L, Kang L. Structural and functional differentiation of a fat body-like tissue adhering to testis follicles facilitates spermatogenesis in locusts. Insect Biochem Mol Biol 2019; 113:103207. [PMID: 31421206 DOI: 10.1016/j.ibmb.2019.103207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 07/27/2019] [Accepted: 07/28/2019] [Indexed: 06/10/2023]
Abstract
The fat body is distributed throughout the body of insects, playing the essential role in intermediary metabolism and nutrient storage. However, the function of differentiation of fat bodies adhering to different tissues remains largely unknown. Here, we identified a fat body-like tissue (FLT) surrounding testis follicles and described its features at morphological, cellular and molecular levels. The FLT is morphologically distinguished with the abdominal fat body (FB) and dominated by diploid cells instead of polyploid cells. The transcriptomic analysis demonstrated that the FLT and FB have dramatically different gene expression profiles. Moreover, genes in the cell cycle pathway, which include both DNA replication- and cell division-related genes, were successively active during development of the FLT, suggesting that FLT cells possibly undergo a mitotic cycle rather than an endocycle. Deprivation of the FLT resulted in distortion of the testis follicles, disappearance of sperm bundles, reduction of total sperm number and increase of dead sperm, indicating a critical role of the FLT in the spermatogenesis in testis follicles. The special functional differentiation of the two similar tissues suggested that FLT-FB cells are able to establish a promising system to study mitotic-to-endocycle transition.
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Affiliation(s)
- Dani Ren
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Wei Guo
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Pengcheng Yang
- Beijing Institute of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Juan Song
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Jing He
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Lianfeng Zhao
- Beijing Institute of Life Science, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Le Kang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China; Beijing Institute of Life Science, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China.
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25
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Maksimov DA, Koryakov DE. Binding of SU(VAR)3-9 Partially Depends on SETDB1 in the Chromosomes of Drosophila melanogaster. Cells 2019; 8:cells8091030. [PMID: 31491894 PMCID: PMC6769583 DOI: 10.3390/cells8091030] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 09/03/2019] [Accepted: 09/03/2019] [Indexed: 02/06/2023] Open
Abstract
H3K9 methylation is known to play a critical role in gene silencing. This modification is established and maintained by several enzymes, but relationships between them are not fully understood. In the present study, we decipher the interplay between two Drosophila H3K9-specific histone methyltransferases, SU(VAR)3-9 and SETDB1. We asked whether SETDB1 is required for targeting of SU(VAR)3-9. Using DamID-seq, we obtained SU(VAR)3-9 binding profiles for the chromosomes from larval salivary glands and germline cells from adult females, and compared profiles between the wild type and SETDB1-mutant backgrounds. Our analyses indicate that the vast majority of single copy genes in euchromatin are targeted by SU(VAR)3-9 only in the presence of SETDB1, whereas SU(VAR)3-9 binding at repeated sequences in heterochromatin is largely SETDB1-independent. Interestingly, piRNA clusters 42AB and 38C in salivary gland chromosomes bind SU(VAR)3-9 regardless of SETDB1, whereas binding to the same regions in the germline cells is SETDB1-dependent. In addition, we compared SU(VAR)3-9 profiles in female germline cells at different developmental stages (germarium cells in juvenile ovaries and mature nurse cells). It turned out that SU(VAR)3-9 binding is influenced both by the presence of SETDB1, as well as by the differentiation stage.
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Affiliation(s)
- Daniil A Maksimov
- Institute of Molecular and Cellular Biology SB RAS, 630090 Novosibirsk, Russia.
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russia.
| | - Dmitry E Koryakov
- Institute of Molecular and Cellular Biology SB RAS, 630090 Novosibirsk, Russia.
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26
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Li M, Hu X, Zhang S, Ho MS, Wu G, Zhang L. Traffic jam regulates the function of the ovarian germline stem cell progeny differentiation niche during pre-adult stage in Drosophila. Sci Rep 2019; 9:10124. [PMID: 31300663 PMCID: PMC6626045 DOI: 10.1038/s41598-019-45317-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 03/29/2019] [Indexed: 11/28/2022] Open
Abstract
Stem cell self-renewal and the daughter cell differentiation are tightly regulated by the respective niches, which produce extrinsic cues to support the proper development. In Drosophila ovary, Dpp is secreted from germline stem cell (GSC) niche and activates the BMP signaling in GSCs for their self-renewal. Escort cells (ECs) in differentiation niche restrict Dpp outside the GSC niche and extend protrusions to help with proper differentiation of the GSC daughter cells. Here we provide evidence that loss of large Maf transcriptional factor Traffic jam (Tj) blocks GSC progeny differentiation. Spatio-temporal specific knockdown experiments indicate that Tj is required in pre-adult EC lineage for germline differentiation control. Further molecular and genetic analyses suggest that the defective germline differentiation caused by tj-depletion is partly attributed to the elevated dpp in the differentiation niche. Moreover, our study reveals that tj-depletion induces ectopic En expression outside the GSC niche, which contributes to the upregulated dpp expression in ECs as well as GSC progeny differentiation defect. Alternatively, loss of EC protrusions and decreased EC number elicited by tj-depletion may also partially contribute to the germline differentiation defect. Collectively, our findings suggest that Tj in ECs regulates germline differentiation by controlling the differentiation niche characteristics.
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Affiliation(s)
- Mengjie Li
- State Key Laboratory of Microbial Metabolism, School of Life Sciences & Biotechnology, The Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Xiaolong Hu
- State Key Laboratory of Microbial Metabolism, School of Life Sciences & Biotechnology, The Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Shu Zhang
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Margaret S Ho
- School of Life Science and Technology, Shanghai Tech University, Shanghai, 201210, China
| | - Geng Wu
- State Key Laboratory of Microbial Metabolism, School of Life Sciences & Biotechnology, The Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai, 200240, China.
| | - Lei Zhang
- State Key Laboratory of Cell Biology, CAS Center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China. .,School of Life Science and Technology, Shanghai Tech University, Shanghai, 201210, China.
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27
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Mao Y, Tu R, Huang Y, Mao D, Yang Z, Lau PK, Wang J, Ni J, Guo Y, Xie T. The exocyst functions in niche cells to promote germline stem cell differentiation by directly controlling EGFR membrane trafficking. Development 2019; 146:dev.174615. [PMID: 31142545 DOI: 10.1242/dev.174615] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 05/14/2019] [Indexed: 12/31/2022]
Abstract
The niche controls stem cell self-renewal and differentiation in animal tissues. Although the exocyst is known to be important for protein membrane trafficking and secretion, its role in stem cells and niches has never been reported. Here, this study shows that the exocyst functions in the niche to promote germline stem cell (GSC) progeny differentiation in the Drosophila ovary by directly regulating EGFR membrane trafficking and signaling. Inactivation of exocyst components in inner germarial sheath cells, which form the differentiation niche, causes a severe GSC differentiation defect. The exocyst is required for maintaining niche cells and preventing BMP signaling in GSC progeny by promoting EGFR membrane targeting and signaling through direct association with EGFR. Finally, it is also required for EGFR membrane targeting, recycling and signaling in human cells. Therefore, this study reveals a novel function of the exocyst in niche cells to promote stem cell progeny differentiation by directly controlling EGFR membrane trafficking and signaling in vivo, and also provides important insight into how the niche controls stem cell progeny differentiation at the molecular level.
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Affiliation(s)
- Ying Mao
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Renjun Tu
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Yan Huang
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Decai Mao
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Zhihao Yang
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Pik Ki Lau
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Jinhui Wang
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Jianquan Ni
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Yusong Guo
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Ting Xie
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
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28
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Kober L, Zimmermann M, Kurz M, Bayer M, Nagel AC. Loss of putzig in the germline impedes germ cell development by inducing cell death and new niche like microenvironments. Sci Rep 2019; 9:9108. [PMID: 31235815 DOI: 10.1038/s41598-019-45655-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 06/12/2019] [Indexed: 12/17/2022] Open
Abstract
Germline stem cell development and differentiation is tightly controlled by the surrounding somatic cells of the stem cell niche. In Drosophila females, cells of the niche emit various signals including Dpp and Wg to balance stem cell renewal and differentiation. Here, we show that the gene pzg is autonomously required in cells of the germline to sustain the interplay between niche and stem cells. Loss of pzg impairs stem cell differentiation and provokes the death of cells in the germarium. As a consequence of pzg loss, increased growth signalling activity predominantly of Dpp and Wg/Wnt, was observed, eventually disrupting the balance of germ cell self-renewal and differentiation. Whereas in the soma, apoptosis-induced compensatory growth is well established, the induction of self-renewal signals during oogenesis cannot compensate for dying germ cells, albeit inducing a new niche-like microenvironment. Instead, they impair the further development of germ cells and cause in addition a forward and feedback loop of cell death.
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Rechtsteiner A, Costello ME, Egelhofer TA, Garrigues JM, Strome S, Petrella LN. Repression of Germline Genes in Caenorhabditis elegans Somatic Tissues by H3K9 Dimethylation of Their Promoters. Genetics 2019; 212:125-140. [PMID: 30910798 PMCID: PMC6499516 DOI: 10.1534/genetics.118.301878] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 03/16/2019] [Indexed: 12/20/2022] Open
Abstract
Repression of germline-promoting genes in somatic cells is critical for somatic development and function. To study how germline genes are repressed in somatic tissues, we analyzed key histone modifications in three Caenorhabditis elegans synMuv B mutants, lin-15B, lin-35, and lin-37-all of which display ectopic expression of germline genes in the soma. LIN-35 and LIN-37 are members of the conserved DREAM complex. LIN-15B has been proposed to work with the DREAM complex but has not been shown biochemically to be a member of the complex. We found that, in wild-type worms, synMuv B target genes and germline genes are enriched for the repressive histone modification dimethylation of histone H3 on lysine 9 (H3K9me2) at their promoters. Genes with H3K9me2 promoter localization are evenly distributed across the autosomes, not biased toward autosomal arms, as are the broad H3K9me2 domains. Both synMuv B targets and germline genes display a dramatic reduction of H3K9me2 promoter localization in lin-15B mutants, but much weaker reduction in lin-35 and lin-37 mutants. This difference between lin-15B and DREAM complex mutants likely represents a difference in molecular function for these synMuv B proteins. In support of the pivotal role of H3K9me2 in regulation of germline genes by LIN-15B, global loss of H3K9me2 but not H3K9me3 results in phenotypes similar to synMuv B mutants, high-temperature larval arrest, and ectopic expression of germline genes in the soma. We propose that LIN-15B-driven enrichment of H3K9me2 at promoters of germline genes contributes to repression of those genes in somatic tissues.
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Affiliation(s)
- Andreas Rechtsteiner
- Department of Molecular, Cell, and Developmental Biology, University of California Santa Cruz, Santa Cruz, California 95064
| | - Meghan E Costello
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201
| | - Thea A Egelhofer
- Department of Molecular, Cell, and Developmental Biology, University of California Santa Cruz, Santa Cruz, California 95064
| | - Jacob M Garrigues
- Department of Molecular, Cell, and Developmental Biology, University of California Santa Cruz, Santa Cruz, California 95064
| | - Susan Strome
- Department of Molecular, Cell, and Developmental Biology, University of California Santa Cruz, Santa Cruz, California 95064
| | - Lisa N Petrella
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201
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30
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Seller CA, Cho CY, O'Farrell PH. Rapid embryonic cell cycles defer the establishment of heterochromatin by Eggless/SetDB1 in Drosophila. Genes Dev 2019; 33:403-417. [PMID: 30808658 PMCID: PMC6446540 DOI: 10.1101/gad.321646.118] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/14/2019] [Indexed: 12/15/2022]
Abstract
Acquisition of chromatin modifications during embryogenesis distinguishes different regions of an initially naïve genome. In many organisms, repetitive DNA is packaged into constitutive heterochromatin that is marked by di/trimethylation of histone H3K9 and the associated protein HP1a. These modifications enforce the unique epigenetic properties of heterochromatin. However, in the early Drosophila melanogaster embryo, the heterochromatin lacks these modifications, which appear only later, when rapid embryonic cell cycles slow down at the midblastula transition (MBT). Here we focus on the initial steps restoring heterochromatic modifications in the embryo. We describe the JabbaTrap, a technique for inactivating maternally provided proteins in embryos. Using the JabbaTrap, we reveal a major requirement for the methyltransferase Eggless/SetDB1 in the establishment of heterochromatin. In contrast, other methyltransferases contribute minimally. Live imaging reveals that endogenous Eggless gradually accumulates on chromatin in interphase but then dissociates in mitosis, and its accumulation must restart in the next cell cycle. Cell cycle slowing as the embryo approaches the MBT permits increasing accumulation and action of Eggless at its targets. Experimental manipulation of interphase duration shows that cell cycle speed regulates Eggless. We propose that developmental slowing of the cell cycle times embryonic heterochromatin formation.
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Affiliation(s)
- Charles A Seller
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Chun-Yi Cho
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Patrick H O'Farrell
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
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31
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Casale AM, Cappucci U, Fanti L, Piacentini L. Heterochromatin protein 1 (HP1) is intrinsically required for post-transcriptional regulation of Drosophila Germline Stem Cell (GSC) maintenance. Sci Rep 2019; 9:4372. [PMID: 30867469 DOI: 10.1038/s41598-019-40152-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 02/07/2019] [Indexed: 01/05/2023] Open
Abstract
A very important open question in stem cells regulation is how the fine balance between GSCs self-renewal and differentiation is orchestrated at the molecular level. In the past several years much progress has been made in understanding the molecular mechanisms underlying intrinsic and extrinsic controls of GSC regulation but the complex gene regulatory networks that regulate stem cell behavior are only partially understood. HP1 is a dynamic epigenetic determinant mainly involved in heterochromatin formation, epigenetic gene silencing and telomere maintenance. Furthermore, recent studies have revealed the importance of HP1 in DNA repair, sister chromatid cohesion and, surprisingly, in positive regulation of gene expression. Here, we show that HP1 plays a crucial role in the control of GSC homeostasis in Drosophila. Our findings demonstrate that HP1 is required intrinsically to promote GSC self-renewal and progeny differentiation by directly stabilizing the transcripts of key genes involved in GSCs maintenance.
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32
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Gao Y, Mao Y, Xu RG, Zhu R, Zhang M, Sun J, Shen D, Peng P, Xie T, Ni JQ. Defining gene networks controlling the maintenance and function of the differentiation niche by an in vivo systematic RNAi screen. J Genet Genomics 2019; 46:19-30. [PMID: 30745214 DOI: 10.1016/j.jgg.2018.10.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 10/02/2018] [Accepted: 10/23/2018] [Indexed: 01/13/2023]
Abstract
In the Drosophila ovary, escort cells (ECs) extrinsically control germline stem cell (GSC) maintenance and progeny differentiation. However, the underlying mechanisms remain poorly understood. In this study, we identified 173 EC genes for their roles in controlling GSC maintenance and progeny differentiation by using an in vivo systematic RNAi approach. Of the identified genes, 10 and 163 are required in ECs to promote GSC maintenance and progeny differentiation, respectively. The genes required for progeny differentiation fall into different functional categories, including transcription, mRNA splicing, protein degradation, signal transduction and cytoskeleton regulation. In addition, the GSC progeny differentiation defects caused by defective ECs are often associated with BMP signaling elevation, indicating that preventing BMP signaling is a general functional feature of the differentiation niche. Lastly, exon junction complex (EJC) components, which are essential for mRNA splicing, are required in ECs to promote GSC progeny differentiation by maintaining ECs and preventing BMP signaling. Therefore, this study has identified the major regulators of the differentiation niche, which provides important insights into how stem cell progeny differentiation is extrinsically controlled.
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Affiliation(s)
- Yuan Gao
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Ying Mao
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Rong-Gang Xu
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medicine, Tsinghua University, Beijing, 100084, China; Gene Regulatory Lab, School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Ruibao Zhu
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medicine, Tsinghua University, Beijing, 100084, China; Gene Regulatory Lab, School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Ming Zhang
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Jin Sun
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medicine, Tsinghua University, Beijing, 100084, China; Gene Regulatory Lab, School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Da Shen
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medicine, Tsinghua University, Beijing, 100084, China; Gene Regulatory Lab, School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Ping Peng
- PKU-THU Joint Center for Life Sciences, College of Life Sciences, School of Medicine, Tsinghua University, Beijing, 100084, China; Gene Regulatory Lab, School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Ting Xie
- Stowers Institute for Medical Research, 1000 East 50(th) Street, Kansas City, MO, 64110, USA.
| | - Jian-Quan Ni
- Gene Regulatory Lab, School of Medicine, Tsinghua University, Beijing, 100084, China; Tsingdao Advanced Research Institute, Tongji University, Qingdao, 266000, China.
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Yang F, Quan Z, Huang H, He M, Liu X, Cai T, Xi R. Ovaries absent links dLsd1 to HP1a for local H3K4 demethylation required for heterochromatic gene silencing. eLife 2019; 8:40806. [PMID: 30648969 PMCID: PMC6335052 DOI: 10.7554/elife.40806] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Accepted: 12/20/2018] [Indexed: 12/30/2022] Open
Abstract
Heterochromatin Protein 1 (HP1) is a conserved chromosomal protein in eukaryotic cells that has a major role in directing heterochromatin formation, a process that requires co-transcriptional gene silencing mediated by small RNAs and their associated argonaute proteins. Heterochromatin formation requires erasing the active epigenetic mark, such as H3K4me2, but the molecular link between HP1 and H3K4 demethylation remains unclear. In a fertility screen in female Drosophila, we identified ovaries absent (ova), which functions in the stem cell niche, downstream of Piwi, to support germline stem cell differentiation. Moreover, ova acts as a suppressor of position effect variegation, and is required for silencing telomeric transposons in the germline. Biochemically, Ova acts to link the H3K4 demethylase dLsd1 to HP1a for local histone modifications. Therefore, our study provides a molecular connection between HP1a and local H3K4 demethylation during HP1a-mediated gene silencing that is required for ovary development, transposon silencing, and heterochromatin formation. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter). The complete set of genetic material within a cell is known as a genome. The genomes of human and other animal cells have regions of active genes interspersed with ‘dark’ regions known as heterochromatin, which contain genes and other types of genetic material that have been inactivated. Heterochromatin commonly contains sections of genetic material known as transposons. When a transposon is active it is able to move around the genome, therefore, inactivating (or ‘silencing’) transposons helps to maintain the integrity of the genetic material in a cell. It is particularly important to silence transposons in the stem cells that produce sperm and egg cells – known as germline stem cells – to ensure genetic information is faithfully passed on to the next generation. A protein called HP1a plays a major role in directing where heterochromatin forms in the genome. This process requires an enzyme called dLsd1 to remove a small tag from the genetic material but it is not clear how HP1a regulates the activity of dLsd1. To address this question, Yang et al. studied how egg cells form in fruit flies, which are often used as models of animal biology in experiments. The team screened a population of fruit flies that carried mutations in many different genes to identify genes that affect the fertility of female flies. This revealed a gene named as ovaries absent (or ova for short) is required for egg cells to form. In germline stem cells ova silences transposons and in the surrounding tissue it represses a specific signal that usually maintains stem cells to allow the stem cells to divide to make egg cells. Further experiments using biochemical techniques found that the protein encoded by ova acts as a bridge to bring HP1a and dLsd1 together to silence genes in heterochromatin. The next step would be to identify the functional counterpart of the ova gene in mammals, including humans, which may help to discover causes of infertility and develop new fertility treatment.
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Affiliation(s)
- Fu Yang
- National Institute of Biological Sciences, Beijing, China
| | - Zhenghui Quan
- National Institute of Biological Sciences, Beijing, China
| | - Huanwei Huang
- National Institute of Biological Sciences, Beijing, China
| | - Minghui He
- National Institute of Biological Sciences, Beijing, China
| | - Xicheng Liu
- National Institute of Biological Sciences, Beijing, China
| | - Tao Cai
- National Institute of Biological Sciences, Beijing, China
| | - Rongwen Xi
- National Institute of Biological Sciences, Beijing, China.,Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing, China
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35
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Smolko AE, Shapiro-Kulnane L, Salz HK. The H3K9 methyltransferase SETDB1 maintains female identity in Drosophila germ cells. Nat Commun 2018; 9:4155. [PMID: 30297796 DOI: 10.1038/s41467-018-06697-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 09/19/2018] [Indexed: 12/17/2022] Open
Abstract
The preservation of germ cell sexual identity is essential for gametogenesis. Here we show that H3K9me3-mediated gene silencing is integral to female fate maintenance in Drosophila germ cells. Germ cell specific loss of the H3K9me3 pathway members, the H3K9 methyltransferase SETDB1, WDE, and HP1a, leads to ectopic expression of genes, many of which are normally expressed in testis. SETDB1 controls the accumulation of H3K9me3 over a subset of these genes without spreading into neighboring loci. At phf7, a regulator of male germ cell sexual fate, the H3K9me3 peak falls over the silenced testis-specific transcription start site. Furthermore, H3K9me3 recruitment to phf7 and repression of testis-specific transcription is dependent on the female sex determination gene Sxl. Thus, female identity is secured by an H3K9me3 epigenetic pathway in which Sxl is the upstream female-specific regulator, SETDB1 is the required chromatin writer, and phf7 is one of the critical SETDB1 target genes. Epigenetic regulation is critical for the maintenance of germ cell identity. Here the authors show that H3K9me3-mediated gene silencing is critical for repression of testis-specific transcription in Drosophila female germ cells, indicating H3K9me3 maintains female germ cell sexual identity.
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Abstract
Gametogenesis represents the most dramatic cellular differentiation pathways in both female and male flies. At the genome level, meiosis ensures that diploid germ cells become haploid gametes. At the epigenome level, extensive changes are required to turn on and shut off gene expression in a precise spatiotemporally controlled manner. Research applying conventional molecular genetics and cell biology, in combination with rapidly advancing genomic tools have helped us to investigate (1) how germ cells maintain lineage specificity throughout their adult reproductive lifetime; (2) what molecular mechanisms ensure proper oogenesis and spermatogenesis, as well as protect genome integrity of the germline; (3) how signaling pathways contribute to germline-soma communication; and (4) if such communication is important. In this chapter, we highlight recent discoveries that have improved our understanding of these questions. On the other hand, restarting a new life cycle upon fertilization is a unique challenge faced by gametes, raising questions that involve intergenerational and transgenerational epigenetic inheritance. Therefore, we also discuss new developments that link changes during gametogenesis to early embryonic development-a rapidly growing field that promises to bring more understanding to some fundamental questions regarding metazoan development.
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37
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Kang I, Choi Y, Jung S, Lim JY, Lee D, Gupta S, Moon W, Shin C. Identification of target genes regulated by the Drosophila histone methyltransferase Eggless reveals a role of Decapentaplegic in apoptotic signaling. Sci Rep 2018; 8:7123. [PMID: 29740006 PMCID: PMC5940877 DOI: 10.1038/s41598-018-25483-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 04/23/2018] [Indexed: 11/17/2022] Open
Abstract
Epigenetic gene regulation is essential for developmental processes. Eggless (Egg), the Drosophila orthologue of the mammalian histone methyltransferase, SETDB1, is known to be involved in the survival and differentiation of germline stem cells and piRNA cluster transcription during Drosophila oogenesis; however the detailed mechanisms remain to be determined. Here, using high-throughput RNA sequencing, we investigated target genes regulated by Egg in an unbiased manner. We show that Egg plays diverse roles in particular piRNA pathway gene expression, some long non-coding RNA expression, apoptosis-related gene regulation, and Decapentaplegic (Dpp) signaling during Drosophila oogenesis. Furthermore, using genetic and cell biological approaches, we demonstrate that ectopic upregulation of dpp caused by loss of Egg in the germarium can trigger apoptotic cell death through activation of two pro-apoptotic genes, reaper and head involution defective. We propose a model in which Egg regulates germ cell differentiation and apoptosis through canonical and noncanonical Dpp pathways in Drosophila oogenesis.
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Affiliation(s)
- Igojo Kang
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea
| | - Yourim Choi
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea
| | - Sueun Jung
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea
| | - Jae Yun Lim
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea
| | - Dooyoung Lee
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea
| | - Sumeet Gupta
- Whitehead Institute for Biomedical Research, Cambridge, 02142, MA, USA
| | - Woongjoon Moon
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea.
| | - Chanseok Shin
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea. .,Research Institute of Agriculture and Life Sciences, and Plant Genomics and Breeding Institute, Seoul National University, Seoul, 08826, Republic of Korea.
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38
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Waghmare I, Page-McCaw A. Wnt Signaling in Stem Cell Maintenance and Differentiation in the Drosophila Germarium. Genes (Basel) 2018; 9:genes9030127. [PMID: 29495453 PMCID: PMC5867848 DOI: 10.3390/genes9030127] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 02/13/2018] [Accepted: 02/14/2018] [Indexed: 01/19/2023] Open
Abstract
Wnt signaling is a conserved regulator of stem cell behaviors, and the Drosophila germarium has been an important model tissue for the study of stem cell maintenance, differentiation, and proliferation. Here we review Wnt signaling in the germarium, which houses two distinct types of ovarian stem cells: the anteriorly located germline stem cells (GSCs), which give rise to oocytes; and the mid-posteriorly located follicle stem cells (FSCs), which give rise to the somatic follicle cells that cover a developing oocyte. The maintenance and proliferation of GSCs and FSCs is regulated by the stem cell niches, whereas differentiation of the germline is regulated by the differentiation niche. Four distinct Wnt ligands are localized in the germarium, and we focus review on how these Wnt ligands and Wnt signaling affects maintenance and differentiation of both germline and follicle stem cells in their respective niches.
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Affiliation(s)
- Indrayani Waghmare
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA.
| | - Andrea Page-McCaw
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA.
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39
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Wang X, Page-McCaw A. Wnt6 maintains anterior escort cells as an integral component of the germline stem cell niche. Development 2018; 145:dev.158527. [PMID: 29361569 PMCID: PMC5818006 DOI: 10.1242/dev.158527] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 12/22/2017] [Indexed: 12/27/2022]
Abstract
Stem cells reside in a niche, a local environment whose cellular and molecular complexity is still being elucidated. In Drosophila ovaries, germline stem cells depend on cap cells for self-renewing signals and physical attachment. Germline stem cells also contact the anterior escort cells, and here we report that anterior escort cells are absolutely required for germline stem cell maintenance. When escort cells die from impaired Wnt signaling or hid expression, the loss of anterior escort cells causes loss of germline stem cells. Anterior escort cells function as an integral niche component by promoting DE-cadherin anchorage and by transiently expressing the Dpp ligand to promote full-strength BMP signaling in germline stem cells. Anterior escort cells are maintained by Wnt6 ligands produced by cap cells; without Wnt6 signaling, anterior escort cells die leaving vacancies in the niche, leading to loss of germline stem cells. Our data identify anterior escort cells as constituents of the germline stem cell niche, maintained by a cap cell-produced Wnt6 survival signal.
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Affiliation(s)
- Xiaoxi Wang
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Andrea Page-McCaw
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
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40
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Su YH, Rastegri E, Kao SH, Lai CM, Lin KY, Liao HY, Wang MH, Hsu HJ. Diet regulates membrane extension and survival of niche escort cells for germline homeostasis via insulin signaling. Development 2018; 145:dev.159186. [DOI: 10.1242/dev.159186] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Accepted: 03/09/2018] [Indexed: 12/29/2022]
Abstract
Diet is an important regulator of stem cell homeostasis, however, the underlying mechanisms of this regulation are not fully known. Here, we report that insulin signaling mediates dietary maintenance of Drosophila ovarian germline stem cells (GSCs) by promoting the extension of niche escort cell (EC) membranes to wrap around GSCs. This wrapping may facilitate the delivery of BMP stemness factors from ECs in the niche to GSCs. In addition to the effects on GSCs, insulin signaling-mediated regulation of EC number and protrusions controls the division and growth of GSC progeny. The effects of insulin signaling on EC membrane extension are, at least in part, driven by enhanced translation of Failed axon connections (Fax) via Ribosomal protein S6 kinase. Fax is a membrane protein that may participate in Abl-regulated cytoskeletal dynamics and is known to be involved in axon bundle formation. Therefore, we conclude that dietary cues stimulate insulin signaling in the niche to regulate EC cellular structure, probably via Fax-dependent cytoskeleton remodeling. This mechanism enhances intercellular contact and facilitates homeostatic interactions between somatic and germline cells in response to diet.
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Affiliation(s)
- Yu-Han Su
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Elham Rastegri
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei 11529, Taiwan
| | - Shih-Han Kao
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Chun-Min Lai
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica and National Chung-Hsing University, Taipei, 11529, Taiwan
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung 40227, Taiwan
- Biotechnology Center, National Chung-Hsing University, Taichung 40227, Taiwan
| | - Kun-Yang Lin
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica and National Chung-Hsing University, Taipei, 11529, Taiwan
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung 40227, Taiwan
- Biotechnology Center, National Chung-Hsing University, Taichung 40227, Taiwan
| | - Hung-Yu Liao
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Mu-Hsiang Wang
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Hwei-Jan Hsu
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei 11529, Taiwan
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung 40227, Taiwan
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41
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Jankovics F, Bence M, Sinka R, Faragó A, Bodai L, Pettkó-Szandtner A, Ibrahim K, Takács Z, Szarka-Kovács AB, Erdélyi M. Drosophila small ovary gene is required for transposon silencing and heterochromatin organisation and ensures germline stem cell maintenance and differentiation. Development 2018; 145:dev.170639. [DOI: 10.1242/dev.170639] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 10/29/2018] [Indexed: 12/17/2022]
Abstract
Self-renewal and differentiation of stem cells is one of the fundamental biological phenomena relying on proper chromatin organisation. In our study, we describe a novel chromatin regulator encoded by the Drosophila small ovary (sov) gene. We demonstrate that sov is required in both the germline stem cells (GSCs) and the surrounding somatic niche cells to ensure GSC survival and differentiation. Sov maintains niche integrity and function by repressing transposon mobility, not only in the germline, but also in the soma. Protein interactome analysis of Sov revealed an interaction between Sov and HP1a. In the germ cell nuclei, Sov co-localises with HP1a, suggesting that Sov affects transposon repression as a component of the heterochromatin. In a position effect variegation assay, we found a dominant genetic interaction between sov and HP1a, indicating their functional cooperation in promoting the spread of heterochromatin. An in vivo tethering assay and FRAP analysis revealed that Sov enhances heterochromatin formation by supporting the recruitment of HP1a to the chromatin. We propose a model in which sov maintains GSC niche integrity by regulating transposon silencing and heterochromatin formation.
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Affiliation(s)
- Ferenc Jankovics
- Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Melinda Bence
- Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Rita Sinka
- Department of Genetics, University of Szeged, Szeged, Hungary
| | - Anikó Faragó
- Department of Biochemistry and Molecular Biology, University of Szeged, Szeged, Hungary
| | - László Bodai
- Department of Biochemistry and Molecular Biology, University of Szeged, Szeged, Hungary
| | - Aladár Pettkó-Szandtner
- Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Karam Ibrahim
- Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Zsanett Takács
- Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | | | - Miklós Erdélyi
- Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
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42
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Salz HK, Dawson EP, Heaney JD. Germ cell tumors: Insights from the Drosophila ovary and the mouse testis. Mol Reprod Dev 2017; 84:200-211. [PMID: 28079292 DOI: 10.1002/mrd.22779] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/10/2017] [Indexed: 12/14/2022]
Abstract
Ovarian and testicular germ cell tumors of young adults are thought to arise from defects in germ cell development, but the molecular mechanisms underlying malignant transformation are poorly understood. In this review, we focus on the biology of germ cell tumor formation in the Drosophila ovary and the mouse testis, for which evidence supports common underlying mechanisms, such as blocking initiation into the differentiation pathway, impaired lineage progression, and sexual identity instability. We then discuss how these concepts inform our understanding of the disease in humans. Mol. Reprod. Dev. 84: 200-211, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Helen K Salz
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio
| | - Emily P Dawson
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas
| | - Jason D Heaney
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas
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43
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Luo L, Siah CK, Cai Y. Engrailed acts with Nejire to control decapentaplegic expression in the Drosophila ovarian stem cell niche. Development 2017; 144:3224-3231. [PMID: 28928281 DOI: 10.1242/dev.145474] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 08/01/2017] [Indexed: 12/30/2022]
Abstract
Homeostasis of adult tissues is maintained by a small number of stem cells, which are sustained by their niches. In the Drosophila female germline stem cell (GSC) niche, Decapentaplegic (Dpp) is the primary factor that promotes GSC self-renewal. However, the mechanism regulating dpp expression in the niche is largely unknown. Here, we identify a 2.0 kb fragment located in a 5' cis-regulatory region of the dpp locus containing enhancer activity that drives its expression in the niche. This region is distinct from a previously characterized 3' cis-regulatory enhancer responsible for dpp expression in imaginal discs. Our data demonstrate that Engrailed, a homeodomain-containing transcription factor that serves as a cap cell marker, binds to this region and regulates dpp expression in cap cells. Further data suggest that En forms a complex with Nejire (Nej), the Drosophila ortholog of histone acetyltransferase CBP/p300, and directs Nej to this cis-regulatory region where Nej functions as the co-activator for dpp expression. Therefore, our study defines the molecular pathway controlling dpp expression in the Drosophila ovarian stem cell niche.
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Affiliation(s)
- Lichao Luo
- Temasek Life Sciences Laboratory, National University of Singapore, 117604 Singapore.,Department of Biological Sciences, National University of Singapore, 117543 Singapore
| | - Chia Keng Siah
- Temasek Life Sciences Laboratory, National University of Singapore, 117604 Singapore
| | - Yu Cai
- Temasek Life Sciences Laboratory, National University of Singapore, 117604 Singapore .,Department of Biological Sciences, National University of Singapore, 117543 Singapore
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44
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Huang J, Reilein A, Kalderon D. Yorkie and Hedgehog independently restrict BMP production in escort cells to permit germline differentiation in the Drosophila ovary. Development 2017; 144:2584-2594. [PMID: 28619819 DOI: 10.1242/dev.147702] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 06/08/2017] [Indexed: 12/13/2022]
Abstract
Multiple signaling pathways guide the behavior and differentiation of both germline stem cells (GSCs) and somatic follicle stem cells (FSCs) in the Drosophila germarium, necessitating careful control of signal generation, range and responses. Signal integration involves escort cells (ECs), which promote differentiation of the GSC derivatives they envelop, provide niche signals for FSCs and derive directly from FSCs in adults. Hedgehog (Hh) signaling induces the Hippo pathway effector Yorkie (Yki) to promote proliferation and maintenance of FSCs, but Hh also signals to ECs, which are quiescent. Here, we show that in ECs both Hh and Yki limit production of BMP ligands to allow germline differentiation. Loss of Yki produced a more severe germarial phenotype than loss of Hh signaling and principally induced a different BMP ligand. Moreover, Yki activity reporters and epistasis tests showed that Yki does not mediate the key actions of Hh signaling in ECs. Thus, both the coupling and output of the Hh and Yki signaling pathways differ between FSCs and ECs despite their proximity and the fact that FSCs give rise directly to ECs.
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Affiliation(s)
- Jianhua Huang
- State Key Laboratory of Rice Biology, Institute of Insect Sciences, Zhejiang University, Hangzhou, 310058, China.,Department of Biological Sciences, Columbia University, 1212 Amsterdam Ave., New York, NY 10027, USA
| | - Amy Reilein
- Department of Biological Sciences, Columbia University, 1212 Amsterdam Ave., New York, NY 10027, USA
| | - Daniel Kalderon
- Department of Biological Sciences, Columbia University, 1212 Amsterdam Ave., New York, NY 10027, USA
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45
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Yang Z, Sun J, Hu Y, Wang F, Wang X, Qiao HH, Xu J, Mao D, Ren X, Pan LX, Xu RG, Xu BW, Zhang Y, Li H, Miao W, Hu Y, Chang Z, Wang D, Li H, Chang Z, Liu LP, Liu Q, Ni JQ. Histone H1 defect in escort cells triggers germline tumor in Drosophila ovary. Dev Biol 2017; 424:40-9. [PMID: 28232075 DOI: 10.1016/j.ydbio.2017.02.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 02/19/2017] [Accepted: 02/19/2017] [Indexed: 12/19/2022]
Abstract
Drosophila ovary is recognized as one of the best model systems to study stem cell biology in vivo. We had previously identified an autonomous role of the histone H1 in germline stem cell (GSC) maintenance. Here, we found that histone H1 depletion in escort cells (ECs) resulted in an increase of spectrosome-containing cells (SCCs), an ovary tumor-like phenotype. Further analysis showed that the Dpp pathway is excessively activated in these SCC cells, while the expression of bam is attenuated. In the H1-depleted ECs, both transposon activity and DNA damage had increased dramatically, followed by EC apoptosis, which is consistent with the role of H1 in other somatic cells. Surprisingly, H1-depleted ECs acquired cap cell characteristics including dpp expression, and the resulting abnormal Dpp level inhibits SCC further differentiation. Most interestingly, double knockdown of H1 and dpp in ECs can reduce the number of SCCs to the normal level, indicating that the additional Dpp secreted by ECs contributes to the germline tumor. Taken together, our findings indicate that histone H1 is an important epigenetic factor in controlling EC characteristics and a key suppressor of germline tumor.
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46
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Li X, Yang F, Chen H, Deng B, Li X, Xi R. Control of germline stem cell differentiation by Polycomb and Trithorax group genes in the niche microenvironment. Development 2016; 143:3449-3458. [PMID: 27510973 DOI: 10.1242/dev.137638] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 07/29/2016] [Indexed: 12/30/2022]
Abstract
Polycomb and Trithorax group (PcG and TrxG) genes function to regulate gene transcription by maintaining a repressive or active chromatin state, respectively. This antagonistic activity is important for body patterning during embryonic development, but whether this function module has a role in adult tissues is unclear. Here, we report that in the Drosophila ovary, disruption of the Polycomb repressive complex 1 (PRC1), specifically in the supporting escort cells, causes blockage of cystoblast differentiation and germline stem cell-like tumor formation. Tumors are caused by derepression of decapentaplegic (dpp), which prevents cystoblast differentiation. Interestingly, activation of dpp in escort cells requires the function of the TrxG gene brahma (brm), suggesting that loss of PRC1 in escort cells causes Brm-dependent dpp expression. Our study suggests a requirement for balanced activity between PcG and TrxG in an adult stem cell niche, and disruption of this balance could lead to the loss of tissue homeostasis and tumorigenesis.
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Affiliation(s)
- Xuewen Li
- College of Biological Sciences, China Agricultural University, Beijing 100193, China National Institute of Biological Sciences, No. 7 Science Park Road, Zhongguancun Life Science Park, Beijing 102206, China
| | - Fu Yang
- National Institute of Biological Sciences, No. 7 Science Park Road, Zhongguancun Life Science Park, Beijing 102206, China
| | - Hongyan Chen
- National Institute of Biological Sciences, No. 7 Science Park Road, Zhongguancun Life Science Park, Beijing 102206, China
| | - Bowen Deng
- National Institute of Biological Sciences, No. 7 Science Park Road, Zhongguancun Life Science Park, Beijing 102206, China
| | - Xinghua Li
- National Institute of Biological Sciences, No. 7 Science Park Road, Zhongguancun Life Science Park, Beijing 102206, China
| | - Rongwen Xi
- National Institute of Biological Sciences, No. 7 Science Park Road, Zhongguancun Life Science Park, Beijing 102206, China
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47
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Shinoda N, Obata F, Zhang L, Miura M. Drosophila SETDB1 and caspase cooperatively fine-tune cell fate determination of sensory organ precursor. Genes Cells 2016; 21:378-86. [PMID: 26914287 DOI: 10.1111/gtc.12348] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 01/06/2016] [Indexed: 12/18/2022]
Abstract
Drosophila produce a constant number of mechanosensory bristles called macrochaetae (MC), which develop from sensory organ precursor (SOP) cells within a proneural cluster (PNC). However, what ensures the precise determination of SOP cells remains to be elucidated. In this study, we conducted RNAi screening in PNC for genes involved in epigenetic regulation. We identified a H3K9 histone methyltransferase, SETDB1/eggless, as a regulator of SOP development. Knockdown of SETDB1 in PNC led to additional SOPs. We further tested the relationship between SETDB1 and non-apoptotic function of caspase on SOP development. Reinforcing caspase activation by heterozygous Drosophila inhibitor of apoptosis protein 1 (DIAP1) mutation rescued ectopic SOP development caused by SETDB1 knockdown. Knockdown of SETDB1, however, had little effect on caspase activity. Simultaneous loss of SETDB1 and caspase activity resulted in further increase in MC, indicating that the two components work cooperatively. Our study suggests the fine-tuning mechanisms for SOP development by epigenetic methyltransferase and non-apoptotic caspase function.
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Affiliation(s)
- Natsuki Shinoda
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Fumiaki Obata
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Liu Zhang
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masayuki Miura
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.,Agency for Medical Research and Development-Core Research for Evolutional Medical Science and Technology (AMED-CREST), Japan Agency for Medical Research and Development, 20F Yomiuri Shimbun Building 1-7-1 Otemachi, Chiyoda-ku, Tokyo 100-0004, Japan
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48
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Liu Z, Zhong G, Chai PC, Luo L, Liu S, Yang Y, Baeg GH, Cai Y. Coordinated niche-associated signals promote germline homeostasis in the Drosophila ovary. J Cell Biol 2016; 211:469-84. [PMID: 26504174 PMCID: PMC4621830 DOI: 10.1083/jcb.201503033] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Stem cell niches provide localized signaling molecules to promote stem cell fate and to suppress differentiation. The Drosophila melanogaster ovarian niche is established by several types of stromal cells, including terminal filament cells, cap cells, and escort cells (ECs). Here, we show that, in addition to its well-known function as a niche factor expressed in cap cells, the Drosophila transforming growth factor β molecule Decapentaplegic (Dpp) is expressed at a low level in ECs to maintain a pool of partially differentiated germline cells that may dedifferentiate to replenish germline stem cells upon their depletion under normal and stress conditions. Our study further reveals that the Dpp level in ECs is modulated by Hedgehog (Hh) ligands, which originate from both cap cells and ECs. We also demonstrate that Hh signaling exerts its function by suppressing Janus kinase/signal transducer activity, which promotes Dpp expression in ECs. Collectively, our data suggest a complex interplay of niche-associated signals that controls the development of a stem cell lineage.
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Affiliation(s)
- Zhong Liu
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604
| | - Guohua Zhong
- Laboratory of Insect Toxicology, South China Agriculture University, Guangzhou, PR China 510642
| | - Phing Chian Chai
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604
| | - Lichao Luo
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 Department of Biological Sciences, National University of Singapore, Singapore 117543
| | - Sen Liu
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604
| | - Ying Yang
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 Department of Biological Sciences, National University of Singapore, Singapore 117543
| | - Gyeong-Hun Baeg
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597
| | - Yu Cai
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 Department of Biological Sciences, National University of Singapore, Singapore 117543
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49
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Lu T, Wang S, Gao Y, Mao Y, Yang Z, Liu L, Song X, Ni J, Xie T. COP9-Hedgehog axis regulates the function of the germline stem cell progeny differentiation niche in the Drosophila ovary. Development 2015; 142:4242-52. [DOI: 10.1242/dev.124768] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Both stem cell self-renewal and lineage differentiation are controlled extrinsically as well as intrinsically. Germline stem cells (GSCs) in the Drosophila ovary provide an attractive model in which to study both stem cell self-renewal and lineage differentiation at the molecular and cellular level. Recently, we have proposed that escort cells (ECs) form a differentiation niche to control GSC lineage specification extrinsically. However, it remains poorly understood how the maintenance and function of the differentiation niche are regulated at the molecular level. Here, this study reveals a new role of COP9 in the differentiation niche to modulate autocrine Hedgehog (Hh) signaling, thereby promoting GSC lineage differentiation. COP9, which is a highly conserved protein complex composed of eight CSN subunits, catalyzes the removal of Nedd8 protein modification from target proteins. Our genetic results have demonstrated that all the COP9 components and the hh pathway components, including hh itself, are required in ECs to promote GSC progeny differentiation. Interestingly, COP9 is required in ECs to maintain Hh signaling activity, and activating Hh signaling in ECs can partially bypass the requirement for COP9 in GSC progeny differentiation. Finally, both COP9 and Hh signaling in ECs promote GSC progeny differentiation partly by preventing BMP signaling and maintaining cellular processes. Therefore, this study has demonstrated that the COP9-Hh signaling axis operates in the differentiation niche to promote GSC progeny differentiation partly by maintaining EC cellular processes and preventing BMP signaling. This provides new insight into how the function of the differentiation niche is regulated at the molecular level.
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Affiliation(s)
- Tinglin Lu
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Su Wang
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, 3901 Rainbow Blvd, Kansas City, KS 66160, USA
| | - Yuan Gao
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ying Mao
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Zhihao Yang
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Luping Liu
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xiaoqing Song
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Jianquan Ni
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ting Xie
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, 3901 Rainbow Blvd, Kansas City, KS 66160, USA
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50
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Abstract
Stem cell maintenance requires expression of genes essential for stemness and repression of differentiation genes. How this is achieved remains incompletely understood. Here we investigate the requirement for central components of heterochromatin, Heterochromatin Protein 1 (HP1) and the histone H3 lys9 methyltransferase Su(var)3-9, in the Drosophila male germline stem cell (GSC) self-renewal, a paradigm for studying adult stem cell behavior. We found that mutations or RNAi knock down of HP1 or Su(var)3-9 cause loss of GSCs, accompanied by defects in cell division or survival and premature expression of the differentiation gene bag of marbles (bam). Conversely, over-expressing HP1 increases GSC number in wildtype flies and, strikingly, restores fertility to the sterile hopscotch (hop) mutant flies that lack niche signals. These results suggest that the central components of heterochromatin play roles including repressing differentiation genes in Drosophila male GSC maintenance.
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