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Histone H1-mediated epigenetic regulation controls germline stem cell self-renewal by modulating H4K16 acetylation. Nat Commun 2015; 6:8856. [PMID: 26581759 PMCID: PMC4673494 DOI: 10.1038/ncomms9856] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 10/12/2015] [Indexed: 12/29/2022] Open
Abstract
Epigenetics plays critical roles in controlling stem cell self-renewal and differentiation. Histone H1 is one of the most critical chromatin regulators, but its role in adult stem cell regulation remains unclear. Here we report that H1 is intrinsically required in the regulation of germline stem cells (GSCs) in the Drosophila ovary. The loss of H1 from GSCs causes their premature differentiation through activation of the key GSC differentiation factor bam. Interestingly, the acetylated H4 lysine 16 (H4K16ac) is selectively augmented in the H1-depleted GSCs. Furthermore, overexpression of mof reduces H1 association on chromatin. In contrast, the knocking down of mof significantly rescues the GSC loss phenotype. Taken together, these results suggest that H1 functions intrinsically to promote GSC self-renewal by antagonizing MOF function. Since H1 and H4K16 acetylation are highly conserved from fly to human, the findings from this study might be applicable to stem cells in other systems. Epigenetics plays critical roles in controlling stem cell self-renewal and differentiation. Here, Sun et al. show that H1 is intrinsically required in the regulation of germline stem cells in the Drosophila ovary by antagonizing MOF, a histone acetyltransferase specific for H4K16.
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Wang S, Gao Y, Song X, Ma X, Zhu X, Mao Y, Yang Z, Ni J, Li H, Malanowski KE, Anoja P, Park J, Haug J, Xie T. Wnt signaling-mediated redox regulation maintains the germ line stem cell differentiation niche. eLife 2015; 4:e08174. [PMID: 26452202 PMCID: PMC4598714 DOI: 10.7554/elife.08174] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 09/12/2015] [Indexed: 12/21/2022] Open
Abstract
Adult stem cells continuously undergo self-renewal and generate differentiated cells. In the Drosophila ovary, two separate niches control germ line stem cell (GSC) self-renewal and differentiation processes. Compared to the self-renewing niche, relatively little is known about the maintenance and function of the differentiation niche. In this study, we show that the cellular redox state regulated by Wnt signaling is critical for the maintenance and function of the differentiation niche to promote GSC progeny differentiation. Defective Wnt signaling causes the loss of the differentiation niche and the upregulated BMP signaling in differentiated GSC progeny, thereby disrupting germ cell differentiation. Mechanistically, Wnt signaling controls the expression of multiple glutathione-S-transferase family genes and the cellular redox state. Finally, Wnt2 and Wnt4 function redundantly to maintain active Wnt signaling in the differentiation niche. Therefore, this study has revealed a novel strategy for Wnt signaling in regulating the cellular redox state and maintaining the differentiation niche. DOI:http://dx.doi.org/10.7554/eLife.08174.001 An animal or plant has many different types of cells that have specific roles in the life of the organism. These cells are organized into tissues. In most tissues in adult animals, small groups of cells called stem cells are responsible for replacing the other cells that have been lost due to disease, injury, or as part of normal body maintenance. The ‘germ line’ stem cells of female fruit flies—which produce female sex cells (or eggs)—are an effective system for studying how stem cells are regulated. These cells live in an area of the ovary called a stem cell niche. Each time a stem cell divides, it produces one stem cell and one other daughter cell. This daughter cell then moves into another niche called the ‘differentiation’ niche and undergoes a series of divisions that produce the egg cells. The differentiation niche is formed by escort cells and is crucial for producing the egg cells, but it is not clear how the escort cells promote this process, or how the niche is maintained. Wang et al. have now studied the differentiation niche in more detail. The experiments show that a cell communication system called Wnt signaling maintains the differentiation niche by controlling the ability of the escort cells to grow and divide. If Wnt signaling is defective, the differentiation niche is lost, which disrupts the formation of egg cells. Further experiments show that two proteins called Wnt2 and Wnt4 in the differentiation niche—which activate Wnt signaling—act as signals to regulate the niche, mainly by controlling the expression of four particular genes. These four genes encode enzymes that remove ‘reactive oxygen species’ from cells. Wang et al.'s findings have revealed an important role for Wnt signaling in maintaining the differentiation niche. The next step is to figure out the details of how this works. DOI:http://dx.doi.org/10.7554/eLife.08174.002
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Affiliation(s)
- Su Wang
- Stowers Institute for Medical Research, Kansas City, United States.,Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, United States
| | - Yuan Gao
- Center for Life Sciences, College of Life Sciences, School of Medical Sciences, Tsinghua University, Beijing, China
| | - Xiaoqing Song
- Stowers Institute for Medical Research, Kansas City, United States
| | - Xing Ma
- Stowers Institute for Medical Research, Kansas City, United States.,Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, United States
| | - Xiujuan Zhu
- Stowers Institute for Medical Research, Kansas City, United States
| | - Ying Mao
- Center for Life Sciences, College of Life Sciences, School of Medical Sciences, Tsinghua University, Beijing, China
| | - Zhihao Yang
- Center for Life Sciences, College of Life Sciences, School of Medical Sciences, Tsinghua University, Beijing, China
| | - Jianquan Ni
- Center for Life Sciences, College of Life Sciences, School of Medical Sciences, Tsinghua University, Beijing, China
| | - Hua Li
- Stowers Institute for Medical Research, Kansas City, United States
| | | | - Perera Anoja
- Stowers Institute for Medical Research, Kansas City, United States
| | - Jungeun Park
- Stowers Institute for Medical Research, Kansas City, United States
| | - Jeff Haug
- Stowers Institute for Medical Research, Kansas City, United States
| | - Ting Xie
- Stowers Institute for Medical Research, Kansas City, United States.,Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, United States
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53
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Luo L, Wang H, Fan C, Liu S, Cai Y. Wnt ligands regulate Tkv expression to constrain Dpp activity in the Drosophila ovarian stem cell niche. ACTA ACUST UNITED AC 2015; 209:595-608. [PMID: 26008746 PMCID: PMC4442805 DOI: 10.1083/jcb.201409142] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Multiple Wnt ligands produced by cap cells regulate the expression of Tkv, which acts as a receptor sink to remove excess cap cell–expressed Dpp and to restrict niche-associated Dpp activity, in escort cells. Stem cell self-renewal versus differentiation is regulated by the niche, which provides localized molecules that favor self-renewal. In the Drosophila melanogaster female germline stem cell (GSC) niche, Decapentaplegic (Dpp), a fly transforming growth factor β molecule and well-established long-range morphogen, acts over one cell diameter to maintain the GSCs. Here, we show that Thickveins (Tkv; a type I receptor of Dpp) is highly expressed in stromal cells next to Dpp-producing cells and functions to remove excess Dpp outside the niche, thereby spatially restricting its activity. Interestingly, Tkv expression in these stromal cells is regulated by multiple Wnt ligands that are produced by the niche. Our data demonstrate a self-restraining mechanism by which the Drosophila ovarian GSC niche acts to define its own boundary.
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Affiliation(s)
- Lichao Luo
- Temasek Life Sciences Laboratory and Department of Biological Sciences, National University of Singapore, Singapore, 117604 Temasek Life Sciences Laboratory and Department of Biological Sciences, National University of Singapore, Singapore, 117604
| | - Huashan Wang
- Temasek Life Sciences Laboratory and Department of Biological Sciences, National University of Singapore, Singapore, 117604
| | - Chao Fan
- Temasek Life Sciences Laboratory and Department of Biological Sciences, National University of Singapore, Singapore, 117604
| | - Sen Liu
- Temasek Life Sciences Laboratory and Department of Biological Sciences, National University of Singapore, Singapore, 117604
| | - Yu Cai
- Temasek Life Sciences Laboratory and Department of Biological Sciences, National University of Singapore, Singapore, 117604 Temasek Life Sciences Laboratory and Department of Biological Sciences, National University of Singapore, Singapore, 117604
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Fei Q, Yang X, Jiang H, Wang Q, Yu Y, Yu Y, Yi W, Zhou S, Chen T, Lu C, Atadja P, Liu XS, Li E, Zhang Y, Shou J. SETDB1 modulates PRC2 activity at developmental genes independently of H3K9 trimethylation in mouse ES cells. Genome Res 2015; 25:1325-35. [PMID: 26160163 PMCID: PMC4561491 DOI: 10.1101/gr.177576.114] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 07/08/2015] [Indexed: 11/25/2022]
Abstract
SETDB1, a histone methyltransferase responsible for methylation of histone H3 lysine 9 (H3K9), is involved in maintenance of embryonic stem (ES) cells and early embryonic development of the mouse. However, how SETDB1 regulates gene expression during development is largely unknown. Here, we characterized genome-wide SETDB1 binding and H3K9 trimethylation (H3K9me3) profiles in mouse ES cells and uncovered two distinct classes of SETDB1 binding sites, termed solo and ensemble peaks. The solo peaks were devoid of H3K9me3 and enriched near developmental regulators while the ensemble peaks were associated with H3K9me3. A subset of the SETDB1 solo peaks, particularly those near neural development–related genes, was found to be associated with Polycomb Repressive Complex 2 (PRC2) as well as PRC2-interacting proteins JARID2 and MTF2. Genetic deletion of Setdb1 reduced EZH2 binding as well as histone 3 lysine 27 (H3K27) trimethylation level at SETDB1 solo peaks and facilitated neural differentiation. Furthermore, we found that H3K27me3 inhibits SETDB1 methyltransferase activity. The currently identified reciprocal action between SETDB1 and PRC2 reveals a novel mechanism underlying ES cell pluripotency and differentiation regulation.
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Affiliation(s)
- Qi Fei
- China Novartis Institutes for BioMedical Research, Shanghai 201203, China
| | - Xiaoqin Yang
- Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai 200092, China
| | - Hua Jiang
- China Novartis Institutes for BioMedical Research, Shanghai 201203, China
| | - Qian Wang
- Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai 200092, China
| | - Yanyan Yu
- China Novartis Institutes for BioMedical Research, Shanghai 201203, China
| | - Yiling Yu
- China Novartis Institutes for BioMedical Research, Shanghai 201203, China
| | - Wei Yi
- China Novartis Institutes for BioMedical Research, Shanghai 201203, China
| | - Shaolian Zhou
- China Novartis Institutes for BioMedical Research, Shanghai 201203, China
| | - Taiping Chen
- Novartis Institutes for BioMedical Research, Cambridge, Massachusetts 02139, USA
| | - Chris Lu
- China Novartis Institutes for BioMedical Research, Shanghai 201203, China
| | - Peter Atadja
- China Novartis Institutes for BioMedical Research, Shanghai 201203, China
| | - Xiaole Shirley Liu
- Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Harvard School of Public Health, Boston, Massachusetts 02115, USA
| | - En Li
- China Novartis Institutes for BioMedical Research, Shanghai 201203, China
| | - Yong Zhang
- Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai 200092, China
| | - Jianyong Shou
- China Novartis Institutes for BioMedical Research, Shanghai 201203, China
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55
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Feng L, Chen X. Epigenetic regulation of germ cells-remember or forget? Curr Opin Genet Dev 2015; 31:20-7. [PMID: 25930104 DOI: 10.1016/j.gde.2015.04.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 04/02/2015] [Indexed: 12/18/2022]
Abstract
Unlike somatic cells, germ cells retain the potential to reproduce an entire new organism upon fertilization. In order to accomplish the process of fertilization, germ cells undergo an extreme cellular differentiation process known as gametogenesis in order to produce morphologically and functionally distinct oocyte and sperm. In addition to changes in genetic content changes from diploid to haploid, epigenetic mechanisms that modify chromatin state without altering primary DNA sequences have profound influence on germ cell differentiation and moreover, the transgenerational effect. In this review, we will go over the most recent discoveries on epigenetic regulations in germline differentiation and transgenerational inheritance across different metazoan species.
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Affiliation(s)
- Lijuan Feng
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, United States
| | - Xin Chen
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, United States.
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56
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Abstract
Stem cells give rise to tissues and organs during development and maintain their integrity during adulthood. They have the potential to self-renew or differentiate at each division. To ensure proper organ growth and homeostasis, self-renewal versus differentiation decisions need to be tightly controlled. Systematic genetic studies in Drosophila melanogaster are revealing extensive regulatory networks that control the switch between stem cell self-renewal and differentiation in the germline. These networks, which are based primarily on mutual translational repression, act via interlocked feedback loops to provide robustness to this important fate decision.
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Affiliation(s)
- Maija Slaidina
- Howard Hughes Medical Institute and Kimmel Center for Biology and Medicine of the Skirball Institute, Department of Cell Biology, New York University School of Medicine, New York, NY 10016 Howard Hughes Medical Institute and Kimmel Center for Biology and Medicine of the Skirball Institute, Department of Cell Biology, New York University School of Medicine, New York, NY 10016
| | - Ruth Lehmann
- Howard Hughes Medical Institute and Kimmel Center for Biology and Medicine of the Skirball Institute, Department of Cell Biology, New York University School of Medicine, New York, NY 10016 Howard Hughes Medical Institute and Kimmel Center for Biology and Medicine of the Skirball Institute, Department of Cell Biology, New York University School of Medicine, New York, NY 10016
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57
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König A, Shcherbata HR. Soma influences GSC progeny differentiation via the cell adhesion-mediated steroid-let-7-Wingless signaling cascade that regulates chromatin dynamics. Biol Open 2015; 4:285-300. [PMID: 25661868 PMCID: PMC4359735 DOI: 10.1242/bio.201410553] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
It is known that signaling from the germline stem cell niche is required to maintain germline stem cell identity in Drosophila. However, it is not clear whether the germline stem-cell daughters differentiate by default (because they are physically distant from the niche) or whether additional signaling is necessary to initiate the differentiation program. Previously, we showed that ecdysteroid signaling cell non-autonomously regulates early germline differentiation via its soma-specific co-activator and co-repressor, Taiman and Abrupt. Now, we demonstrate that this regulation is modulated by the miRNA let-7, which acts in a positive feedback loop to confer ecdysone signaling robustness via targeting its repressor, the transcription factor Abrupt. This feedback loop adjusts ecdysteroid signaling in response to some stressful alterations in the external and internal conditions, which include temperature stress and aging, but not nutritional deprivation. Upon let-7 deficit, escort cells fail to properly differentiate: their shape, division, and cell adhesive characteristics are perturbed. These cells have confused cellular identity and form columnar-like rather than squamous epithelium and fail to send protrusions in between differentiating germline cysts, affecting soma-germline communication. Particularly, levels of the homophilic cell adhesion protein Cadherin, which recruits Wg signaling transducer β-catenin, are increased in mutant escort cells and, correspondingly, in the adjacent germline cells. Readjustment of heterotypic (soma-germline) cell adhesion modulates Wg signaling intensity in the germline, which in turn regulates histone modifications that promote expression of the genes necessary to trigger early germline differentiation. Thus, our data first show the intrinsic role for Wg signaling in the germline and support a model where the soma influences the tempo of germline differentiation in response to external conditions.
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Affiliation(s)
- Annekatrin König
- Max Planck Research Group of Gene Expression and Signaling, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Halyna R Shcherbata
- Max Planck Research Group of Gene Expression and Signaling, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
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58
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Mukai M, Hira S, Nakamura K, Nakamura S, Kimura H, Sato M, Kobayashi S. H3K36 Trimethylation-Mediated Epigenetic Regulation is Activated by Bam and Promotes Germ Cell Differentiation During Early Oogenesis in Drosophila. Biol Open 2015; 4:119-24. [PMID: 25572421 PMCID: PMC4365480 DOI: 10.1242/bio.201410850] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Epigenetic silencing is critical for maintaining germline stem cells in Drosophila ovaries. However, it remains unclear how the differentiation factor, Bag-of-marbles (Bam), counteracts transcriptional silencing. We found that the trimethylation of lysine 36 on histone H3 (H3K36me3), a modification that is associated with gene activation, is enhanced in Bam-expressing cells. H3K36me3 levels were reduced in flies deficient in Bam. Inactivation of the Set2 methyltransferase, which confers the H3K36me3 modification, in germline cells markedly reduced H3K36me3 and impaired differentiation. Genetic analyses revealed that Set2 acts downstream of Bam. Furthermore, orb expression, which is required for germ cell differentiation, was activated by Set2, probably through direct H3K36me3 modification of the orb locus. Our data indicate that H3K36me3-mediated epigenetic regulation is activated by bam, and that this modification facilitates germ cell differentiation, probably through transcriptional activation. This work provides a novel link between Bam and epigenetic transcriptional control.
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Affiliation(s)
- Masanori Mukai
- Department of Biology, Faculty of Science and Engineering, Konan University, Okamoto, Higashinada, Kobe 658-8501, Japan Graduate School of Natural Science, Konan University, Okamoto, Higashinada, Kobe 658-8501, Japan Institute for Integrative Neurobiology, Konan University, Okamoto, Higashinada, Kobe 658-8501, Japan
| | - Seiji Hira
- Graduate School of Natural Science, Konan University, Okamoto, Higashinada, Kobe 658-8501, Japan Research Fellow of Japan Society for the Promotion of Science, Tokyo 102-0083, Japan
| | - Katsuhiro Nakamura
- Graduate School of Natural Science, Konan University, Okamoto, Higashinada, Kobe 658-8501, Japan
| | - Shoichi Nakamura
- Department of Biology, Faculty of Science and Engineering, Konan University, Okamoto, Higashinada, Kobe 658-8501, Japan
| | - Hiroshi Kimura
- Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
| | - Masanao Sato
- Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences, Higashiyama, Myodaiji, Okazaki 444-8787, Japan
| | - Satoru Kobayashi
- Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences, Higashiyama, Myodaiji, Okazaki 444-8787, Japan Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan
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59
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Stine RR, Greenspan LJ, Ramachandran KV, Matunis EL. Coordinate regulation of stem cell competition by Slit-Robo and JAK-STAT signaling in the Drosophila testis. PLoS Genet 2014; 10:e1004713. [PMID: 25375180 PMCID: PMC4222695 DOI: 10.1371/journal.pgen.1004713] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 08/26/2014] [Indexed: 02/01/2023] Open
Abstract
Stem cells in tissues reside in and receive signals from local microenvironments called niches. Understanding how multiple signals within niches integrate to control stem cell function is challenging. The Drosophila testis stem cell niche consists of somatic hub cells that maintain both germline stem cells and somatic cyst stem cells (CySCs). Here, we show a role for the axon guidance pathway Slit-Roundabout (Robo) in the testis niche. The ligand Slit is expressed specifically in hub cells while its receptor, Roundabout 2 (Robo2), is required in CySCs in order for them to compete for occupancy in the niche. CySCs also require the Slit-Robo effector Abelson tyrosine kinase (Abl) to prevent over-adhesion of CySCs to the niche, and CySCs mutant for Abl outcompete wild type CySCs for niche occupancy. Both Robo2 and Abl phenotypes can be rescued through modulation of adherens junction components, suggesting that the two work together to balance CySC adhesion levels. Interestingly, expression of Robo2 requires JAK-STAT signaling, an important maintenance pathway for both germline and cyst stem cells in the testis. Our work indicates that Slit-Robo signaling affects stem cell function downstream of the JAK-STAT pathway by controlling the ability of stem cells to compete for occupancy in their niche.
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Affiliation(s)
- Rachel R. Stine
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Leah J. Greenspan
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Kapil V. Ramachandran
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Erika L. Matunis
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
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60
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He J, Xuan T, Xin T, An H, Wang J, Zhao G, Li M. Evidence for chromatin-remodeling complex PBAP-controlled maintenance of the Drosophila ovarian germline stem cells. PLoS One 2014; 9:e103473. [PMID: 25068272 PMCID: PMC4113433 DOI: 10.1371/journal.pone.0103473] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 06/30/2014] [Indexed: 11/19/2022] Open
Abstract
In the Drosophila oogenesis, germline stem cells (GSCs) continuously self-renew and differentiate into daughter cells for consecutive germline lineage commitment. This developmental process has become an in vivo working platform for studying adult stem cell fate regulation. An increasing number of studies have shown that while concerted actions of extrinsic signals from the niche and intrinsic regulatory machineries control GSC self-renewal and germline differentiation, epigenetic regulation is implicated in the process. Here, we report that Brahma (Brm), the ATPase subunit of the Drosophila SWI/SNF chromatin-remodeling complexes, is required for maintaining GSC fate. Removal or knockdown of Brm function in either germline or niche cells causes a GSC loss, but does not disrupt normal germline differentiation within the germarium evidenced at the molecular and morphological levels. There are two Drosophila SWI/SNF complexes: the Brm-associated protein (BAP) complex and the polybromo-containing BAP (PBAP) complex. More genetic studies reveal that mutations in polybromo/bap180, rather than gene encoding Osa, the BAP complex-specific subunit, elicit a defect in GSC maintenance reminiscent of the brm mutant phenotype. Further genetic interaction test suggests a functional association between brm and polybromo in controlling GSC self-renewal. Taken together, studies in this paper provide the first demonstration that Brm in the form of the PBAP complex functions in the GSC fate regulation.
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Affiliation(s)
- Jie He
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
| | - Tao Xuan
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, P R China
- * E-mail: (TX); (ML)
| | - Tianchi Xin
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
| | - Hongbo An
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
| | - Jinye Wang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, P R China
| | - Gengchun Zhao
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
| | - Mingfa Li
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
- * E-mail: (TX); (ML)
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61
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Molla-Herman A, Matias NR, Huynh JR. Chromatin modifications regulate germ cell development and transgenerational information relay. CURRENT OPINION IN INSECT SCIENCE 2014; 1:10-18. [PMID: 32846502 DOI: 10.1016/j.cois.2014.04.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 04/23/2014] [Accepted: 04/23/2014] [Indexed: 06/11/2023]
Abstract
Germ cells transmit genetic, cytoplasmic and epigenetic information to the next generation. Recent reports describe the importance of chromatin modifiers and small RNAs for germ cells development in Drosophila. We also review exciting progress in our understanding of piRNAs functions, which demonstrate that this class of small RNAs is both an adaptive and inheritable epigenetic memory.
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Affiliation(s)
- Anahi Molla-Herman
- Department of Genetics and Developmental Biology, Institut Curie, Paris, France; CNRS UMR3215, Inserm U934, F-75248 Paris, France
| | - Neuza R Matias
- Department of Genetics and Developmental Biology, Institut Curie, Paris, France; CNRS UMR3215, Inserm U934, F-75248 Paris, France
| | - Jean-René Huynh
- Department of Genetics and Developmental Biology, Institut Curie, Paris, France; CNRS UMR3215, Inserm U934, F-75248 Paris, France.
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62
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A regulatory network of Drosophila germline stem cell self-renewal. Dev Cell 2014; 28:459-73. [PMID: 24576427 DOI: 10.1016/j.devcel.2014.01.020] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 11/24/2013] [Accepted: 01/22/2014] [Indexed: 12/24/2022]
Abstract
Stem cells possess the capacity to generate two cells of distinct fate upon division: one cell retaining stem cell identity and the other cell destined to differentiate. These cell fates are established by cell-type-specific genetic networks. To comprehensively identify components of these networks, we performed a large-scale RNAi screen in Drosophila female germline stem cells (GSCs) covering ∼25% of the genome. The screen identified 366 genes that affect GSC maintenance, differentiation, or other processes involved in oogenesis. Comparison of GSC regulators with neural stem cell self-renewal factors identifies common and cell-type-specific self-renewal genes. Importantly, we identify the histone methyltransferase Set1 as a GSC-specific self-renewal factor. Loss of Set1 in neural stem cells does not affect cell fate decisions, suggesting a differential requirement of H3K4me3 in different stem cell lineages. Altogether, our study provides a resource that will help to further dissect the networks underlying stem cell self-renewal.
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63
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Iovino N. Drosophila epigenome reorganization during oocyte differentiation and early embryogenesis. Brief Funct Genomics 2014; 13:246-53. [PMID: 24665128 DOI: 10.1093/bfgp/elu007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In sexually reproducing organisms, propagation of the species relies on specialized haploid cells (gametes) produced by germ cells. During their development in the adult germline, the female and male gametes undergo a complex differentiation process that requires transcriptional regulation and chromatin reorganization. After fertilization, the gametes then go through extensive epigenetic reprogramming, which resets the cells to a totipotent state essential for the development of the embryo. Several histone modifications characterize distinct developmental stages of gamete formation and early embryonic development, but it is unknown whether these modifications have any physiological role. Furthermore, accumulating evidence suggests that environmentally induced chromatin changes can be inherited, yet the mechanisms underlying zygotic inheritance of the gamete epigenome remain unclear. This review gives a brief overview of the mechanisms of transgenerational epigenetic inheritance and examines the function of epigenetics during oogenesis and early embryogenesis with a focus on histone posttranslational modifications.
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64
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Ma X, Wang S, Do T, Song X, Inaba M, Nishimoto Y, Liu LP, Gao Y, Mao Y, Li H, McDowell W, Park J, Malanowski K, Peak A, Perera A, Li H, Gaudenz K, Haug J, Yamashita Y, Lin H, Ni JQ, Xie T. Piwi is required in multiple cell types to control germline stem cell lineage development in the Drosophila ovary. PLoS One 2014; 9:e90267. [PMID: 24658126 PMCID: PMC3962343 DOI: 10.1371/journal.pone.0090267] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 01/27/2014] [Indexed: 12/12/2022] Open
Abstract
The piRNA pathway plays an important role in maintaining genome stability in the germ line by silencing transposable elements (TEs) from fly to mammals. As a highly conserved piRNA pathway component, Piwi is widely expressed in both germ cells and somatic cells in the Drosophila ovary and is required for piRNA production in both cell types. In addition to its known role in somatic cap cells to maintain germline stem cells (GSCs), this study has demonstrated that Piwi has novel functions in somatic cells and germ cells of the Drosophila ovary to promote germ cell differentiation. Piwi knockdown in escort cells causes a reduction in escort cell (EC) number and accumulation of undifferentiated germ cells, some of which show active BMP signaling, indicating that Piwi is required to maintain ECs and promote germ cell differentiation. Simultaneous knockdown of dpp, encoding a BMP, in ECs can partially rescue the germ cell differentiation defect, indicating that Piwi is required in ECs to repress dpp. Consistent with its key role in piRNA production, TE transcripts increase significantly and DNA damage is also elevated in the piwi knockdown somatic cells. Germ cell-specific knockdown of piwi surprisingly causes depletion of germ cells before adulthood, suggesting that Piwi might control primordial germ cell maintenance or GSC establishment. Finally, Piwi inactivation in the germ line of the adult ovary leads to gradual GSC loss and germ cell differentiation defects, indicating the intrinsic role of Piwi in adult GSC maintenance and differentiation. This study has revealed new germline requirement of Piwi in controlling GSC maintenance and lineage differentiation as well as its new somatic function in promoting germ cell differentiation. Therefore, Piwi is required in multiple cell types to control GSC lineage development in the Drosophila ovary.
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Affiliation(s)
- Xing Ma
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, Kansas, United States of America
| | - Su Wang
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, Kansas, United States of America
| | - Trieu Do
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Xiaoqing Song
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Mayu Inaba
- Life Sciences Institute, Center for Stem Cell Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Yoshiya Nishimoto
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Lu-ping Liu
- School of Medicine, Tsinghua University, Beijing, China
| | - Yuan Gao
- School of Medicine, Tsinghua University, Beijing, China
| | - Ying Mao
- School of Medicine, Tsinghua University, Beijing, China
| | - Hui Li
- School of Medicine, Tsinghua University, Beijing, China
| | - William McDowell
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Jungeun Park
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Kate Malanowski
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Allison Peak
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Anoja Perera
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Hua Li
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Karin Gaudenz
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Jeff Haug
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Yukiko Yamashita
- Life Sciences Institute, Center for Stem Cell Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Haifan Lin
- Yale Stem Cell Center, Yale University School of Medicine, New Haven, Connecticut, United Sates of America
| | - Jian-quan Ni
- School of Medicine, Tsinghua University, Beijing, China
| | - Ting Xie
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, Kansas, United States of America
- * E-mail:
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Hamada-Kawaguchi N, Nore BF, Kuwada Y, Smith CIE, Yamamoto D. Btk29A promotes Wnt4 signaling in the niche to terminate germ cell proliferation in Drosophila. Science 2014; 343:294-7. [PMID: 24436419 DOI: 10.1126/science.1244512] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Btk29A is the Drosophila ortholog of the mammalian Bruton's tyrosine kinase (Btk), mutations of which in humans cause a heritable immunodeficiency disease. Btk29A mutations stabilized the proliferating cystoblast fate, leading to an ovarian tumor. This phenotype was rescued by overexpression of wild-type Btk29A and phenocopied by the interference of Wnt4-β-catenin signaling or its putative downstream nuclear protein Piwi in somatic escort cells. Btk29A and mammalian Btk directly phosphorylated tyrosine residues of β-catenin, leading to the up-regulation of its transcriptional activity. Thus, we identify a transcriptional switch involving the kinase Btk29A/Btk and its phosphorylation target, β-catenin, which functions downstream of Wnt4 in escort cells to terminate Drosophila germ cell proliferation through up-regulation of piwi expression. This signaling mechanism likely represents a versatile developmental switch.
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Affiliation(s)
- Noriko Hamada-Kawaguchi
- Department of Developmental Biology and Neurosciences, Tohoku University Graduate School of Life Sciences, Sendai 980-8577, Japan
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66
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Clough E, Tedeschi T, Hazelrigg T. Epigenetic regulation of oogenesis and germ stem cell maintenance by the Drosophila histone methyltransferase Eggless/dSetDB1. Dev Biol 2014; 388:181-91. [PMID: 24485852 DOI: 10.1016/j.ydbio.2014.01.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Revised: 01/10/2014] [Accepted: 01/17/2014] [Indexed: 11/16/2022]
Abstract
The Drosophila melanogaster histone lysine methyltransferase (HKMT) Eggless (Egg/dSETDB1) catalyzes methylation of Histone H3 lysine 9 (H3K9), a signature of repressive heterochromatin. Our previous studies showed that H3K9 methylation by Egg is required for oogenesis. Here we analyze a set of EMS-induced mutations in the egg gene, identify the molecular lesions of these mutations, and compare the effects on oogenesis of both strong loss-of-function and weak hypomorphic alleles. These studies show that H3K9 methylation by Egg is required for multiple stages of oogenesis. Mosaic expression experiments show that the egg gene is not required intrinsically in the germ cells for their early differentiation, but is required in the germ cells for their survival past stage 5 of oogenesis. egg is also required in germ stem cells for their maintenance, since egg- germ stem cells initially survive but are not maintained as females age. Mosaic analysis also reveals that the early egg chamber budding defects in egg- ovaries are due to an intrinsic requirement for egg in follicle stem cells and their descendents, and that egg plays a non-autonomous role in somatic cells in the germarium to influence the differentiation of early germ cells.
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Affiliation(s)
- Emily Clough
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Thomas Tedeschi
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Tulle Hazelrigg
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
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Chorion formation in panoistic ovaries requires windei and trimethylation of histone 3 lysine 9. Exp Cell Res 2014; 320:46-53. [DOI: 10.1016/j.yexcr.2013.07.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 07/09/2013] [Accepted: 07/10/2013] [Indexed: 02/05/2023]
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Tarayrah L, Chen X. Epigenetic regulation in adult stem cells and cancers. Cell Biosci 2013; 3:41. [PMID: 24172544 PMCID: PMC3852361 DOI: 10.1186/2045-3701-3-41] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 09/05/2013] [Indexed: 12/23/2022] Open
Abstract
Adult stem cells maintain tissue homeostasis by their ability to both self-renew and differentiate to distinct cell types. Multiple signaling pathways have been shown to play essential roles as extrinsic cues in maintaining adult stem cell identity and activity. Recent studies also show dynamic regulation by epigenetic mechanisms as intrinsic factors in multiple adult stem cell lineages. Emerging evidence demonstrates intimate crosstalk between these two mechanisms. Misregulation of adult stem cell activity could lead to tumorigenesis, and it has been proposed that cancer stem cells may be responsible for tumor growth and metastasis. However, it is unclear whether cancer stem cells share commonalities with normal adult stem cells. In this review, we will focus on recent discoveries of epigenetic regulation in multiple adult stem cell lineages. We will also discuss how epigenetic mechanisms regulate cancer stem cell activity and probe the common and different features between cancer stem cells and normal adult stem cells.
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Affiliation(s)
- Lama Tarayrah
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
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69
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Xin T, Xuan T, Tan J, Li M, Zhao G, Li M. The Drosophila putative histone acetyltransferase Enok maintains female germline stem cells through regulating Bruno and the niche. Dev Biol 2013; 384:1-12. [PMID: 24120347 DOI: 10.1016/j.ydbio.2013.10.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/29/2013] [Accepted: 10/02/2013] [Indexed: 12/16/2022]
Abstract
Maintenance of adult stem cells is largely dependent on the balance between their self-renewal and differentiation. The Drosophila ovarian germline stem cells (GSCs) provide a powerful in vivo system for studying stem cell fate regulation. It has been shown that maintaining the GSC population involves both genetic and epigenetic mechanisms. Although the role of epigenetic regulation in this process is evident, the underlying mechanisms remain to be further explored. In this study, we find that Enoki mushroom (Enok), a Drosophila putative MYST family histone acetyltransferase controls GSC maintenance in the ovary at multiple levels. Removal or knockdown of Enok in the germline causes a GSC maintenance defect. Further studies show that the cell-autonomous role of Enok in maintaining GSCs is not dependent on the BMP/Bam pathway. Interestingly, molecular studies reveal an ectopic expression of Bruno, an RNA binding protein, in the GSCs and their differentiating daughter cells elicited by the germline Enok deficiency. Misexpression of Bruno in GSCs and their immediate descendants results in a GSC loss that can be exacerbated by incorporating one copy of enok mutant allele. These data suggest a role for Bruno in Enok-controlled GSC maintenance. In addition, we observe that Enok is required for maintaining GSCs non-autonomously. Compromised expression of enok in the niche cells impairs the niche maintenance and BMP signal output, thereby causing defective GSC maintenance. This is the first demonstration that the niche size control requires an epigenetic mechanism. Taken together, studies in this paper provide new insights into the GSC fate regulation.
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Affiliation(s)
- Tianchi Xin
- MoE Key Laboratory of Developmental Genetics and Neuropsychiatric Diseases, Bio-X Institutes, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240 Shanghai, PR China
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70
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Xuan T, Xin T, He J, Tan J, Gao Y, Feng S, He L, Zhao G, Li M. dBre1/dSet1-dependent pathway for histone H3K4 trimethylation has essential roles in controlling germline stem cell maintenance and germ cell differentiation in the Drosophila ovary. Dev Biol 2013; 379:167-81. [PMID: 23624310 DOI: 10.1016/j.ydbio.2013.04.015] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 03/27/2013] [Accepted: 04/13/2013] [Indexed: 11/28/2022]
Abstract
The Drosophila ovarian germline stem cells (GSCs) constantly experience self-renewal and differentiation, ensuring the female fertility throughout life. The balance between GSC self-renewal and differentiation is exquisitely regulated by the stem cell niche, the stem cells themselves and systemic factors. Increasing evidence has shown that the GSC regulation also involves epigenetic mechanisms including chromatin remodeling and histone modification. Here, we find that dBre1, an E3 ubiquitin ligase, functions in controlling GSC self-renewal and germ cell differentiation via distinct mechanisms. Removal or knock down of dBre1 function in the germline or somatic niche cell lineage leads to a gradual GSC loss and disruption of H3K4 trimethylation in the Drosophila ovary. Further studies suggest that the defective GSC maintenance is attributable to compromised BMP signaling emitted from the stem cell niche and impaired adhesion of GSCs to their niche. On the other hand, dBre1-RNAi expression in escort cells causes a loss of H3K4 trimethylation and accumulation of spectrosome-containing single germ cells in the germarium. Reducing dpp or dally levels suppresses the germ cell differentiation defects, indicating that dBre1 limits BMP signaling activities for the differentiation control. Strikingly, all phenotypes observed in dBre1 mutant ovaries can be mimicked by RNAi-based reduced expression of dSet1, a Drosophila H3K4 trimethylase. Moreover, genetic studies favor that dBre1 interacts with dSet1 in controlling GSC maintenance and germ cell differentiation. Taken together, we identify a dBre1/dSet1-dependent pathway for the H3K4 methylation involved in the cell fate regulation in the Drosophila ovary.
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Affiliation(s)
- Tao Xuan
- MoE Key Laboratory of Developmental Genetics and Neuropsychiatric Diseases, Bio-X Institutes, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240 Shanghai, PR China
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71
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The nucleus- and endoplasmic reticulum-targeted forms of protein tyrosine phosphatase 61F regulate Drosophila growth, life span, and fecundity. Mol Cell Biol 2013; 33:1345-56. [PMID: 23339871 DOI: 10.1128/mcb.01411-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The protein tyrosine phosphatases (PTPs) T cell PTP (TCPTP) and PTP1B share a high level of catalytic domain sequence and structural similarity yet display distinct differences in substrate recognition and function. Their noncatalytic domains contribute to substrate selectivity and function by regulating TCPTP nucleocytoplasmic shuttling and targeting PTP1B to the endoplasmic reticulum (ER). The Drosophila TCPTP/PTP1B orthologue PTP61F has two variants with identical catalytic domains that are differentially targeted to the ER and nucleus. Here we demonstrate that the PTP61F variants differ in their ability to negatively regulate insulin signaling in vivo, with the nucleus-localized form (PTP61Fn) being more effective than the ER-localized form (PTP61Fm). We report that PTP61Fm is reliant on the adaptor protein Dock to attenuate insulin signaling in vivo. Also, we show that the PTP61F variants differ in their capacities to regulate growth, with PTP61Fn but not PTP61Fm attenuating cellular proliferation. Furthermore, we generate a mutant lacking both PTP61F variants, which displays a reduction in median life span and a decrease in female fecundity, and show that both variants are required to rescue these mutant phenotypes. Our findings define the role of PTP61F in life span and fecundity and reinforce the importance of subcellular localization in mediating PTP function in vivo.
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Singh SR, Liu Y, Kango-Singh M, Nevo E. Genetic, immunofluorescence labeling, and in situ hybridization techniques in identification of stem cells in male and female germline niches. Methods Mol Biol 2013; 1035:9-23. [PMID: 23959978 DOI: 10.1007/978-1-62703-508-8_2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Stem cells have an enormous capacity of self-renewal, as well as the ability to differentiate into specialized cell types. Proper control of these two properties of stem cells is crucial for animal development, growth control, and reproduction. Germline stem cells (GSCs) are a self-renewing population of germ cells, which generate haploid gametes (sperms or oocyte) that transmit genetic information from generation to generation. In Drosophila testis and ovary, GSCs are anchored around the niche cells. The cap cells cluster in females and hub cells in males act as a niche to control GSC behavior. With highly sophisticated genetic techniques in Drosophila, tremendous progress has been made in understanding the interactions between stem cells and niches at cellular and molecular levels. Here, we provide details of genetic, immunofluorescence labeling, and in situ hybridization techniques in identification and characterization of stem cells in Drosophila male and female germline niches.
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Affiliation(s)
- Shree Ram Singh
- Mouse Cancer Genetics Program, National Cancer Institute, NIH, Frederick, MD, USA
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74
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Xie T. Control of germline stem cell self-renewal and differentiation in the Drosophila ovary: concerted actions of niche signals and intrinsic factors. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 2:261-73. [PMID: 24009036 DOI: 10.1002/wdev.60] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In the Drosophila ovary, germline stem cells (GSCs) physically interact with their niche composed of terminal filament cells, cap cells, and possibly GSC-contacting escort cells (ECs). A GSC divides to generate a self-renewing stem cell that remains in the niche and a differentiating daughter that moves away from the niche. The GSC niche provides a bone morphogenetic protein (BMP) signal that maintains GSC self-renewal by preventing stem cell differentiation via repression of the differentiation-promoting gene bag of marbles (bam). In addition, it expresses E-cadherin, which mediates cell adhesion for anchoring GSCs in the niche, enabling continuous self-renewal. GSCs themselves also express different classes of intrinsic factors, including signal transducers, transcription factors, chromatin remodeling factors, translation regulators, and miRNAs, which control self-renewal by strengthening interactions with the niche and repressing various differentiation pathways. Differentiated GSC daughters, known as cystoblasts (CBs), also express distinct classes of intrinsic factors to inhibit self-renewal and promote germ cell differentiation. Surprisingly, GSC progeny are also dependent on their surrounding ECs for proper differentiation at least partly by preventing BMP from diffusing to the differentiated germ cell zone and by repressing ectopic BMP expression. Therefore, both GSC self-renewal and CB differentiation are controlled by collaborative actions of extrinsic signals and intrinsic factors.
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Affiliation(s)
- Ting Xie
- Stowers Institute for Medical Research, Kansas City, MO, USA; Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, KS, USA.
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