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Aguilar GR, Vidal B, Ji H, Evenblij J, Liao CP, Ji H, Valperga G, Fang-Yen C, Hobert O. Functional analysis of conserved C. elegans bHLH family members uncovers lifespan control by a peptidergic hub neuron. PLoS Biol 2025; 23:e3002979. [PMID: 39761329 PMCID: PMC11703107 DOI: 10.1371/journal.pbio.3002979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2024] [Accepted: 12/11/2024] [Indexed: 01/15/2025] Open
Abstract
Throughout the animal kingdom, several members of the basic helix-loop-helix (bHLH) family act as proneural genes during early steps of nervous system development. Roles of bHLH genes in specifying terminal differentiation of postmitotic neurons have been less extensively studied. We analyze here the function of 5 Caenorhabditis elegans bHLH genes, falling into 3 phylogenetically conserved subfamilies, which are continuously expressed in a very small number of postmitotic neurons in the central nervous system. We show (a) that 2 orthologs of the vertebrate bHLHe22/e23 genes, called hlh-17 and hlh-32, function redundantly to specify the identity of a single head interneuron class (AUA), as well as an individual motor neuron (VB2); (b) that the PTF1a ortholog hlh-13 acts as a terminal selector to control terminal differentiation and function of the sole octopaminergic neuron class in C. elegans, RIC; and (c) that the NHLH1/2 ortholog hlh-15 controls terminal differentiation and function of the peptidergic AVK head interneuron class, a known neuropeptidergic signaling hub in the animal. Strikingly, through null mutant analysis and cell-specific rescue experiments, we find that loss of hlh-15/NHLH in the peptidergic AVK neurons and the resulting abrogation of neuropeptide secretion from these neurons causes a substantially extended lifespan of the animal, which we propose to be akin to hypothalamic control of lifespan in vertebrates. Our functional analysis reveals themes of bHLH gene function during terminal differentiation that are complementary to the earlier lineage specification roles of other bHLH family members. However, such late functions are much more sparsely employed by members of the bHLH transcription factor family, compared to the function of the much more broadly employed homeodomain transcription factor family.
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Affiliation(s)
- G. Robert Aguilar
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Berta Vidal
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Hongzhu Ji
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Joke Evenblij
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
- Technische Universität, Braunschweig, Germany
| | - Chien-Po Liao
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Hongfei Ji
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States of America
| | - Giulio Valperga
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Christopher Fang-Yen
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States of America
| | - Oliver Hobert
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
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Poole RJ, Flames N, Cochella L. Neurogenesis in Caenorhabditis elegans. Genetics 2024; 228:iyae116. [PMID: 39167071 PMCID: PMC11457946 DOI: 10.1093/genetics/iyae116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2024] [Accepted: 06/24/2024] [Indexed: 08/23/2024] Open
Abstract
Animals rely on their nervous systems to process sensory inputs, integrate these with internal signals, and produce behavioral outputs. This is enabled by the highly specialized morphologies and functions of neurons. Neuronal cells share multiple structural and physiological features, but they also come in a large diversity of types or classes that give the nervous system its broad range of functions and plasticity. This diversity, first recognized over a century ago, spurred classification efforts based on morphology, function, and molecular criteria. Caenorhabditis elegans, with its precisely mapped nervous system at the anatomical level, an extensive molecular description of most of its neurons, and its genetic amenability, has been a prime model for understanding how neurons develop and diversify at a mechanistic level. Here, we review the gene regulatory mechanisms driving neurogenesis and the diversification of neuron classes and subclasses in C. elegans. We discuss our current understanding of the specification of neuronal progenitors and their differentiation in terms of the transcription factors involved and ensuing changes in gene expression and chromatin landscape. The central theme that has emerged is that the identity of a neuron is defined by modules of gene batteries that are under control of parallel yet interconnected regulatory mechanisms. We focus on how, to achieve these terminal identities, cells integrate information along their developmental lineages. Moreover, we discuss how neurons are diversified postembryonically in a time-, genetic sex-, and activity-dependent manner. Finally, we discuss how the understanding of neuronal development can provide insights into the evolution of neuronal diversity.
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Affiliation(s)
- Richard J Poole
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Nuria Flames
- Developmental Neurobiology Unit, Instituto de Biomedicina de Valencia IBV-CSIC, Valencia 46012, Spain
| | - Luisa Cochella
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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3
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Aguilar GR, Vidal B, Ji H, Evenblij J, Ji H, Valperga G, Liao CP, Fang-Yen C, Hobert O. Functional analysis of conserved C. elegans bHLH family members uncovers lifespan control by a peptidergic hub neuron. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.12.603289. [PMID: 39071424 PMCID: PMC11275782 DOI: 10.1101/2024.07.12.603289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
Throughout the animal kingdom, several members of the basic helix-loop-helix (bHLH) family act as proneural genes during early steps of nervous system development. Roles of bHLH genes in specifying terminal differentiation of postmitotic neurons have been less extensively studied. We analyze here the function of five C. elegans bHLH genes, falling into three phylogenetically conserved subfamilies, which are continuously expressed in a very small number of postmitotic neurons in the central nervous system. We show (a) that two orthologs of the vertebrate bHLHb4/b5 genes, called hlh-17 and hlh-32, function redundantly to specify the identity of a single head interneuron (AUA), as well as an individual motor neuron (VB2), (b) that the PTF1a ortholog hlh-13 acts as a terminal selector to control terminal differentiation and function of the sole octopaminergic neuron class in C. elegans, RIC, and (c) that the NHLH1/2 ortholog hlh-15 controls terminal differentiation and function of the peptidergic AVK head interneuron class, a known neuropeptidergic signaling hub in the animal. Strikingly, through null mutant analysis and cell-specific rescue experiments, we find that loss of hlh-15/NHLH in the peptidergic AVK neurons and the resulting abrogation of neuropeptide secretion causes a substantially expanded lifespan of the animal, revealing an unanticipated impact of a central, peptidergic hub neuron in regulating lifespan, which we propose to be akin to hypothalamic control of lifespan in vertebrates. Taken together, our functional analysis reveals themes of bHLH gene function during terminal differentiation that are complementary to the earlier lineage specification roles of other bHLH family members. However, such late functions are much more sparsely employed by members of the bHLH transcription factor family, compared to the function of the much more broadly employed homeodomain transcription factor family.
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Affiliation(s)
- G. Robert Aguilar
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY
| | - Berta Vidal
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY
| | - Hongzhu Ji
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY
| | - Joke Evenblij
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY
- Technische Universität, Braunschweig, Germany
| | - Hongfei Ji
- Department of Biomedical Engineering, Ohio State University, Columbus, OH
| | - Giulio Valperga
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY
| | - Chien-Po Liao
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY
| | | | - Oliver Hobert
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY
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4
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Suzuki M, Takagi S. An analysis of semaphorin-mediated cellular interactions in the Caenorhabditis elegans epidermis using the IR-LEGO single-cell gene induction system. Dev Growth Differ 2024; 66:308-319. [PMID: 38761018 PMCID: PMC11457500 DOI: 10.1111/dgd.12925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2024] [Revised: 04/15/2024] [Accepted: 04/21/2024] [Indexed: 05/20/2024]
Abstract
One of the major functions of the semaphorin signaling system is the regulation of cell shape. In the nematode Caenorhabditis elegans, membrane-bound semaphorins SMP-1/2 (SMPs) regulate the morphology of epidermal cells via their receptor plexin, PLX-1. In the larval male tail of the SMP-PLX-1 signaling mutants, the border between two epidermal cells, R1.p and R2.p, is displaced anteriorly, resulting in the anterior displacement of the anterior-most ray, ray 1, in the adult male. To elucidate how the intercellular signaling mediated by SMPs regulates the position of the intercellular border, we performed mosaic gene expression analyses by using infrared laser-evoked gene operator (IR-LEGO). We show that PLX-1 expressed in R1.p and SMP-1 expressed in R2.p are required for the proper positioning of ray 1. The result suggests that SMP signaling promotes extension, rather than retraction, of R1.p. This is in contrast to a previous finding that SMPs mediate inhibition of cell extension of vulval precursor cells, another group of epidermal cells of C. elegans, indicating the context dependence of cell shape control via the semaphorin signaling system.
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Affiliation(s)
- Motoshi Suzuki
- Division of Biological Science, Graduate School of ScienceNagoya UniversityNagoyaJapan
| | - Shin Takagi
- Division of Biological Science, Graduate School of ScienceNagoya UniversityNagoyaJapan
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Masoudi N, Schnabel R, Yemini E, Leyva-Díaz E, Hobert O. Cell-specific effects of the sole C. elegans Daughterless/E protein homolog, HLH-2, on nervous system development. Development 2023; 150:286219. [PMID: 36595352 PMCID: PMC10108603 DOI: 10.1242/dev.201366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 11/30/2022] [Indexed: 01/04/2023]
Abstract
Are there common mechanisms of neurogenesis used throughout an entire nervous system? We explored to what extent canonical proneural class I/II bHLH complexes are responsible for neurogenesis throughout the entire Caenorhabditis elegans nervous system. Distinct, lineage-specific proneural class II bHLH factors are generally thought to operate via interaction with a common, class I bHLH subunit, encoded by Daughterless in flies, the E proteins in vertebrates and HLH-2 in C. elegans. To eliminate function of all proneuronal class I/II bHLH complexes, we therefore genetically removed maternal and zygotic hlh-2 gene activity. We observed broad effects on neurogenesis, but still detected normal neurogenesis in many distinct neuron-producing lineages of the central and peripheral nervous system. Moreover, we found that hlh-2 selectively affects some aspects of neuron differentiation while leaving others unaffected. Although our studies confirm the function of proneuronal class I/II bHLH complexes in many different lineages throughout a nervous system, we conclude that their function is not universal, but rather restricted by lineage, cell type and components of differentiation programs affected.
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Affiliation(s)
- Neda Masoudi
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, NY 10027, USA
| | - Ralf Schnabel
- Institute of Genetics, Technische Universität Braunschweig, 38106 Braunschweig, Germany
| | - Eviatar Yemini
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, NY 10027, USA.,University of Massachusetts, Department of Neurobiology, Worcester, MA 1605-2324, USA
| | - Eduardo Leyva-Díaz
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, NY 10027, USA
| | - Oliver Hobert
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, NY 10027, USA
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6
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Filippopoulou K, Couillault C, Bertrand V. Multiple neural bHLHs ensure the precision of a neuronal specification event in Caenorhabditis elegans. Biol Open 2021; 10:273578. [PMID: 34854469 PMCID: PMC8713986 DOI: 10.1242/bio.058976] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 11/22/2021] [Indexed: 11/24/2022] Open
Abstract
Neural bHLH transcription factors play a key role in the early steps of neuronal specification in many animals. We have previously observed that the Achaete-Scute HLH-3, the Olig HLH-16 and their binding partner the E-protein HLH-2 activate the terminal differentiation program of a specific class of cholinergic neurons, AIY, in Caenorhabditis elegans. Here we identify a role for a fourth bHLH, the Neurogenin NGN-1, in this process, raising the question of why so many neural bHLHs are required for a single neuronal specification event. Using quantitative imaging we show that the combined action of different bHLHs is needed to activate the correct level of expression of the terminal selector transcription factors TTX-3 and CEH-10 that subsequently initiate and maintain the expression of a large battery of terminal differentiation genes. Surprisingly, the different bHLHs have an antagonistic effect on another target, the proapoptotic BH3-only factor EGL-1, normally not expressed in AIY and otherwise detrimental for its specification. We propose that the use of multiple neural bHLHs allows robust neuronal specification while, at the same time, preventing spurious activation of deleterious genes. Summary: During neuronal specification, the combined action of several neural bHLHs ensures the robust activation of terminal selector transcription factor expression and prevents the activation of deleterious genes.
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Affiliation(s)
| | - Carole Couillault
- Aix Marseille Univ, CNRS, IBDM, Turing Center for Living Systems, Marseille 13009, France
| | - Vincent Bertrand
- Aix Marseille Univ, CNRS, IBDM, Turing Center for Living Systems, Marseille 13009, France
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Masoudi N, Yemini E, Schnabel R, Hobert O. Piecemeal regulation of convergent neuronal lineages by bHLH transcription factors in Caenorhabditis elegans. Development 2021; 148:dev199224. [PMID: 34100067 PMCID: PMC8217713 DOI: 10.1242/dev.199224] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Accepted: 04/29/2021] [Indexed: 11/20/2022]
Abstract
Cells of the same type can be generated by distinct cellular lineages that originate in different parts of the developing embryo ('lineage convergence'). Several Caenorhabditis elegans neuron classes composed of left/right or radially symmetric class members display such lineage convergence. We show here that the C. elegans Atonal homolog lin-32 is differentially expressed in neuronal lineages that give rise to left/right or radially symmetric class members. Loss of lin-32 results in the selective loss of the expression of pan-neuronal markers and terminal selector-type transcription factors that confer neuron class-specific features. Another basic helix-loop-helix (bHLH) gene, the Achaete-Scute homolog hlh-14, is expressed in a mirror image pattern relative to lin-32 and is required to induce neuronal identity and terminal selector expression on the contralateral side of the animal. These findings demonstrate that distinct lineage histories converge via different bHLH factors at the level of induction of terminal selector identity determinants, which thus serve as integrators of distinct lineage histories. We also describe neuron-to-neuron identity transformations in lin-32 mutants, which we propose to also be the result of misregulation of terminal selector gene expression.
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Affiliation(s)
- Neda Masoudi
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, NY 10027, USA
| | - Eviatar Yemini
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, NY 10027, USA
| | - Ralf Schnabel
- Institute of Genetics, Technische Universität Braunschweig, 38106 Braunschweig, Germany
| | - Oliver Hobert
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, NY 10027, USA
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Zhou L, Ma X, Zhu N, Zou Q, Guo K, Bai L, Yu H, Hu J. The role of mab-3 in spermatogenesis and ontogenesis of pinewood nematode, Bursaphelenchus xylophilus. PEST MANAGEMENT SCIENCE 2021; 77:138-147. [PMID: 32652887 DOI: 10.1002/ps.6001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Revised: 06/21/2020] [Accepted: 07/11/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND Bursaphelenchus xylophilus is one of the most destructive invasive species, causing extensive economic losses worldwide. The sex ratio of female to male of B. xylophilus plays an important role in the nematode infestation. However, little is known about the processes of its sex determination. The double sex/mab-3-related family of transcription factors are highly conserved in animals, playing crucial roles in sex determination, spermatogenesis and ontogenesis. We therefore investigated its orthologue, Bxy-mab-3, in B. xylophilus. RESULTS Bxy-mab-3 has two typical conserved DNA-binding domains. It was observed in J2 (the second-stage of juveniles), J3, J4 and male adults (specifically on the spicules), but not in eggs or female adults via mRNA in situ hybridization. RNA-Seq indicated significantly higher expression in males. RNAi showed that the body size and sperm size of male adults were markedly smaller than those of the controls. Meanwhile, almost all the RNAi-treated males failed to mate with the normal females, even 26.34% of interfered males did not produce sperm. However, RNAi of Bxy-mab-3 had no effect on the sex ratio of B. xylophilus. CONCLUSION Bxy-mab-3 is indispensable for spermatogenesis, ontogenesis and mating behavior. It is a typical sex-determination gene with differential expression in males and females. However, knocking down Bxy-mab-3 expression could not alter the sex ratio as seen in other species. Our findings contribute towards a better understanding of the molecular events of Bxy-mab-3 in B. xylophilus, which provides promising hints for control of pine wilt disease by blocking ontogenesis and decreasing nematode fecundity.
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Affiliation(s)
- Lifeng Zhou
- State Key Laboratory of Subtropical Silviculture, College of Forestry and Biotechnology, Zhejiang Agricultural & Forestry University, Hangzhou, China
| | - Xinxin Ma
- State Key Laboratory of Subtropical Silviculture, College of Forestry and Biotechnology, Zhejiang Agricultural & Forestry University, Hangzhou, China
| | - Najie Zhu
- State Key Laboratory of Subtropical Silviculture, College of Forestry and Biotechnology, Zhejiang Agricultural & Forestry University, Hangzhou, China
| | - Qingchi Zou
- Natural Forest Protection Center, Liaoning Forestry and Grassland Bureau, Shenyang, China
| | - Kai Guo
- State Key Laboratory of Subtropical Silviculture, College of Forestry and Biotechnology, Zhejiang Agricultural & Forestry University, Hangzhou, China
| | - Liqun Bai
- State Key Laboratory of Subtropical Silviculture, College of Forestry and Biotechnology, Zhejiang Agricultural & Forestry University, Hangzhou, China
| | - Hongshi Yu
- State Key Laboratory of Subtropical Silviculture, College of Forestry and Biotechnology, Zhejiang Agricultural & Forestry University, Hangzhou, China
- School of BioSciences, The University of Melbourne, Parkville, VIC, Australia
| | - Jiafu Hu
- State Key Laboratory of Subtropical Silviculture, College of Forestry and Biotechnology, Zhejiang Agricultural & Forestry University, Hangzhou, China
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Lee J, Taylor CA, Barnes KM, Shen A, Stewart EV, Chen A, Xiang YK, Bao Z, Shen K. A Myt1 family transcription factor defines neuronal fate by repressing non-neuronal genes. eLife 2019; 8:e46703. [PMID: 31386623 PMCID: PMC6684318 DOI: 10.7554/elife.46703] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Accepted: 06/20/2019] [Indexed: 12/15/2022] Open
Abstract
Cellular differentiation requires both activation of target cell transcriptional programs and repression of non-target cell programs. The Myt1 family of zinc finger transcription factors contributes to fibroblast to neuron reprogramming in vitro. Here, we show that ztf-11 (Zinc-finger Transcription Factor-11), the sole Caenorhabditis elegans Myt1 homolog, is required for neurogenesis in multiple neuronal lineages from previously differentiated epithelial cells, including a neuron generated by a developmental epithelial-to-neuronal transdifferentiation event. ztf-11 is exclusively expressed in all neuronal precursors with remarkable specificity at single-cell resolution. Loss of ztf-11 leads to upregulation of non-neuronal genes and reduced neurogenesis. Ectopic expression of ztf-11 in epidermal lineages is sufficient to produce additional neurons. ZTF-11 functions together with the MuvB corepressor complex to suppress the activation of non-neuronal genes in neurons. These results dovetail with the ability of Myt1l (Myt1-like) to drive neuronal transdifferentiation in vitro in vertebrate systems. Together, we identified an evolutionarily conserved mechanism to specify neuronal cell fate by repressing non-neuronal genes.
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Affiliation(s)
- Joo Lee
- Department of BiochemistryStanford UniversityStanfordUnited States
- Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Caitlin A Taylor
- Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
- Department of BiologyStanford UniversityStanfordUnited States
| | | | - Ao Shen
- Department of PharmacologyUniversity of California, DavisDavisUnited States
| | | | - Allison Chen
- Developmental Biology ProgramSloan-Kettering InstituteNew YorkUnited States
| | - Yang K Xiang
- Department of PharmacologyUniversity of California, DavisDavisUnited States
| | - Zhirong Bao
- Developmental Biology ProgramSloan-Kettering InstituteNew YorkUnited States
| | - Kang Shen
- Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
- Department of BiologyStanford UniversityStanfordUnited States
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Effects of diethylcarbamazine and ivermectin treatment on Brugia malayi gene expression in infected gerbils ( Meriones unguiculatus). ACTA ACUST UNITED AC 2019; 5. [PMID: 33777408 PMCID: PMC7994942 DOI: 10.1017/pao.2019.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Lymphatic filariasis (LF) threatens nearly 20% of the world’s population and has handicapped one-third of the 120 million people currently infected. Current control and elimination programs for LF rely on mass drug administration of albendazole plus diethylcarbamazine (DEC) or ivermectin. Only the mechanism of action of albendazole is well understood. To gain a better insight into antifilarial drug action in vivo, we treated gerbils harbouring patent Brugia malayi infections with 6 mg kg−1 DEC, 0.15 mg kg−1 ivermectin or 1 mg kg−1 albendazole. Treatments had no effect on the numbers of worms present in the peritoneal cavity of treated animals, so effects on gene expression were a direct result of the drug and not complicated by dying parasites. Adults and microfilariae were collected 1 and 7 days post-treatment and RNA isolated for transcriptomic analysis. The experiment was repeated three times. Ivermectin treatment produced the most differentially expressed genes (DEGs), 113. DEC treatment yielded 61 DEGs. Albendazole treatment resulted in little change in gene expression, with only 6 genes affected. In total, nearly 200 DEGs were identified with little overlap between treatment groups, suggesting that these drugs may interfere in different ways with processes important for parasite survival, development, and reproduction.
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11
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Haag ES, Fitch DHA, Delattre M. From "the Worm" to "the Worms" and Back Again: The Evolutionary Developmental Biology of Nematodes. Genetics 2018; 210:397-433. [PMID: 30287515 PMCID: PMC6216592 DOI: 10.1534/genetics.118.300243] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 08/03/2018] [Indexed: 12/13/2022] Open
Abstract
Since the earliest days of research on nematodes, scientists have noted the developmental and morphological variation that exists within and between species. As various cellular and developmental processes were revealed through intense focus on Caenorhabditis elegans, these comparative studies have expanded. Within the genus Caenorhabditis, they include characterization of intraspecific polymorphisms and comparisons of distinct species, all generally amenable to the same laboratory culture methods and supported by robust genomic and experimental tools. The C. elegans paradigm has also motivated studies with more distantly related nematodes and animals. Combined with improved phylogenies, this work has led to important insights about the evolution of nematode development. First, while many aspects of C. elegans development are representative of Caenorhabditis, and of terrestrial nematodes more generally, others vary in ways both obvious and cryptic. Second, the system has revealed several clear examples of developmental flexibility in achieving a particular trait. This includes developmental system drift, in which the developmental control of homologous traits has diverged in different lineages, and cases of convergent evolution. Overall, the wealth of information and experimental techniques developed in C. elegans is being leveraged to make nematodes a powerful system for evolutionary cellular and developmental biology.
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Affiliation(s)
- Eric S Haag
- Department of Biology, University of Maryland, College Park, Maryland 20742
| | | | - Marie Delattre
- Laboratoire de Biologie Moléculaire de la Cellule, CNRS, INSERM, Ecole Normale Supérieure de Lyon, 69007, France
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12
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Unconventional function of an Achaete-Scute homolog as a terminal selector of nociceptive neuron identity. PLoS Biol 2018; 16:e2004979. [PMID: 29672507 PMCID: PMC5908064 DOI: 10.1371/journal.pbio.2004979] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 03/12/2018] [Indexed: 11/19/2022] Open
Abstract
Proneural genes are among the most early-acting genes in nervous system development, instructing blast cells to commit to a neuronal fate. Drosophila Atonal and Achaete-Scute complex (AS-C) genes, as well as their vertebrate orthologs, are basic helix-loop-helix (bHLH) transcription factors with such proneural activity. We show here that a C. elegans AS-C homolog, hlh-4, functions in a fundamentally different manner. In the embryonic, larval, and adult nervous systems, hlh-4 is expressed exclusively in a single nociceptive neuron class, ADL, and its expression in ADL is maintained via transcriptional autoregulation throughout the life of the animal. However, in hlh-4 null mutants, the ADL neuron is generated and still appears neuronal in overall morphology and expression of panneuronal and pansensory features. Rather than acting as a proneural gene, we find that hlh-4 is required for the ADL neuron to function properly, to adopt its correct morphology, to express its unusually large repertoire of olfactory receptor-encoding genes, and to express other known features of terminal ADL identity, including neurotransmitter phenotype, neuropeptides, ion channels, and electrical synapse proteins. hlh-4 is sufficient to induce ADL identity features upon ectopic expression in other neuron types. The expression of ADL terminal identity features is directly controlled by HLH-4 via a phylogenetically conserved E-box motif, which, through bioinformatic analysis, we find to constitute a predictive feature of ADL-expressed terminal identity markers. The lineage that produces the ADL neuron was previously shown to require the conventional, transient proneural activity of another AS-C homolog, hlh-14, demonstrating sequential activities of distinct AS-C-type bHLH genes in neuronal specification. Taken together, we have defined here an unconventional function of an AS-C-type bHLH gene as a terminal selector of neuronal identity and we speculate that such function could be reflective of an ancestral function of an "ur-" bHLH gene.
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Barr MM, García LR, Portman DS. Sexual Dimorphism and Sex Differences in Caenorhabditis elegans Neuronal Development and Behavior. Genetics 2018; 208:909-935. [PMID: 29487147 PMCID: PMC5844341 DOI: 10.1534/genetics.117.300294] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 01/05/2018] [Indexed: 01/05/2023] Open
Abstract
As fundamental features of nearly all animal species, sexual dimorphisms and sex differences have particular relevance for the development and function of the nervous system. The unique advantages of the nematode Caenorhabditis elegans have allowed the neurobiology of sex to be studied at unprecedented scale, linking ultrastructure, molecular genetics, cell biology, development, neural circuit function, and behavior. Sex differences in the C. elegans nervous system encompass prominent anatomical dimorphisms as well as differences in physiology and connectivity. The influence of sex on behavior is just as diverse, with biological sex programming innate sex-specific behaviors and modifying many other aspects of neural circuit function. The study of these differences has provided important insights into mechanisms of neurogenesis, cell fate specification, and differentiation; synaptogenesis and connectivity; principles of circuit function, plasticity, and behavior; social communication; and many other areas of modern neurobiology.
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Affiliation(s)
- Maureen M Barr
- Department of Genetics, Rutgers University, Piscataway, New Jersey 08854-8082
| | - L Rene García
- Department of Biology, Texas A&M University, College Station, Texas 77843-3258
| | - Douglas S Portman
- Department of Biomedical Genetics, University of Rochester, New York 14642
- Department of Neuroscience, University of Rochester, New York 14642
- Department of Biology, University of Rochester, New York 14642
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14
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Doitsidou M, Minevich G, Kroll JR, Soete G, Gowtham S, Korswagen HC, Sebastiaan van Zon J, Hobert O. A Caenorhabditis elegans Zinc Finger Transcription Factor, ztf-6, Required for the Specification of a Dopamine Neuron-Producing Lineage. G3 (BETHESDA, MD.) 2018; 8:17-26. [PMID: 29301976 PMCID: PMC5765345 DOI: 10.1534/g3.117.300132] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 10/31/2017] [Indexed: 12/12/2022]
Abstract
Invertebrate and vertebrate nervous systems generate different types of dopaminergic neurons in distinct parts of the brain. We have taken a genetic approach to understand how the four functionally related, but lineally unrelated, classes of dopaminergic neurons of the nematode Caenorhabditis elegans, located in distinct parts of its nervous system, are specified. We have identified several genes involved in the generation of a specific dopaminergic neuron type that is generated from the so-called postdeirid lineage, called PDE. Apart from classic proneural genes and components of the mediator complex, we identified a novel, previously uncharacterized zinc finger transcription factor, ztf-6 Loss of ztf-6 has distinct effects in different dopamine neuron-producing neuronal lineages. In the postdeirid lineage, ztf-6 is required for proper cell division patterns and the proper distribution of a critical cell fate determinant, the POP-1/TCF-like transcription factor.
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Affiliation(s)
- Maria Doitsidou
- Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center New York, NY 10032
- Centre for Discovery Brain Sciences, University of Edinburgh, EH8 9XD, UK
| | - Gregory Minevich
- Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center New York, NY 10032
| | - Jason R Kroll
- AMOLF, Amsterdam, 1098 XG, The Netherlands, 3584 CT Utrecht, The Netherlands
| | - Gwen Soete
- Hubrecht Institute, 3584 CT Utrecht, The Netherlands
| | - Sriharsh Gowtham
- Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center New York, NY 10032
| | | | | | - Oliver Hobert
- Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center New York, NY 10032
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY 10027
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15
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Rojo Romanos T, Pladevall-Morera D, Langebeck-Jensen K, Hansen S, Ng L, Pocock R. LIN-32/Atonal Controls Oxygen Sensing Neuron Development in Caenorhabditis elegans. Sci Rep 2017; 7:7294. [PMID: 28779171 PMCID: PMC5544745 DOI: 10.1038/s41598-017-07876-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 06/30/2017] [Indexed: 12/12/2022] Open
Abstract
Development of complex nervous systems requires precisely controlled neurogenesis. The generation and specification of neurons occur through the transcriptional and post-transcriptional control of complex regulatory networks. In vertebrates and invertebrates, the proneural basic-helix-loop-helix (bHLH) family of transcription factors has multiple functions in neurogenesis. Here, we identified the LIN-32/Atonal bHLH transcription factor as a key regulator of URXL/R oxygen-sensing neuron development in Caenorhabditis elegans. When LIN-32/Atonal expression is lost, the expression of URX specification and terminal differentiation genes is abrogated. As such, lin-32 mutant animals are unable to respond to increases in environmental oxygen. The URX neurons are generated from a branch of the cell lineage that also produces the CEPDL/R and URADL/R neurons. We found development of these neurons is also defective, suggesting that LIN-32/Atonal regulates neuronal development of the entire lineage. Finally, our results show that aspects of URX neuronal fate are partially restored in lin-32 mutant animals when the apoptosis pathway is inhibited. This suggests that, as in other organisms, LIN-32/Atonal regulates neuronal apoptosis.
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Affiliation(s)
- Teresa Rojo Romanos
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, 3800, Australia.,Biotech Research and Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, Denmark
| | - David Pladevall-Morera
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, 3800, Australia.,Biotech Research and Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, Denmark
| | - Kasper Langebeck-Jensen
- Biotech Research and Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, Denmark
| | - Stine Hansen
- Biotech Research and Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, Denmark
| | - Leelee Ng
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, 3800, Australia
| | - Roger Pocock
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, 3800, Australia. .,Biotech Research and Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, Denmark.
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16
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Serrano-Saiz E, Pereira L, Gendrel M, Aghayeva U, Bhattacharya A, Howell K, Garcia LR, Hobert O. A Neurotransmitter Atlas of the Caenorhabditis elegans Male Nervous System Reveals Sexually Dimorphic Neurotransmitter Usage. Genetics 2017; 206:1251-1269. [PMID: 28684604 PMCID: PMC5500128 DOI: 10.1534/genetics.117.202127] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 05/03/2017] [Indexed: 11/18/2022] Open
Abstract
The nervous system of most animals is sexually dimorphic but such dimorphisms are generally poorly mapped on an anatomical, cellular, and molecular level. The adult nervous system of the nematode Caenorhabditis elegans displays a number of clearly defined anatomical sexual dimorphisms, but molecular features of sexually dimorphic neurons remain sparse. In this resource paper, we provide a comprehensive atlas of neurotransmitters used in the nervous system of the male and compare it to that of the hermaphrodite. Among the three major neurotransmitter systems, acetylcholine (ACh) is the most frequently used, followed by glutamate (Glu), and lastly γ-aminobutyric acid (GABA). Many male-specific neurons utilize multiple neurotransmitter systems. Interestingly, we find that neurons that are present in both sexes alter their neurotransmitter usage depending on the sex of the animal. One neuron scales up its usage of ACh, another becomes serotonergic in males, and another one adds a new neurotransmitter (glutamate) to its nonsex-specific transmitter (ACh). In all these cases, neurotransmitter changes are correlated with substantial changes in synaptic connectivity. We assembled the neurotransmitter maps of the male-specific nervous system into a comprehensive atlas that describes the anatomical position of all the neurons of the male-specific nervous system relative to the sex-shared nervous system. We exemplify the usefulness of the neurotransmitter atlas by using it as a tool to define the expression pattern of a synaptic organizer molecule in the male tail. Taken together, the male neurotransmitter atlas provides an entry point for future functional and developmental analysis of the male nervous system.
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Affiliation(s)
- Esther Serrano-Saiz
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York 10027
| | - Laura Pereira
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York 10027
| | - Marie Gendrel
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York 10027
| | - Ulkar Aghayeva
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York 10027
| | - Abhishek Bhattacharya
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York 10027
| | - Kelly Howell
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York 10027
| | - L Rene Garcia
- Department of Biology, Texas A&M University, College Station, Texas 77843
| | - Oliver Hobert
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York 10027
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17
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Sallee MD, Littleford HE, Greenwald I. A bHLH Code for Sexually Dimorphic Form and Function of the C. elegans Somatic Gonad. Curr Biol 2017; 27:1853-1860.e5. [PMID: 28602651 DOI: 10.1016/j.cub.2017.05.059] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 05/05/2017] [Accepted: 05/17/2017] [Indexed: 10/19/2022]
Abstract
How sexually dimorphic gonads are generated is a fundamental question at the interface of developmental and evolutionary biology [1-3]. In C. elegans, sexual dimorphism in gonad form and function largely originates in different apportionment of roles to three regulatory cells of the somatic gonad primordium in young larvae. Their essential roles include leading gonad arm outgrowth, serving as the germline niche, connecting to epithelial openings, and organizing reproductive organ development. The development and function of the regulatory cells in both sexes requires the basic-helix-loop-helix (bHLH) transcription factor HLH-2, the sole ortholog of the E proteins mammalian E2A and Drosophila Daughterless [4-8], yet how they adopt different fates to execute their different roles has been unknown. Here, we show that each regulatory cell expresses a distinct complement of bHLH-encoding genes-and therefore distinct HLH-2:bHLH dimers-and formulate a "bHLH code" hypothesis for regulatory cell identity. We support this hypothesis by showing that the bHLH gene complement is both necessary and sufficient to confer particular regulatory cell fates. Strikingly, prospective regulatory cells can be directly reprogrammed into other regulatory cell types simply by loss or ectopic expression of bHLH genes, and male-to-female and female-to-male transformations indicate that the code is instructive for sexual dimorphism. The bHLH code appears to be embedded in a bow-tie regulatory architecture [9, 10], wherein sexual, positional, temporal, and lineage inputs connect through bHLH genes to diverse outputs for terminal features and provides a plausible mechanism for the evolutionary plasticity of gonad form seen in nematodes [11-15].
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Affiliation(s)
- Maria D Sallee
- Department of Genetics and Development, Columbia University, New York, NY 10027, USA; Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
| | - Hana E Littleford
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Iva Greenwald
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA; Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
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18
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Cell-Autonomous and Non-Cell-Autonomous Regulation of a Feeding State-Dependent Chemoreceptor Gene via MEF-2 and bHLH Transcription Factors. PLoS Genet 2016; 12:e1006237. [PMID: 27487365 PMCID: PMC4972359 DOI: 10.1371/journal.pgen.1006237] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 07/12/2016] [Indexed: 01/01/2023] Open
Abstract
Food and feeding-state dependent changes in chemoreceptor gene expression may allow Caenorhabditis elegans to modify their chemosensory behavior, but the mechanisms essential for these expression changes remain poorly characterized. We had previously shown that expression of a feeding state-dependent chemoreceptor gene, srh-234, in the ADL sensory neuron of C. elegans is regulated via the MEF-2 transcription factor. Here, we show that MEF-2 acts together with basic helix-loop-helix (bHLH) transcription factors to regulate srh-234 expression as a function of feeding state. We identify a cis-regulatory MEF2 binding site that is necessary and sufficient for the starvation-induced down regulation of srh-234 expression, while an E-box site known to bind bHLH factors is required to drive srh-234 expression in ADL. We show that HLH-2 (E/Daughterless), HLH-3 and HLH-4 (Achaete-scute homologs) act in ADL neurons to regulate srh-234 expression. We further demonstrate that the expression levels of srh-234 in ADL neurons are regulated remotely by MXL-3 (Max-like 3 homolog) and HLH-30 (TFEB ortholog) acting in the intestine, which is dependent on insulin signaling functioning specifically in ADL neurons. We also show that this intestine-to-neuron feeding-state regulation of srh-234 involves a subset of insulin-like peptides. These results combined suggest that chemoreceptor gene expression is regulated by both cell-autonomous and non-cell-autonomous transcriptional mechanisms mediated by MEF2 and bHLH factors, which may allow animals to fine-tune their chemosensory responses in response to changes in their feeding state. Plasticity in chemoreceptor gene expression may be a simple strategy by which an animal can modulate its chemosensory responses in changing external and internal state conditions. However, the transcriptional mechanisms required for these chemoreceptor gene expression changes are poorly understood. Here, we describe the identification of a transcriptional module(s) consisting of MEF-2 and basic helix-loop-helix (bHLH) transcription factors and their cognate binding sites in Caenorhabditis elegans that act together in ADL sensory neurons to properly regulate expression of a feeding-state dependent chemoreceptor gene. We also showed that chemoreceptor gene expression in ADL neurons are regulated remotely by bHLH factors acting in the intestine through an insulin-mediated signaling pathway, implying a sensory neuron-gut interaction for modulating chemoreceptor gene expression as a function of feeding state. This work describes transcriptional mechanisms mediated by MEF-2 and bHLH factors by which the expression of individual chemoreceptor genes in C. elegans are changed in response to changes in feeding state conditions.
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19
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Kroetz MB, Zarkower D. Cell-Specific mRNA Profiling of the Caenorhabditis elegans Somatic Gonadal Precursor Cells Identifies Suites of Sex-Biased and Gonad-Enriched Transcripts. G3 (BETHESDA, MD.) 2015; 5:2831-41. [PMID: 26497144 PMCID: PMC4683654 DOI: 10.1534/g3.115.022517] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 10/16/2015] [Indexed: 02/07/2023]
Abstract
The Caenorhabditis elegans somatic gonad differs greatly between the two sexes in its pattern of cell divisions, migration, and differentiation. Despite decades of study, the genetic pathways directing early gonadal development and establishing sexual dimorphism in the gonad remain largely unknown. To help define the genetic networks that regulate gonadal development, we employed cell-specific RNA-seq. We identified transcripts present in the somatic gonadal precursor cells and their daughter cells of each sex at the onset of sexual differentiation. We identified several hundred gonad-enriched transcripts, including the majority of known regulators of early gonadal development, and transgenic reporter analysis confirmed the effectiveness of this approach. Before the division of the somatic gonad precursors, few sex-biased gonadal transcripts were detectable; less than 6 hr later, after their division, we identified more than 250 sex-biased transcripts, of which about a third were enriched in the somatic gonad compared to the whole animal. This indicates that a robust sex-biased developmental program, some of it gonad-specific, initiates in the somatic gonadal precursor cells around the time of their first division. About 10% of male-biased transcripts had orthologs with male-biased expression in the early mouse gonad, suggesting possible conservation of gonad sex differentiation. Cell-specific analysis also identified approximately 70 previously unannotated mRNA isoforms that are enriched in the somatic gonad. Our data illustrate the power of cell-specific transcriptome analysis and suggest that early sex differentiation in the gonad is controlled by a relatively small suite of differentially expressed genes, even after dimorphism has become apparent.
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Affiliation(s)
- Mary B Kroetz
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455
| | - David Zarkower
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455 Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455
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20
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Abstract
In this study, Sallee et al. demonstrate that E-protein dimer formation can promote C. elegans and human bHLH protein instability. By investigating HLH-2, the sole C. elegans E protein, the authors show that HLH-2 functions as a homodimer for sequential roles in AC specification and differentiation and that the functional dimer is targeted for degradation in VUs, the “opposite” fate. The findings indicate that dimerization-driven regulation of bHLH protein stability may be a conserved mechanism for differential regulation in specific cell contexts. E proteins are conserved regulators of growth and development. We show that the Caenorhabditis elegans E-protein helix–loop–helix-2 (HLH-2) functions as a homodimer in directing development and function of the anchor cell (AC) of the gonad, the critical organizer of uterine and vulval development. Our structure–function analysis of HLH-2 indicates that dimerization drives its degradation in other uterine cells (ventral uterine precursor cells [VUs]) that initially have potential to be the AC. We also provide evidence that this mode of dimerization-driven down-regulation can target other basic HLH (bHLH) dimers as well. Remarkably, human E proteins can functionally substitute for C. elegans HLH-2 in regulating AC development and also display dimerization-dependent degradation in VUs. Our results suggest that dimerization-driven regulation of bHLH protein stability may be a conserved mechanism for differential regulation in specific cell contexts.
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21
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Meighan CM, Kann AP, Egress ER. Transcription factor hlh-2/E/Daughterless drives expression of α integrin ina-1 during DTC migration in C. elegans. Gene 2015; 568:220-6. [PMID: 25982859 DOI: 10.1016/j.gene.2015.05.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 05/08/2015] [Accepted: 05/12/2015] [Indexed: 11/24/2022]
Abstract
Integrins are involved in a vast number of cell behaviors due to their roles in adhesion and signaling. The regulation of integrin expression is of particular interest as a mechanism to drive developmental events and for the role of altered integrin expression profiles in cancer. Dynamic regulation of the expression of integrin receptors is required for the migration of the distal tip cell (DTC) during gonadogenesis in Caenorhabditis elegans. α integrin ina-1 is required for DTC motility, yet is up-regulated by an unknown mechanism. Analysis of the promoter for α integrin ina-1 identified two E-box sequences that are required for ina-1 expression in the DTC. Knockdown of transcription factor hlh-2, an established E-box binding partner and ortholog of E/Daughterless, prevented expression of a transcriptional fusion of the ina-1 promoter to RFP and blocked DTC migration. Similarly, knockdown of hlh-2 also prevented expression of a translational fusion of the genomic ina-1 gene to GFP while blocking DTC migration. Knockdown of HLH-2 binding partner MIG-24 also reduced ina-1 expression and DTC migration. Overall, these results show that the transcription factor hlh-2 is required for up-regulation of ina-1 at the onset of DTC migration.
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Affiliation(s)
| | - Allison P Kann
- Christopher Newport University, Newport News, VA 23606, USA.
| | - Emily R Egress
- Christopher Newport University, Newport News, VA 23606, USA.
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22
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Fischer B, Azim K, Hurtado-Chong A, Ramelli S, Fernández M, Raineteau O. E-proteins orchestrate the progression of neural stem cell differentiation in the postnatal forebrain. Neural Dev 2014; 9:23. [PMID: 25352248 PMCID: PMC4274746 DOI: 10.1186/1749-8104-9-23] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 10/08/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Neural stem cell (NSC) differentiation is a complex multistep process that persists in specific regions of the postnatal forebrain and requires tight regulation throughout life. The transcriptional control of NSC proliferation and specification involves Class II (proneural) and Class V (Id1-4) basic helix-loop-helix (bHLH) proteins. In this study, we analyzed the pattern of expression of their dimerization partners, Class I bHLH proteins (E-proteins), and explored their putative role in orchestrating postnatal subventricular zone (SVZ) neurogenesis. RESULTS Overexpression of a dominant-negative form of the E-protein E47 (dnE47) confirmed a crucial role for bHLH transcriptional networks in postnatal neurogenesis by dramatically blocking SVZ NSC differentiation. In situ hybridization was used in combination with RT-qPCR to measure and compare the level of expression of E-protein transcripts (E2-2, E2A, and HEB) in the neonatal and adult SVZ as well as in magnetic affinity cell sorted progenitor cells and neuroblasts. Our results evidence that E-protein transcripts, in particular E2-2 and E2A, are enriched in the postnatal SVZ with expression levels increasing as cells engage towards neuronal differentiation. To investigate the role of E-proteins in orchestrating lineage progression, both in vitro and in vivo gain-of-function and loss-of-function experiments were performed for individual E-proteins. Overexpression of E2-2 and E2A promoted SVZ neurogenesis by enhancing not only radial glial cell differentiation but also cell cycle exit of their progeny. Conversely, knock-down by shRNA electroporation resulted in opposite effects. Manipulation of E-proteins and/or Ascl1 in SVZ NSC cultures indicated that those effects were Ascl1 dependent, although they could not solely be attributed to an Ascl1-induced switch from promoting cell proliferation to triggering cell cycle arrest and differentiation. CONCLUSIONS In contrast to former concepts, suggesting ubiquitous expression and subsidiary function for E-proteins to foster postnatal neurogenesis, this work unveils E-proteins as being active players in the orchestration of postnatal SVZ neurogenesis.
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Affiliation(s)
| | | | | | | | | | - Olivier Raineteau
- Brain Research Institute, ETH Zurich/University of Zurich, 8057 Zurich, Switzerland.
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23
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Sherlekar AL, Lints R. Nematode Tango Milonguero – The C. elegans male's search for the hermaphrodite vulva. Semin Cell Dev Biol 2014; 33:34-41. [DOI: 10.1016/j.semcdb.2014.05.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 04/24/2014] [Accepted: 05/07/2014] [Indexed: 12/31/2022]
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24
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Quednow BB, Brzózka MM, Rossner MJ. Transcription factor 4 (TCF4) and schizophrenia: integrating the animal and the human perspective. Cell Mol Life Sci 2014; 71:2815-35. [PMID: 24413739 PMCID: PMC11113759 DOI: 10.1007/s00018-013-1553-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 12/04/2013] [Accepted: 12/30/2013] [Indexed: 02/06/2023]
Abstract
Schizophrenia is a genetically complex disease considered to have a neurodevelopmental pathogenesis and defined by a broad spectrum of positive and negative symptoms as well as cognitive deficits. Recently, large genome-wide association studies have identified common alleles slightly increasing the risk for schizophrenia. Among the few schizophrenia-risk genes that have been consistently replicated is the basic Helix-Loop-Helix (bHLH) transcription factor 4 (TCF4). Haploinsufficiency of the TCF4 (formatting follows IUPAC nomenclature: TCF4 protein/protein function, Tcf4 rodent gene cDNA mRNA, TCF4 human gene cDNA mRNA) gene causes the Pitt-Hopkins syndrome-a neurodevelopmental disease characterized by severe mental retardation. Accordingly, Tcf4 null-mutant mice display developmental brain defects. TCF4-associated risk alleles are located in putative coding and non-coding regions of the gene. Hence, subtle changes at the level of gene expression might be relevant for the etiopathology of schizophrenia. Behavioural phenotypes obtained with a mouse model of slightly increased gene dosage and electrophysiological investigations with human risk-allele carriers revealed an overlapping spectrum of schizophrenia-relevant endophenotypes. Most prominently, early information processing and higher cognitive functions appear to be associated with TCF4 risk genotypes. Moreover, a recent human study unravelled gene × environment interactions between TCF4 risk alleles and smoking behaviour that were specifically associated with disrupted early information processing. Taken together, TCF4 is considered as an integrator ('hub') of several bHLH networks controlling critical steps of various developmental, and, possibly, plasticity-related transcriptional programs in the CNS and changes of TCF4 expression also appear to affect brain networks important for information processing. Consequently, these findings support the neurodevelopmental hypothesis of schizophrenia and provide a basis for identifying the underlying molecular mechanisms.
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Affiliation(s)
- Boris B. Quednow
- Department of Psychiatry, Psychotherapy and Psychosomatics, Experimental and Clinical Pharmacopsychology, Psychiatric Hospital, University of Zurich, Lenggstrasse 31, 8032 Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Magdalena M. Brzózka
- Department of Psychiatry, Molecular and Behavioral Neurobiology, Ludwig-Maximillians-University, Nussbaumstr. 7, 80336 Munich, Germany
| | - Moritz J. Rossner
- Department of Psychiatry, Molecular and Behavioral Neurobiology, Ludwig-Maximillians-University, Nussbaumstr. 7, 80336 Munich, Germany
- Research Group Gene Expression, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, Goettingen, 37075 Germany
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25
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Emmons SW. The development of sexual dimorphism: studies of the Caenorhabditis elegans male. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2014; 3:239-62. [PMID: 25262817 PMCID: PMC4181595 DOI: 10.1002/wdev.136] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 04/02/2014] [Indexed: 01/09/2023]
Abstract
Studies of the development of the Caenorhabditis elegans male have been carried out with the aim of understanding the basis of sexual dimorphism. Postembryonic development of the two C. elegans sexes differs extensively. Development along either the hermaphrodite or male pathway is specified initially by the X to autosome ratio. The regulatory events initiated by this ratio include a male-determining paracrine intercellular signal. Expression of this signal leads to different consequences in three regions of the body: the nongonadal soma, the somatic parts of the gonad, and the germ line. In the nongonadal soma, activity of the key Zn-finger transcription factor TRA-1 determines hermaphrodite development; in its absence, the male pathway is followed. Only a few genes directly regulated by TRA-1 are currently known, including members of the evolutionarily conserved, male-determining DM domain Zn-finger transcription factors. In the somatic parts of the gonad and germ line, absence of TRA-1 activity is not sufficient for full expression of the male pathway. Several additional transcription factors involved have been identified. In the germ line, regulatory genes for sperm development that act at the level of RNA in the cytoplasm play a prominent role.
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Affiliation(s)
- Scott W. Emmons
- Albert Einstein College of Medicine 1300 Morris Park Ave. Bronx, New York 10461
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26
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Zhu Z, Liu J, Yi P, Tian D, Chai Y, Li W, Ou G. A proneural gene controls C. elegans neuroblast asymmetric division and migration. FEBS Lett 2014; 588:1136-43. [PMID: 24589937 DOI: 10.1016/j.febslet.2014.02.036] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 02/14/2014] [Indexed: 12/12/2022]
Abstract
Proneural genes control the generation of neuroblasts from the neuroepithelium, but their functions in neuroblast asymmetric division and migration remain elusive. Here, we identified Caenorhabditiselegans mutants of a proneural transcription factor (TF) lin-32, in which Q neuroblasts are produced. We showed that LIN-32 functions in parallel with a storkhead TF, HAM-1, to regulate Q neuroblast asymmetric division, and that Q neuroblast migration is inhibited in lin-32 alleles. Consistently, lin-32 is expressed throughout Q neuroblast lineage, suggesting that LIN-32 may promote different target gene expression. Our studies thus uncovered previously unknown functions of a proneural gene in neuroblast development.
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Affiliation(s)
- Zhiwen Zhu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China
| | - Jianhong Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing, China
| | - Peishan Yi
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing, China
| | - Dong Tian
- Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yongping Chai
- Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Wei Li
- School of Medicine, Tsinghua University, Beijing 100084, China
| | - Guangshuo Ou
- Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
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Dalpe G, Tarsitano M, Persico MG, Zheng H, Culotti J. C. elegans PVF-1 inhibits permissive UNC-40 signalling through CED-10 GTPase to position the male ray 1 sensillum. Development 2013; 140:4020-4030. [PMID: 24004945 DOI: 10.1242/dev.095190] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2025]
Abstract
Graded distributions of netrin and semaphorin guidance cues convey instructive polarity information to migrating cells and growth cones, but also have permissive (i.e. non-polarity determining) functions in mammalian development and repair. The permissive functions of these cues are largely uncharacterised at a molecular level. We found previously that UNC-6 (netrin) signals permissively through UNC-40 (DCC) and UNC-5 receptors to prevent anterior displacement of the ray 1 sensillum in the C. elegans male tail. UNC-6/UNC-40 signalling functions in parallel with SMP-1 (semaporin 1)/PLX-1 (plexin) signalling to prevent this defect. Here, we report that a deletion allele of pvf-1, which encodes a VEGF-related protein, causes no ray 1 defects, but enhances ray 1 defects of a plx-1 mutant, and unexpectedly also suppresses unc-6(ev400)-null mutant ray 1 defects. These mutant ray 1 inductive and suppressive effects are mimicked by the ability of unc-40(+) and ced-10(gain-of-function) multi-copy transgene arrays to induce ray 1 defects or suppress unc-6 mutant ray 1 defects, depending on their dosage, suggesting the pvf-1 mutation causes UNC-40 overactivity that interferes with signalling but is partially sensitive to UNC-6. Additional data suggest PVF-1 functions through four VEGF receptor-related proteins and inhibits only CED-10 (a GTPase), but not MIG-2-dependent UNC-40 activity, even though UNC-40 functions through both GTPases to position ray 1. pvf-1 and receptor mutant ray 1 defects are rescued by transgenes expressing mouse VEGF164 and human VEGF receptors, respectively. These data report the first case of VEGF-induced inhibition of the netrin signalling and a molecular conservation of VEGF function from worms to humans.
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Affiliation(s)
- Gratien Dalpe
- Samuel Lunenfeld Research Institute of Mount Sinai Hospital, Toronto, Ontario, M5G 1X5, Canada
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Duncan JS, Fritzsch B. Evolution of Sound and Balance Perception: Innovations that Aggregate Single Hair Cells into the Ear and Transform a Gravistatic Sensor into the Organ of Corti. Anat Rec (Hoboken) 2012; 295:1760-74. [DOI: 10.1002/ar.22573] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 07/24/2012] [Indexed: 01/20/2023]
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Semaphorin-1 and netrin signal in parallel and permissively to position the male ray 1 sensillum in Caenorhabditis elegans. Genetics 2012; 192:959-71. [PMID: 22942127 DOI: 10.1534/genetics.112.144253] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Netrin and semaphorin axon guidance cues have been found to function in the genesis of several mammalian organs; however, little is known about the underlying molecular mechanisms involved. A genetic approach could help to reveal the underpinnings of these mechanisms. The most anterior ray sensillum (ray 1) in the Caenorhabditis elegans male tail is frequently displaced anterior to its normal position in smp-1/semaphorin-1a and plexin-1/plx-1 mutants. Here we report that UNC-6/netrin and its UNC-40/DCC receptor signal in parallel to SMP-1/semaphorin-1a and its PLX-1/plexin-1 receptor to prevent the anterior displacement of ray 1 and that UNC-6 plus SMP-1 signaling can account entirely for this function. We also report that mab-20/semaphorin-2a mutations, which prevent the separation of neighboring rays and cause ray fusions, suppress the anterior displacements of ray 1 caused by deficiencies in SMP-1 and UNC-6 signaling and this is independent of the ray fusion phenotype, whereas overexpression of UNC-40 and PLX-1 cause ray fusions. This suggests that for ray 1 positioning, a balance is struck between a tendency of SMP-1 and UNC-6 signaling to prevent ray 1 from moving away from ray 2 and a tendency of MAB-20/semaphorin-2a signaling to separate all rays from each other. Additional evidence suggests this balance involves the relative adhesion of the ray 1 structural cell to neighboring SET and hyp 7 hypodermal cells. This finding raises the possibility that changes in ray 1 positioning depend on passive movements caused by attachment to the elongating SET cell in opposition to the morphologically more stable hyp 7 cell. Several lines of evidence indicate that SMP-1 and UNC-6 function permissively in the context of ray 1 positioning.
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Philogene MC, Small SGM, Wang P, Corsi AK. Distinct Caenorhabditis elegans HLH-8/twist-containing dimers function in the mesoderm. Dev Dyn 2012; 241:481-92. [PMID: 22275075 DOI: 10.1002/dvdy.23734] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2012] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND The Caenorhabditis elegans basic helix-loop-helix (bHLH) factor HLH-8, the single Twist ortholog in the nematode genome, plays important roles in mesoderm development, including M lineage patterning and differentiation of vulval and enteric muscles. HLH-8 cooperates with HLH-2, the bHLH E/Daughterless ortholog, to regulate downstream target genes, but it is not known whether HLH-2 is an obligate partner for all HLH-8 functions. RESULTS Using hlh-2 loss-of-function alleles and RNAi, we discovered that HLH-2 is required in the vulval muscles but not in M patterning or enteric muscle development. Additionally, we found that expressing tethered HLH-8/HLH-8 dimers in hlh-8 null animals rescued M patterning and enteric but not vulval muscle development. CONCLUSIONS These results support a model whereby HLH-8/HLH-8 homodimers function in M lineage patterning and enteric muscles and HLH-8/HLH-2 heterodimers function in the M-derived vulval muscles. Interestingly, the different dimers function in the same M lineage cells and the switch in dimer function coincides with vulval muscle differentiation. The use of distinct Twist dimers is evolutionarily conserved, and C. elegans provides a paradigm for future dissection of differential promoter regulation by these dimers at a single cell resolution.
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Affiliation(s)
- Mary C Philogene
- Department of Biology, The Catholic University of America, Washington, DC 20064, USA
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Nukazuka A, Tamaki S, Matsumoto K, Oda Y, Fujisawa H, Takagi S. A shift of the TOR adaptor from Rictor towards Raptor by semaphorin in C. elegans. Nat Commun 2011; 2:484. [PMID: 21952218 PMCID: PMC3195255 DOI: 10.1038/ncomms1495] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 08/26/2011] [Indexed: 11/09/2022] Open
Abstract
The target of rapamycin (TOR), a central regulator for cell growth and metabolism, resides in the two functionally distinct complexes TORC1 and TORC2, which are defined by their adaptors Raptor and Rictor, respectively. How the formation of the two TORCs is orchestrated remains unclear. Here we show the control of TOR partnering by semaphorin-plexin signalling in Caenorhabditis elegans. In semaphorin and plexin mutants, TOR-Raptor association decreases whereas TOR-Rictor association increases, concomitantly with TORC1 down- and TORC2 up-regulation. Epidermal defects in the mutants are suppressed by inhibiting TORC2 or reinforcing TORC1 signalling. Conversely, inhibition of TORC1 signalling phenocopies the mutants. Thus, our results indicate that TORC formation is a singularly important step in semaphorin signalling that culminates in diverse outcomes including TORC1-promoted messenger RNA translation and TORC2-regulated cytoskeletal remodelling.
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Affiliation(s)
- Akira Nukazuka
- Division of Biological Science, Nagoya University Graduate School of Science, Chikusa-ku, Nagoya 464-8602, Japan
| | - Shusaku Tamaki
- Division of Biological Science, Nagoya University Graduate School of Science, Chikusa-ku, Nagoya 464-8602, Japan
| | - Kunihiro Matsumoto
- Division of Biological Science, Nagoya University Graduate School of Science, Chikusa-ku, Nagoya 464-8602, Japan
| | - Yoichi Oda
- Division of Biological Science, Nagoya University Graduate School of Science, Chikusa-ku, Nagoya 464-8602, Japan
| | - Hajime Fujisawa
- Division of Biological Science, Nagoya University Graduate School of Science, Chikusa-ku, Nagoya 464-8602, Japan
| | - Shin Takagi
- Division of Biological Science, Nagoya University Graduate School of Science, Chikusa-ku, Nagoya 464-8602, Japan
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32
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Bertrand V, Bisso P, Poole RJ, Hobert O. Notch-dependent induction of left/right asymmetry in C. elegans interneurons and motoneurons. Curr Biol 2011; 21:1225-31. [PMID: 21737278 PMCID: PMC3233726 DOI: 10.1016/j.cub.2011.06.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 06/06/2011] [Accepted: 06/07/2011] [Indexed: 02/03/2023]
Abstract
Although nervous systems are largely bilaterally symmetric on a structural level, they display striking degrees of functional left/right (L/R) asymmetry. In Caenorhabditis elegans, two structurally symmetric pairs of sensory neurons, ASE and AWC, display two distinctly controlled types of functional L/R asymmetries (stereotyped versus stochastic asymmetry). Beyond these two cases, the extent of neuronal asymmetry in the C. elegans nervous system was unclear. Here, we report that the Beta3/Olig-type bHLH transcription factor hlh-16 is L/R asymmetrically expressed in several distinct, otherwise bilaterally symmetric interneuron and motoneuron pairs that are part of a known navigation circuit. We find that hlh-16 asymmetry is generated during gastrulation by an asymmetric LAG-2/Delta signal originating from the mesoderm that promotes hlh-16 expression in neurons on the left side through direct binding of the Notch effector LAG-1/Su(H)/CBF to a cis-regulatory element in the hlh-16 locus. Removal of hlh-16 reveals an unanticipated asymmetry in the ability of the axons of the AIY interneurons to extend into the nerve ring, with the left AIY axon requiring elevated hlh-16 expression for correct extension. Our study suggests that the extent of molecular L/R asymmetry in the C. elegans nervous system is broader than previously anticipated, establishes a novel signaling mechanism that crosses germ layers to diversify bilaterally symmetric neuronal lineages, and reveals L/R asymmetric control of axonal outgrowth of bilaterally symmetric neurons.
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Affiliation(s)
- Vincent Bertrand
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University Medical Center, New York, NY 10032, USA.
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33
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Schindler AJ, Sherwood DR. The transcription factor HLH-2/E/Daughterless regulates anchor cell invasion across basement membrane in C. elegans. Dev Biol 2011; 357:380-91. [PMID: 21784067 DOI: 10.1016/j.ydbio.2011.07.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Revised: 06/17/2011] [Accepted: 07/07/2011] [Indexed: 10/18/2022]
Abstract
Cell invasion through basement membrane is a specialized cellular behavior critical for many developmental processes and leukocyte trafficking. Invasive cellular behavior is also inappropriately co-opted during cancer progression. Acquisition of an invasive phenotype is accompanied by changes in gene expression that are thought to coordinate the steps of invasion. The transcription factors responsible for these changes in gene expression, however, are largely unknown. C. elegans anchor cell (AC) invasion is a genetically tractable in vivo model of invasion through basement membrane. AC invasion requires the conserved transcription factor FOS-1A, but other transcription factors are thought to act in parallel to FOS-1A to control invasion. Here we identify the transcription factor HLH-2, the C. elegans ortholog of Drosophila Daughterless and vertebrate E proteins, as a regulator of AC invasion. Reduction of HLH-2 function by RNAi or with a hypomorphic allele causes defects in AC invasion. Genetic analysis indicates that HLH-2 has functions outside of the FOS-1A pathway. Using expression analysis, we identify three genes that are transcriptionally regulated by HLH-2: the protocadherin cdh-3, and two genes encoding secreted extracellular matrix proteins, mig-6/papilin and him-4/hemicentin. Further, we show that reduction of HLH-2 function causes defects in polarization of F-actin to the invasive cell membrane, a process required for the AC to generate protrusions that breach the basement membrane. This work identifies HLH-2 as a regulator of the invasive phenotype in the AC, adding to our understanding of the transcriptional networks that control cell invasion.
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Poole RJ, Bashllari E, Cochella L, Flowers EB, Hobert O. A Genome-Wide RNAi Screen for Factors Involved in Neuronal Specification in Caenorhabditis elegans. PLoS Genet 2011; 7:e1002109. [PMID: 21698137 PMCID: PMC3116913 DOI: 10.1371/journal.pgen.1002109] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 04/14/2011] [Indexed: 11/19/2022] Open
Abstract
One of the central goals of developmental neurobiology is to describe and understand the multi-tiered molecular events that control the progression of a fertilized egg to a terminally differentiated neuron. In the nematode Caenorhabditis elegans, the progression from egg to terminally differentiated neuron has been visually traced by lineage analysis. For example, the two gustatory neurons ASEL and ASER, a bilaterally symmetric neuron pair that is functionally lateralized, are generated from a fertilized egg through an invariant sequence of 11 cellular cleavages that occur stereotypically along specific cleavage planes. Molecular events that occur along this developmental pathway are only superficially understood. We take here an unbiased, genome-wide approach to identify genes that may act at any stage to ensure the correct differentiation of ASEL. Screening a genome-wide RNAi library that knocks-down 18,179 genes (94% of the genome), we identified 245 genes that affect the development of the ASEL neuron, such that the neuron is either not generated, its fate is converted to that of another cell, or cells from other lineage branches now adopt ASEL fate. We analyze in detail two factors that we identify from this screen: (1) the proneural gene hlh-14, which we find to be bilaterally expressed in the ASEL/R lineages despite their asymmetric lineage origins and which we find is required to generate neurons from several lineage branches including the ASE neurons, and (2) the COMPASS histone methyltransferase complex, which we find to be a critical embryonic inducer of ASEL/R asymmetry, acting upstream of the previously identified miRNA lsy-6. Our study represents the first comprehensive, genome-wide analysis of a single neuronal cell fate decision. The results of this analysis provide a starting point for future studies that will eventually lead to a more complete understanding of how individual neuronal cell types are generated from a single-cell embryo.
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Affiliation(s)
- Richard J. Poole
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University Medical Center, New York, New York, United States of America
- * E-mail: (RJP); (OH)
| | - Enkelejda Bashllari
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University Medical Center, New York, New York, United States of America
| | - Luisa Cochella
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University Medical Center, New York, New York, United States of America
| | - Eileen B. Flowers
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University Medical Center, New York, New York, United States of America
| | - Oliver Hobert
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University Medical Center, New York, New York, United States of America
- * E-mail: (RJP); (OH)
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35
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Kuzin A, Kundu M, Brody T, Odenwald WF. Functional analysis of conserved sequences within a temporally restricted neural precursor cell enhancer. Mech Dev 2011; 128:165-77. [PMID: 21315151 PMCID: PMC3095431 DOI: 10.1016/j.mod.2011.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 01/28/2011] [Accepted: 02/02/2011] [Indexed: 11/18/2022]
Abstract
Many of the key regulators of Drosophila CNS neural identity are expressed in defined temporal orders during neuroblast (NB) lineage development. To begin to understand the structural and functional complexity of enhancers that regulate ordered NB gene expression programs, we have undertaken the mutational analysis of the temporally restricted nerfin-1 NB enhancer. Our previous studies have localized the enhancer to a region just proximal to the nerfin-1 transcription start site. Analysis of this enhancer, using the phylogenetic footprint program EvoPrinter, reveals the presence of multiple sequence blocks that are conserved among drosophilids. cis-Decoder alignments of these conserved sequence blocks (CSBs) has identified shorter elements that are conserved in other Drosophila NB enhancers. Mutagenesis of the enhancer reveals that although each CSB is required for wild-type expression, neither position nor orientation of the CSBs within the enhancer is crucial for enhancer function; removal of less-conserved or non-conserved sequences flanking CSB clusters also does not significantly alter enhancer activity. While all three conserved E-box transcription factor (TF) binding sites (CAGCTG) are required for full function, adding an additional site at different locations within non-conserved sequences interferes with enhancer activity. Of particular note, none of the mutations resulted in ectopic reporter expression outside of the early NB expression window, suggesting that the temporally restricted pattern is defined by transcriptional activators and not by direct DNA binding repressors. Our work also points to an unexpectedly large number of TFs required for optimal enhancer function - mutant TF analysis has identified at least four that are required for full enhancer regulation.
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Affiliation(s)
- Alexander Kuzin
- Neural Cell-Fate Determinants Section, NINDS, NIH Bethesda, Maryland, USA
| | - Mukta Kundu
- Neural Cell-Fate Determinants Section, NINDS, NIH Bethesda, Maryland, USA
| | - Thomas Brody
- Neural Cell-Fate Determinants Section, NINDS, NIH Bethesda, Maryland, USA
| | - Ward F. Odenwald
- Neural Cell-Fate Determinants Section, NINDS, NIH Bethesda, Maryland, USA
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36
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Sengupta P, Schedl T. Cellular reprogramming: chromatin puts on the brake. Curr Biol 2011; 21:R157-9. [PMID: 21334296 DOI: 10.1016/j.cub.2010.12.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Directed reprogramming of differentiated cells allows the generation of specific cell types for therapeutics and can provide unexpected insights into development. A recent study demonstrates that efficient reprogramming of Caenorhabditis elegans germ cells into neurons can be achieved by knocking down a histone chaperone gene and ectopic expression of a terminal selector transcription factor.
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Affiliation(s)
- Piali Sengupta
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, USA.
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37
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Lee SU, Song HO, Lee W, Singaravelu G, Yu JR, Park WY. Identification and characterization of a putative basic helix-loop-helix (bHLH) transcription factor interacting with calcineurin in C. elegans. Mol Cells 2009; 28:455-61. [PMID: 19855932 DOI: 10.1007/s10059-009-0145-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Accepted: 08/31/2009] [Indexed: 11/26/2022] Open
Abstract
Calcineurin is a Ca(2+)/Calmodulin activated Ser/Thr phosphatase that is well conserved from yeast to human. It is composed of catalytic subunit A (CnA) and regulatory subunit B (CnB). C. elegans homolog of CnA and CnB has been annotated to tax-6 and cnb-1, respectively and in vivo function of both genes has been intensively studied. In C. elegans, calcineurin play roles in various signaling pathways such as fertility, movement, body size regulation and serotonin-mediated egg laying. In order to understand additional signaling pathway(s) in which calcineurin functions, we screened for binding proteins of TAX-6 and found a novel binding protein, HLH-11. The HLH-11, a member of basic helix-loop-helix (bHLH) proteins, is a putative counterpart of human AP4 transcription factor. Previously bHLH transcription factors have been implicated to regulate many developmental processes such as cell proliferation and differentiation, sex determination and myogenesis. However, the in vivo function of hlh-11 is largely unknown. Here, we show that hlh-11 is expressed in pharynx, intestine, nerve cords, anal depressor and vuvla muscles where calcineurin is also expressed. Mutant analyses reveal that hlh-11 may have role(s) in regulating body size and reproduction. More interestingly, genetic epistasis suggests that hlh-11 may function to regulate serotonin-mediated egg laying at the downstream of tax-6.
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Affiliation(s)
- Soo-Ung Lee
- Department of Environmental and Tropical Medicine, Konkuk University School of Medicine, Seoul 143-701, Korea
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38
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Grove CA, de Masi F, Barrasa MI, Newburger DE, Alkema MJ, Bulyk ML, Walhout AJ. A multiparameter network reveals extensive divergence between C. elegans bHLH transcription factors. Cell 2009; 138:314-27. [PMID: 19632181 PMCID: PMC2774807 DOI: 10.1016/j.cell.2009.04.058] [Citation(s) in RCA: 211] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Revised: 03/06/2009] [Accepted: 04/23/2009] [Indexed: 01/20/2023]
Abstract
Differences in expression, protein interactions, and DNA binding of paralogous transcription factors ("TF parameters") are thought to be important determinants of regulatory and biological specificity. However, both the extent of TF divergence and the relative contribution of individual TF parameters remain undetermined. We comprehensively identify dimerization partners, spatiotemporal expression patterns, and DNA-binding specificities for the C. elegans bHLH family of TFs, and model these data into an integrated network. This network displays both specificity and promiscuity, as some bHLH proteins, DNA sequences, and tissues are highly connected, whereas others are not. By comparing all bHLH TFs, we find extensive divergence and that all three parameters contribute equally to bHLH divergence. Our approach provides a framework for examining divergence for other protein families in C. elegans and in other complex multicellular organisms, including humans. Cross-species comparisons of integrated networks may provide further insights into molecular features underlying protein family evolution. For a video summary of this article, see the PaperFlick file available with the online Supplemental Data.
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Affiliation(s)
- Christian A. Grove
- Program in Gene Function and Expression and Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Federico de Masi
- Division of Genetics, Department of Medicine, Brigham & Women’s Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - M. Inmaculada Barrasa
- Program in Gene Function and Expression and Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Daniel E. Newburger
- Division of Genetics, Department of Medicine, Brigham & Women’s Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Mark J. Alkema
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Martha L. Bulyk
- Division of Genetics, Department of Medicine, Brigham & Women’s Hospital and Harvard Medical School, Boston, MA 02115, USA
- Department of Pathology, Brigham & Women’s Hospital and Harvard Medical School, Boston, MA 02115, USA
- Harvard-MIT Division of Health Sciences & Technology, Harvard Medical School, Boston, MA 02115, USA
| | - Albertha J.M. Walhout
- Program in Gene Function and Expression and Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
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Chesney MA, Lam N, Morgan DE, Phillips BT, Kimble J. C. elegans HLH-2/E/Daughterless controls key regulatory cells during gonadogenesis. Dev Biol 2009; 331:14-25. [PMID: 19376107 PMCID: PMC2776051 DOI: 10.1016/j.ydbio.2009.04.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Revised: 03/20/2009] [Accepted: 04/13/2009] [Indexed: 12/23/2022]
Abstract
The Caenorhabditis elegans distal tip cell (DTC) provides a niche for germline stem cells in both hermaphrodites and males. The hermaphrodite distal tip cell (hDTC) also provides "leader" function to control gonadal elongation and shape, while in males, leader function is allocated to the linker cell (LC). Therefore, the male distal tip cell (mDTC) serves as a niche but not as a leader. The C. elegans homolog of E/Daughterless, HLH-2, was previously implicated in hDTC specification. Here we report that HLH-2 is also critical for hDTC maintenance, hDTC niche function and hDTC expression of a lag-2/DSL ligand reporter. We also find that HLH-2 functions in males to direct linker cell specification and to promote both mDTC maintenance and the mDTC niche function. We conclude that HLH-2 functions in both sexes to promote leader cell specification and DTC niche function.
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Affiliation(s)
- Michael A. Chesney
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Ngan Lam
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Dyan E. Morgan
- Program in Cellular and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
| | - Bryan T. Phillips
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Judith Kimble
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
- Program in Cellular and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI 53706
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Nukazuka A, Fujisawa H, Inada T, Oda Y, Takagi S. Semaphorin controls epidermal morphogenesis by stimulating mRNA translation via eIF2alpha in Caenorhabditis elegans. Genes Dev 2008; 22:1025-36. [PMID: 18413715 DOI: 10.1101/gad.1644008] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Conserved semaphorin-plexin signaling systems govern various aspects of animal development, including axonal guidance in vertebrates and epidermal morphogenesis in Caenorhabditis elegans. Here we provide in vivo evidence that stimulation of mRNA translation via eukaryotic initiation factor 2alpha (eIF2alpha) is an essential downstream event of semaphorin signaling in C. elegans. In semaphorin/plexin mutants, a marked elevation in the phosphorylation of eIF2alpha is observed, which causes translation repression and is causally related to the morphological epidermal phenotype in the mutants. Conversely, removal of constraints on translation by genetically reducing the eIF2alpha phosphorylation largely bypasses requirement for the semaphorin signal in epidermal morphogenesis. We also identify an actin-depolymerizing factor/cofilin, whose expression in the mutants is predominantly repressed, as a major translational target of semaphorin signaling. Thus, our results reveal a physiological significance for translation of mRNAs for cytoskeletal regulators, linking environmental cues to cytoskeletal rearrangement during cellular morphogenesis in vivo.
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Affiliation(s)
- Akira Nukazuka
- Division of Biological Science, Nagoya University Graduate School of Science, Chikusa-ku, Nagoya 464-8602, Japan
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Doonan R, Hatzold J, Raut S, Conradt B, Alfonso A. HLH-3 is a C. elegans Achaete/Scute protein required for differentiation of the hermaphrodite-specific motor neurons. Mech Dev 2008; 125:883-93. [PMID: 18586090 DOI: 10.1016/j.mod.2008.06.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Revised: 05/28/2008] [Accepted: 06/02/2008] [Indexed: 10/22/2022]
Abstract
Basic helix-loop-helix (bHLH) proteins of the Achaete/Scute (Ac/Sc) family are required for neurogenesis in both Drosophila and vertebrates. These transcription factors are commonly referred to as 'proneural' factors, as they promote neural fate in many contexts. Although Ac/Sc proteins have been studied in Hydra, jellyfish, many insects, and several vertebrates, the role of these proteins in Caenorhabditis elegans neurogenesis is relatively uncharacterized. The C. elegans genome consists of three Ac/Sc genes, previously identified as hlh-3, hlh-6, and hlh-14. Here, we characterize the role of hlh-3 in nervous system development. Although hlh-3 appears to be expressed in all neural precursors, we find that hlh-3 null mutants have a mostly functional nervous system. However, these mutants are egg-laying defective, resulting from a block in differentiation of the HSN motor neurons. Detectable HSNs have misdirected axon projection, which appears to result from a lack of netrin signaling within the HSNs. Thus, our findings suggest a novel link between Ac/Sc bHLH proteins and the expression of genes required for proper interpretation of axon guidance cues. Lastly, based on sequence identity, expression pattern, and a role in neural differentiation, hlh-3 is most likely an ortholog of Drosophila asense.
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Affiliation(s)
- Ryan Doonan
- Department of Biology, University College London, London, England WC1E 6BT, UK.
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Wolff JR, Zarkower D. Chapter 1 Somatic Sexual Differentiation in Caenorhabditis elegans. Curr Top Dev Biol 2008; 83:1-39. [DOI: 10.1016/s0070-2153(08)00401-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Nakao F, Hudson ML, Suzuki M, Peckler Z, Kurokawa R, Liu Z, Gengyo-Ando K, Nukazuka A, Fujii T, Suto F, Shibata Y, Shioi G, Fujisawa H, Mitani S, Chisholm AD, Takagi S. The PLEXIN PLX-2 and the ephrin EFN-4 have distinct roles in MAB-20/Semaphorin 2A signaling in Caenorhabditis elegans morphogenesis. Genetics 2007; 176:1591-607. [PMID: 17507686 PMCID: PMC1931547 DOI: 10.1534/genetics.106.067116] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2006] [Accepted: 04/24/2007] [Indexed: 01/24/2023] Open
Abstract
Semaphorins are extracellular proteins that regulate axon guidance and morphogenesis by interacting with a variety of cell surface receptors. Most semaphorins interact with plexin-containing receptor complexes, although some interact with non-plexin receptors. Class 2 semaphorins are secreted molecules that control axon guidance and epidermal morphogenesis in Drosophila and Caenorhabditis elegans. We show that the C. elegans class 2 semaphorin MAB-20 binds the plexin PLX-2. plx-2 mutations enhance the phenotypes of hypomorphic mab-20 alleles but not those of mab-20 null alleles, indicating that plx-2 and mab-20 act in a common pathway. Both mab-20 and plx-2 mutations affect epidermal morphogenesis during embryonic and in postembryonic development. In both contexts, plx-2 null mutant phenotypes are much less severe than mab-20 null phenotypes, indicating that PLX-2 is not essential for MAB-20 signaling. Mutations in the ephrin efn-4 do not synergize with mab-20, indicating that EFN-4 may act in MAB-20 signaling. EFN-4 and PLX-2 are coexpressed in the late embryonic epidermis where they play redundant roles in MAB-20-dependent cell sorting.
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Affiliation(s)
- Fumi Nakao
- Division of Biological Science, Nagoya University Graduate School of Science, Nagoya, Japan
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Tamai KK, Nishiwaki K. bHLH transcription factors regulate organ morphogenesis via activation of an ADAMTS protease in C. elegans. Dev Biol 2007; 308:562-71. [PMID: 17588558 DOI: 10.1016/j.ydbio.2007.05.024] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 04/26/2007] [Accepted: 05/18/2007] [Indexed: 11/20/2022]
Abstract
The ADAMTS (a disintegrin and metalloprotease with thrombospondin motifs) family of secreted metalloproteases plays important roles in animal development and pathogenesis. However, transcriptional regulation of ADAMTS proteins during development remains largely unexplored. Here we show that basic helix-loop-helix (bHLH) transcription factors regulate the expression of an ADAMTS protease that is required for gonad development in Caenorhabditis elegans. Mutations in the gene mig-24 cause shortened and swollen gonad arms due to a defect in gonadal leader cell migration, although leader cell specification appears to occur normally. The MIG-24 protein is a bHLH transcription factor of the Achaete-Scute family and is specifically expressed in gonadal leader cells. MIG-24 can physically interact with HLH-2, an E/Daughterless family bHLH transcription factor and bind the promoter region of gon-1, which encodes an ADAMTS protease required for gonadal leader cell migration. Mutations or RNA interference of mig-24 and hlh-2 severely impaired gon-1 expression and forced expression of GON-1 in leader cells in mig-24 mutants partially rescued the gonadal elongation defect. We propose that, unlike most previously characterized Achaete-Scute transcription factors that are involved in cell fate specification, MIG-24 acts with HLH-2 in specified cells to control cell migration by activating the expression of the GON-1 ADAMTS protease.
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Affiliation(s)
- Katsuyuki K Tamai
- RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan.
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Portman DS. Genetic control of sex differences in C. elegans neurobiology and behavior. ADVANCES IN GENETICS 2007; 59:1-37. [PMID: 17888793 DOI: 10.1016/s0065-2660(07)59001-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
As a well-characterized, genetically tractable animal, the nematode Caenorhabditis elegans is an ideal model to explore the connections between genes and the sexual regulation of the nervous system and behavior. The two sexes of C. elegans, males and hermaphrodites, have precisely defined differences in neuroanatomy: superimposed onto a "core" nervous system of exactly 294 neurons, hermaphrodites and males have 8 and 89 sex-specific neurons, respectively. These sex-specific neurons are essential for cognate sex-specific behaviors, including hermaphrodite egg-laying and male mating. In addition, regulated sex differences in the core nervous system itself may provide additional, though poorly understood, controls on behavior. These differences in the nervous system and behavior, like all known sex differences in the C. elegans soma, are controlled by the master regulator of C. elegans sex determination, tra-1. Downstream of tra-1 lie specific effectors of sex determination, including genes controlling sex-specific cell death and a family of regulators, the DM-domain genes, related to Drosophila doublesex and the vertebrate DMRT genes. There is no central (i.e., gonadal) regulator of sexual phenotype in the C. elegans nervous system; instead, tra-1 acts cell-autonomously in nearly all sexually dimorphic somatic cells. However, recent results suggest that the status of the gonad can be communicated to the nervous system to modulate sex-specific behaviors. Continuing research into the genetic control of neural sex differences in C. elegans is likely to yield insight into conserved mechanisms of cell-autonomous cross talk between cell fate patterning and sexual differentiation pathways.
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Affiliation(s)
- Douglas S Portman
- Department of Biomedical Genetics and Center for Aging and Developmental Biology, University of Rochester, Rochester, New York 14642, USA
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Jia L, Emmons SW. Genes that control ray sensory neuron axon development in the Caenorhabditis elegans male. Genetics 2006; 173:1241-58. [PMID: 16624900 PMCID: PMC1526702 DOI: 10.1534/genetics.106.057000] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2006] [Accepted: 04/13/2006] [Indexed: 11/18/2022] Open
Abstract
We have studied how a set of male-specific sensory neurons in Caenorhabditis elegans establish axonal connections during postembryonic development. In the adult male, 9 bilateral pairs of ray sensory neurons innervate an acellular fan that serves as a presumptive tactile and olfactory organ during copulation. We visualized ray axon commissures with a ray neuron-specific reporter gene and studied both known and new mutations that affect the establishment of connections to the pre-anal ganglion. We found that the UNC-6/netrin-UNC-40/DCC pathway provides the primary dorsoventral guidance cue to ray axon growth cones. Some axon growth cones also respond to an anteroposterior cue, following a segmented pathway, and most or all also have a tendency to fasciculate. Two newly identified genes, rax-1 and rax-4, are highly specific to the ray neurons and appear to be required for ray axon growth cones to respond to the dorsoventral cue. Among other genes we identified, rax-2 and rax-3 affect anteroposterior signaling or fate specification and rax-5 and rax-6 affect ray identities. We identified a mutation in sax-2 and show that the sax-2/Furry and sax-1/Tricornered pathway affects ectopic neurite outgrowth and establishment of normal axon synapses. Finally, we identified mutations in genes for muscle proteins that affect axon pathways by distorting the conformation of the body wall. Thus ray axon pathfinding relies on a variety of general and more ray neuron-specific genes and provides a potentially fruitful system for further studies of how migrating axon growth cones locate their targets. This system is applicable to the study of mechanisms underlying topographic mapping of sensory neurons into target circuitry where the next stage of information processing is carried out.
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Affiliation(s)
- Lingyun Jia
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Aamodt E, Aamodt S. Neural specification and differentiation. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2006; 69:73-97. [PMID: 16492462 DOI: 10.1016/s0074-7742(05)69003-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Affiliation(s)
- Eric Aamodt
- Department of Biochemistry, Louisiana State University Health Sciences Center-Shreveport, Louisiana, USA
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Wang P, Zhao J, Corsi AK. Identification of novel target genes of CeTwist and CeE/DA. Dev Biol 2006; 293:486-98. [PMID: 16480708 DOI: 10.1016/j.ydbio.2005.10.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Revised: 10/03/2005] [Accepted: 10/04/2005] [Indexed: 10/25/2022]
Abstract
Twist, a basic helix-loop-helix (bHLH) transcription factor, plays an important role in mesoderm development in many organisms, including C. elegans where CeTwist is required to direct cell fate specifications of a subset of mesodermal cells. Although several target genes of CeTwist have been identified, how this protein accomplishes its function is unclear. In addition, several human genes whose mutations cause different syndromes of craniosynostosis (premature fusion of cranial sutures) have homologues in the CeTwist pathway. Identification of novel target genes of CeTwist will shed more light on the functions of CeTwist in mesoderm development, and the corresponding human homologues will be good candidates for related syndromes with unidentified mutated genes. In our study, both CeTwist and its heterodimeric partner, CeE/DA, were overexpressed from the inducible heat-shock promoter, and potential target genes were detected with Affymetrix oligonucleotide microarrays. Using transcriptional GFP reporters, we found 11 genes were expressed in cells coincident with known CeTwist target gene products. Based on subsequent validation experiments, 9 genes were defined as novel CeTwist and CeE/DA targets. Human homologues of two of these genes might be involved in craniofacial diseases, which further validates C. elegans as a good model organism for providing insights into these disorders.
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Affiliation(s)
- Peng Wang
- Department of Biology, Catholic University of America, Washington, DC 20064, USA
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Lanjuin A, Claggett J, Shibuya M, Hunter CP, Sengupta P. Regulation of neuronal lineage decisions by the HES-related bHLH protein REF-1. Dev Biol 2006; 290:139-51. [PMID: 16376329 DOI: 10.1016/j.ydbio.2005.11.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Revised: 11/08/2005] [Accepted: 11/14/2005] [Indexed: 12/12/2022]
Abstract
Members of the HES subfamily of bHLH proteins play crucial roles in neural patterning via repression of neurogenesis. In C. elegans, loss-of-function mutations in ref-1, a distant nematode-specific member of this subfamily, were previously shown to cause ectopic neurogenesis from postembryonic lineages. However, while the vast majority of the nervous system in C. elegans is generated embryonically, the role of REF-1 in regulating these neural lineage decisions is unknown. Here, we show that mutations in ref-1 result in the generation of multiple ectopic neuron types derived from an embryonic neuroblast. In wild-type animals, neurons derived from this sublineage are present in a left/right symmetrical manner. However, in ref-1 mutants, while the ectopically generated neurons exhibit gene expression profiles characteristic of neurons on the left, they are present only on the right side. REF-1 functions in a Notch-independent manner to regulate this ectopic lineage decision. We also demonstrate that loss of REF-1 function results in defective differentiation of an embryonically generated serotonergic neuron type. These results indicate that REF-1 functions in both Notch-dependent and independent pathways to regulate multiple developmental decisions in different neuronal sublineages.
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Affiliation(s)
- Anne Lanjuin
- Department of Biology, Brandeis University, Waltham, MA 02454, USA
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50
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Peden EM, Barr MM. The KLP-6 kinesin is required for male mating behaviors and polycystin localization in Caenorhabditis elegans. Curr Biol 2005; 15:394-404. [PMID: 15753033 DOI: 10.1016/j.cub.2004.12.073] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2004] [Revised: 12/22/2004] [Accepted: 12/23/2004] [Indexed: 11/28/2022]
Abstract
BACKGROUND Male mating behavior of the nematode Caenorhabditis elegans offers an intriguing model to study the genetics of sensory behavior, cilia function, and autosomal dominant polycystic kidney disease (ADPKD). The C. elegans polycystins LOV-1 and PKD-2 act in male-specific sensory cilia required for response and vulva-location mating behaviors. RESULTS Here, we identify and characterize a new mating mutant, sy511. sy511 behavioral phenotypes were mapped to a mutation in the klp-6 locus, a gene encoding a member of the kinesin-3 family (previously known as the UNC-104/Kif1A family). KLP-6 has a single homolog of unknown function in vertebrate genomes, including fish, chicken, mouse, rat, and human. We show that KLP-6 expresses exclusively in sensory neurons with exposed ciliated endings and colocalizes with the polycystins in cilia of male-specific neurons. Cilia of klp-6 mutants appear normal, suggesting a defect in sensory neuron function but not development. KLP-6 structure-function analysis reveals that the putative cargo binding domain directs the motor to cilia. Consistent with a motor-cargo association between KLP-6 and the polycystins, klp-6 is required for PKD-2 localization and function within cilia. Genetically, we find klp-6 regulates behavior through polycystin-dependent and -independent pathways. CONCLUSION Multiple ciliary transport pathways dependent on kinesin-II, OSM-3, and KLP-6 may act sequentially to build cilia and localize sensory ciliary membrane proteins such as the polycystins. We propose that KLP-6 and the polycystins function as an evolutionarily conserved ciliary unit. KLP-6 promises new routes to understanding cilia function, behavior, and ADPKD.
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MESH Headings
- Animals
- Base Sequence
- Caenorhabditis elegans
- Caenorhabditis elegans Proteins
- Chromosome Mapping
- Cilia/metabolism
- DNA, Complementary/genetics
- Disease Models, Animal
- Gene Components
- Gene Expression
- Green Fluorescent Proteins
- Kinesins/genetics
- Kinesins/metabolism
- Male
- Membrane Proteins/metabolism
- Models, Biological
- Neurons, Afferent/metabolism
- Polycystic Kidney, Autosomal Dominant/metabolism
- Polycystic Kidney, Autosomal Dominant/physiopathology
- Polymorphism, Single Nucleotide/genetics
- Protein Structure, Tertiary
- Proteins/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Analysis, DNA
- Sexual Behavior, Animal/physiology
- TRPP Cation Channels
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Affiliation(s)
- Erik M Peden
- Molecular and Cellular Pharmacology, School of Pharmacy, University of Wisconsin, 777 Highland Avenue, Madison, WI 53705, USA
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