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Harbin JP, Shen Y, Lin SY, Kemper K, Haag ES, Schwarz EM, Ellis RE. Robust sex determination in the Caenorhabditis nigoni germ line. Genetics 2025; 229:iyae207. [PMID: 39663849 PMCID: PMC12005254 DOI: 10.1093/genetics/iyae207] [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: 09/19/2024] [Revised: 11/06/2024] [Accepted: 11/08/2024] [Indexed: 12/13/2024] Open
Abstract
Sexual characteristics and reproductive systems are dynamic traits in many taxa, but the developmental modifications that allow change and innovation are largely unknown. A leading model for this process is the evolution of self-fertile hermaphrodites from male/female ancestors. However, these studies require direct analysis of sex determination in male/female species, as well as in the hermaphroditic species that are related to them. In Caenorhabditis nematodes, this has only become possible recently, with the discovery of new species. Here, we use gene editing to characterize major sex determination genes in Caenorhabditis nigoni, a sister to the widely studied hermaphroditic species Caenorhabditis briggsae. These 2 species are close enough to mate and form partially fertile hybrids. First, we find that tra-1 functions as the master regulator of sex in C. nigoni, in both the soma and the germ line. Surprisingly, these mutants make only sperm, in contrast to tra-1 mutants in related hermaphroditic species. Moreover, the XX mutants display a unique defect in somatic gonad development that is not seen elsewhere in the genus. Second, the fem-3 gene acts upstream of tra-1 in C. nigoni, and the mutants are females, unlike in the sister species C. briggsae, where they develop as hermaphrodites. This result points to a divergence in the role of fem-3 in the germ line of these species. Third, tra-2 encodes a transmembrane receptor that acts upstream of fem-3 in C. nigoni. Outside of the germ line, tra-2 mutations in all species cause a similar pattern of partial masculinization. However, heterozygosity for tra-2 does not alter germ cell fates in C. nigoni, as it can in sensitized backgrounds of 2 hermaphroditic species of Caenorhabditis. Finally, the epistatic relationships point to a simple, linear germline pathway in which tra-2 regulates fem-3 which regulates tra-1, unlike the more complex relationships seen in hermaphrodite germ cell development. Taking these results together, the regulation of sex determination is more robust and streamlined in the male/female species C. nigoni than in related species that make self-fertile hermaphrodites, a conclusion supported by studies of interspecies hybrids using sex determination mutations. Thus, we infer that the origin of self-fertility not only required mutations that activated the spermatogenesis program in XX germ lines, but prior to these there must have been mutations that decanalized the sex determination process, allowing for subsequent changes to germ cell fates.
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Affiliation(s)
- Jonathan P Harbin
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Sciences, Stratford, NJ 08084, USA
| | - Yongquan Shen
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Sciences, Stratford, NJ 08084, USA
| | - Shin-Yi Lin
- Department of Molecular Biology, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Kevin Kemper
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Sciences, Stratford, NJ 08084, USA
| | - Eric S Haag
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Erich M Schwarz
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Ronald E Ellis
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Sciences, Stratford, NJ 08084, USA
- Department of Molecular Biology, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
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2
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Shen Y, Lin SY, Harbin J, Amin R, Vassalotti A, Romanowski J, Schmidt E, Tierney A, Ellis RE. Rewiring the Sex-Determination Pathway During the Evolution of Self-Fertility. Mol Biol Evol 2024; 41:msae101. [PMID: 38880992 PMCID: PMC11180601 DOI: 10.1093/molbev/msae101] [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: 03/08/2024] [Revised: 05/08/2024] [Accepted: 05/10/2024] [Indexed: 06/18/2024] Open
Abstract
Although evolution is driven by changes in how regulatory pathways control development, we know little about the molecular details underlying these transitions. The TRA-2 domain that mediates contact with TRA-1 is conserved in Caenorhabditis. By comparing the interaction of these proteins in two species, we identified a striking change in how sexual development is controlled. Identical mutations in this domain promote oogenesis in Caenorhabditis elegans but promote spermatogenesis in Caenorhabditis briggsae. Furthermore, the effects of these mutations involve the male-promoting gene fem-3 in C. elegans but are independent of fem-3 in C. briggsae. Finally, reciprocal mutations in these genes show that C. briggsae TRA-2 binds TRA-1 to prevent expression of spermatogenesis regulators. By contrast, in C. elegans TRA-1 sequesters TRA-2 in the germ line, allowing FEM-3 to initiate spermatogenesis. Thus, we propose that the flow of information within the sex determination pathway has switched directions during evolution. This result has important implications for how evolutionary change can occur.
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Affiliation(s)
- Yongquan Shen
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Science, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Shin-Yi Lin
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Science, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Jonathan Harbin
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Science, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Richa Amin
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Science, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Allison Vassalotti
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Science, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Joseph Romanowski
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Science, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Emily Schmidt
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Science, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Alexis Tierney
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Science, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Ronald E Ellis
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Science, Rowan-Virtua School of Osteopathic Medicine, Stratford, NJ 08084, USA
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3
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Ivanova M, Moss EG. Orthologs of the Caenorhabditis elegans heterochronic genes have divergent functions in Caenorhabditis briggsae. Genetics 2023; 225:iyad177. [PMID: 37788363 PMCID: PMC10697817 DOI: 10.1093/genetics/iyad177] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 05/22/2023] [Accepted: 09/14/2023] [Indexed: 10/05/2023] Open
Abstract
The heterochronic genes of Caenorhabditis elegans comprise the best-studied pathway controlling the timing of tissue and organ formation in an animal. To begin to understand the evolution of this pathway and the significance of the relationships among its components, we characterized 11 Caenorhabditis briggsae orthologs of C. elegans heterochronic genes. Using CRISPR/Cas9, we made a variety of alleles and found that several mutant phenotypes differ in significant ways from those of C. elegans. Although most mutant orthologs displayed defects in developmental timing, their phenotypes could differ in which stages were affected, the penetrance and expressivity of the phenotypes, or by having additional pleiotropies that were not obviously connected to developmental timing. However, when examining pairwise epistasis and synergistic relationships, we found those paralleled the known relationships between their C. elegans orthologs, suggesting that the arrangements of these genes in functional modules are conserved, but the modules' relationships to each other and/or to their targets has drifted since the time of the species' last common ancestor. Furthermore, our investigation has revealed a relationship between this pathway to other aspects of the animal's growth and development, including gonad development, which is relevant to both species.
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Affiliation(s)
- Maria Ivanova
- Department of Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering and Sciences, Rowan University, Stratford, NJ 08084, USA
| | - Eric G Moss
- Department of Molecular Biology, Rowan University, Stratford, NJ 08084, USA
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4
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Xie D, Gu B, Liu Y, Ye P, Ma Y, Wen T, Song X, Zhao Z. Efficient targeted recombination with CRISPR/Cas9 in hybrids of Caenorhabditis nematodes with suppressed recombination. BMC Biol 2023; 21:203. [PMID: 37775783 PMCID: PMC10542263 DOI: 10.1186/s12915-023-01704-0] [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: 03/27/2023] [Accepted: 09/18/2023] [Indexed: 10/01/2023] Open
Abstract
BACKGROUND Homology-based recombination (HR) is the cornerstone of genetic mapping. However, a lack of sufficient sequence homology or the presence of a genomic rearrangement prevents HR through crossing, which inhibits genetic mapping in relevant genomic regions. This is particularly true in species hybrids whose genomic sequences are highly divergent along with various genome arrangements, making the mapping of genetic loci, such as hybrid incompatibility (HI) loci, through crossing impractical. We previously mapped tens of HI loci between two nematodes, Caenorhabditis briggsae and C. nigoni, through the repeated backcrossing of GFP-linked C. briggsae fragments into C. nigoni. However, the median introgression size was over 7 Mb, indicating apparent HR suppression and preventing the subsequent cloning of the causative gene underlying a given HI phenotype. Therefore, a robust method that permits recombination independent of sequence homology is desperately desired. RESULTS Here, we report a method of highly efficient targeted recombination (TR) induced by CRISPR/Cas9 with dual guide RNAs (gRNAs), which circumvents the HR suppression in hybrids between the two species. We demonstrated that a single gRNA was able to induce efficient TR between highly homologous sequences only in the F1 hybrids but not in the hybrids that carry a GFP-linked C. briggsae fragment in an otherwise C. nigoni background. We achieved highly efficient TR, regardless of sequence homology or genetic background, when dual gRNAs were used that each specifically targeted one parental chromosome. We further showed that dual gRNAs were able to induce efficient TR within genomic regions that had undergone inversion, in which HR-based recombination was expected to be suppressed, supporting the idea that dual-gRNA-induced TR can be achieved through nonhomology-based end joining between two parental chromosomes. CONCLUSIONS Recombination suppression can be circumvented through CRISPR/Cas9 with dual gRNAs, regardless of sequence homology or the genetic background of the species hybrid. This method is expected to be applicable to other situations in which recombination is suppressed in interspecies or intrapopulation hybrids.
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Affiliation(s)
- Dongying Xie
- Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR, China
| | - Bida Gu
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, USA
| | - Yiqing Liu
- Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR, China
| | - Pohao Ye
- Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR, China
| | - Yiming Ma
- Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR, China
| | - Tongshu Wen
- Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR, China
| | - Xiaoyuan Song
- MOE Key Laboratory of Cellular Dynamics, CAS Key Laboratory of Brain Function and Disease, School of Life Sciences, Division of Life Sciences and Medicine, Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026, Anhui, China
| | - Zhongying Zhao
- Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR, China.
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5
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Maushe D, Ogi V, Divakaran K, Verdecia Mogena AM, Himmighofen PA, Machado RAR, Towbin BD, Ehlers RU, Molina C, Parisod C, Maud Robert CA. Stress tolerance in entomopathogenic nematodes: Engineering superior nematodes for precision agriculture. J Invertebr Pathol 2023:107953. [PMID: 37336478 DOI: 10.1016/j.jip.2023.107953] [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: 03/10/2023] [Revised: 06/13/2023] [Accepted: 06/16/2023] [Indexed: 06/21/2023]
Abstract
Entomopathogenic nematodes (EPNs) are soil-dwelling parasitic roundworms commonly used as biocontrol agents of insect pests in agriculture. EPN dauer juveniles locate and infect a host in which they will grow and multiply until resource depletion. During their free-living stage, EPNs face a series of internal and environmental stresses. Their ability to overcome these challenges is crucial to determine their infection success and survival. In this review, we provide a comprehensive overview of EPN response to stresses associated with starvation, low/elevated temperatures, desiccation, osmotic stress, hypoxia, and ultra-violet light. We further report EPN defense strategies to cope with biotic stressors such as viruses, bacteria, fungi, and predatory insects. By comparing the genetic and biochemical basis of these strategies to the nematode model Caenorhabditis elegans, we provide new avenues and targets to select and engineer precision nematodes adapted to specific field conditions.
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Affiliation(s)
- Dorothy Maushe
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland
| | - Vera Ogi
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland
| | - Keerthi Divakaran
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland
| | | | - Paul Anton Himmighofen
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland
| | - Ricardo A R Machado
- Institute of Biology, University of Neuchâtel, Rue Emile Argand 11, CH-2000 Neuchâtel, Switzerland
| | - Benjamin Daniel Towbin
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
| | - Ralf-Udo Ehlers
- e- nema GmbH, Klausdorfer Str. 28-36, DE-24223 Schwentinental, Germany
| | - Carlos Molina
- e- nema GmbH, Klausdorfer Str. 28-36, DE-24223 Schwentinental, Germany
| | - Christian Parisod
- Department of Biology, University of Fribourg, Chemin du Musée 10, CH-1700 Fribourg, Switzerland
| | - Christelle Aurélie Maud Robert
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland; Oeschger Centre for Climate Change Research, University of Bern, Hochschulstrasse 4, CH-3012 Bern, Switzerland.
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6
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Velayudhan SS, Ellis RE. Functional divergence of orthologous temperature-sensitive mutations in C. elegans and C. briggsae. MICROPUBLICATION BIOLOGY 2022; 2022:10.17912/micropub.biology.000705. [PMID: 36575738 PMCID: PMC9790080 DOI: 10.17912/micropub.biology.000705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 01/01/1970] [Accepted: 12/09/2022] [Indexed: 12/29/2022]
Abstract
To learn if orthologous mutations are temperature-sensitive in related species, we studied four C. briggsae mutations orthologous to alleles of important C. elegans genes. Both Cel-glp-4(bn2) and Cbr-glp-4(v473) are temperature-sensitive, causing sterility at 25°C. By contrast, Cel-fog-1 ( q253) is strongly ts , but its ortholog Cbr-fog-1(v442) causes a loss-of-function at all temperatures. Finally, the C. elegans glp-1 alleles bn18 and e2141 are ts sterile. However, their C. briggsae orthologs, Cbr-glp-1(v429) and Cbr-glp-1(v438) respectively, are wild-type at all temperatures. Thus, a ts mutation in one species provides clues about how to design ts alleles in another, but all theoretical outcomes are possible.
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Affiliation(s)
| | - Ronald E Ellis
- Rowan University SOM
,
Correspondence to: Ronald E Ellis (
)
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7
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Delattre M, Goehring NW. The first steps in the life of a worm: Themes and variations in asymmetric division in C. elegans and other nematodes. Curr Top Dev Biol 2021; 144:269-308. [PMID: 33992156 DOI: 10.1016/bs.ctdb.2020.12.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Starting with Boveri in the 1870s, microscopic investigation of early embryogenesis in a broad swath of nematode species revealed the central role of asymmetric cell division in embryonic axis specification, blastomere positioning, and cell fate specification. Notably, across the class Chromadorea, a conserved theme emerges-asymmetry is first established in the zygote and specifies its asymmetric division, giving rise to an anterior somatic daughter cell and a posterior germline daughter cell. Beginning in the 1980s, the emergence of Caenorhabditis elegans as a model organism saw the advent of genetic tools that enabled rapid progress in our understanding of the molecular mechanisms underlying asymmetric division, in many cases defining key paradigms that turn out to regulate asymmetric division in a wide range of systems. Yet, the consequence of this focus on C. elegans came at the expense of exploring the extant diversity of developmental variation exhibited across nematode species. Given the resurgent interest in evolutionary studies facilitated in part by new tools, here we revisit the diversity in this asymmetric first division, juxtaposing molecular insight into mechanisms of symmetry-breaking, spindle positioning and fate specification, with a consideration of plasticity and variability within and between species. In the process, we hope to highlight questions of evolutionary forces and molecular variation that may have shaped the extant diversity of developmental mechanisms observed across Nematoda.
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Affiliation(s)
- Marie Delattre
- Laboratory of Biology and Modeling of the Cell, Ecole Normale Supérieure de Lyon, CNRS, Inserm, UCBL, Lyon, France.
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8
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Culp E, Richman C, Sharanya D, Jhaveri N, van den Berg W, Gupta BP. Genome editing in the nematode Caenorhabditis briggsae using the CRISPR/Cas9 system. Biol Methods Protoc 2020; 5:bpaa003. [PMID: 32395632 PMCID: PMC7200835 DOI: 10.1093/biomethods/bpaa003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 01/27/2020] [Accepted: 02/07/2020] [Indexed: 12/26/2022] Open
Abstract
The CRISPR/Cas system has recently emerged as a powerful tool to engineer the genome of an organism. The system is adopted from bacteria where it confers immunity against invading foreign DNA. This work reports the first successful use of the CRISPR/Cas system in Caenorhabditis briggsae (a cousin of the well-known nematode C. elegans), to generate mutations via non-homologous end joining. We recovered deletion alleles of several conserved genes by microinjecting plasmids that express Cas9 endonuclease and an engineered CRISPR RNA corresponding to the DNA sequence to be cleaved. Evidence for somatic mutations and off-target mutations are also reported. Our approach allows for the generation of loss-of-function mutations in C. briggsae genes thereby facilitating a comparative study of gene function.
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Affiliation(s)
- Elizabeth Culp
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S-4K1, Canada
| | - Cory Richman
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S-4K1, Canada
| | - Devika Sharanya
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S-4K1, Canada
| | - Nikita Jhaveri
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S-4K1, Canada
| | - Wouter van den Berg
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S-4K1, Canada
| | - Bhagwati P Gupta
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S-4K1, Canada
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9
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Booth LN, Maures TJ, Yeo RW, Tantilert C, Brunet A. Self-sperm induce resistance to the detrimental effects of sexual encounters with males in hermaphroditic nematodes. eLife 2019; 8:46418. [PMID: 31282863 PMCID: PMC6697445 DOI: 10.7554/elife.46418] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 07/02/2019] [Indexed: 12/19/2022] Open
Abstract
Sexual interactions have a potent influence on health in several species, including mammals. Previous work in C. elegans identified strategies used by males to accelerate the demise of the opposite sex (hermaphrodites). But whether hermaphrodites evolved counter-strategies against males remains unknown. Here we discover that young C. elegans hermaphrodites are remarkably resistant to brief sexual encounters with males, whereas older hermaphrodites succumb prematurely. Surprisingly, it is not their youthfulness that protects young hermaphrodites, but the fact that they have self-sperm. The beneficial effect of self-sperm is mediated by a sperm-sensing pathway acting on the soma rather than by fertilization. Activation of this pathway in females triggers protection from the negative impact of males. Interestingly, the role of self-sperm in protecting against the detrimental effects of males evolved independently in hermaphroditic nematodes. Endogenous strategies to delay the negative effect of mating may represent a key evolutionary innovation to maximize reproductive success. A nematode worm known as Caenorhabditis elegans is often used in the laboratory to study how animals grow and develop. There are two types of C. elegans worm: hermaphrodite individuals produce both female sex cells (eggs) and male sex cells (sperm), while male individuals only produce sperm. The hermaphrodite worms are able to reproduce without mating with another worm, allowing populations of C. elegans to grow rapidly when they are living in favorable conditions. However, when the hermaphrodites do mate with males they tend to produce more offspring. These offspring are also usually healthier because they receive a mixture of genetic material from two different parents. Although mating is beneficial for the survival of a species it can also harm an individual animal. Previous studies have shown that mating with male worms can accelerate aging of hermaphrodite worms and cause premature death. However, it remained unclear whether hermaphrodite worms have evolved any mechanisms to protect themselves after mating with a male. To address this question, Booth et al. used genetic techniques to study the lifespans of hermaphrodite worms. The experiments found that the hermaphrodites’ own sperm (known as self-sperm) regulated a sperm-sensing signaling pathway that protected them from the negative impact of mating with males. Hermaphrodites with self-sperm that mated with males lived for a similar length of time as hermaphrodites that did not mate. On the other hand, hermaphrodites that did not have self-sperm (because they were older or had a genetic mutation) had shorter lifespans after mating than worms that did not mate. Modulating the sperm-sensing signaling pathway in worms that lacked self-sperm was sufficient to protect them from the negative effects of mating with males. Further experiments found that the hermaphrodites of another nematode worm called C. briggsae – which evolved self-sperm independently of C. elegans – also protected themselves from the negative effects of mating with males in a similar way. This suggests that other animals may also have evolved similar mechanisms to protect themselves from harm when mating. A separate study by Shi et al. has found that the beneficial effects of self-sperm are mediated by a pathway linked to longevity that also exists in mammals. The results of both investigations combined suggest possible avenues for future research into the complex relationship between health, longevity, and reproduction.
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Affiliation(s)
- Lauren N Booth
- Department of Genetics, Stanford University, Stanford, United States
| | - Travis J Maures
- Department of Genetics, Stanford University, Stanford, United States
| | - Robin W Yeo
- Department of Genetics, Stanford University, Stanford, United States
| | - Cindy Tantilert
- Department of Genetics, Stanford University, Stanford, United States
| | - Anne Brunet
- Department of Genetics, Stanford University, Stanford, United States.,Glenn Laboratories for the Biology of Aging at Stanford University, Stanford, United States
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10
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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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11
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Zhao Y, Tan CH, Krauchunas A, Scharf A, Dietrich N, Warnhoff K, Yuan Z, Druzhinina M, Gu SG, Miao L, Singson A, Ellis RE, Kornfeld K. The zinc transporter ZIPT-7.1 regulates sperm activation in nematodes. PLoS Biol 2018; 16:e2005069. [PMID: 29879108 PMCID: PMC5991658 DOI: 10.1371/journal.pbio.2005069] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 04/24/2018] [Indexed: 02/06/2023] Open
Abstract
Sperm activation is a fascinating example of cell differentiation, in which immotile spermatids undergo a rapid and dramatic transition to become mature, motile sperm. Because the sperm nucleus is transcriptionally silent, this transition does not involve transcriptional changes. Although Caenorhabditis elegans is a leading model for studies of sperm activation, the mechanisms by which signaling pathways induce this transformation remain poorly characterized. Here we show that a conserved transmembrane zinc transporter, ZIPT-7.1, regulates the induction of sperm activation in Caenorhabditis nematodes. The zipt-7.1 mutant hermaphrodites cannot self-fertilize, and males reproduce poorly, because mutant spermatids are defective in responding to activating signals. The zipt-7.1 gene is expressed in the germ line and functions in germ cells to promote sperm activation. When expressed in mammalian cells, ZIPT-7.1 mediates zinc transport with high specificity and is predominantly located on internal membranes. Finally, genetic epistasis places zipt-7.1 at the end of the spe-8 sperm activation pathway, and ZIPT-7.1 binds SPE-4, a presenilin that regulates sperm activation. Based on these results, we propose a new model for sperm activation. In spermatids, inactive ZIPT-7.1 is localized to the membranous organelles, which contain higher levels of zinc than the cytoplasm. When sperm activation is triggered, ZIPT-7.1 activity increases, releasing zinc from internal stores. The resulting increase in cytoplasmic zinc promotes the phenotypic changes characteristic of activation. Thus, zinc signaling is a key step in the signal transduction process that mediates sperm activation, and we have identified a zinc transporter that is central to this activation process. Sperm are specialized cells with transcriptionally silent DNA that has been packaged for delivery into the egg. In their final step of development, immature sperm undergo a rapid transition from nonmotile cells to mature, motile sperm capable of fertilization. The signals that trigger this change are not clearly understood. By identifying mutants in the roundworm Caenorhabditis elegans that are defective in sperm activation, we discovered a conserved transmembrane protein, ZIPT-7.1, that transports zinc and promotes sperm activation in both sexes. ZIPT-7.1 is expressed in the germ line and functions there to control sperm activation. When expressed ectopically in mammalian cells, the protein specifically transports zinc across membranes and localizes primarily to membranes within the cell. Previous genetic studies had identified two pathways that mediate sperm activation in C. elegans, and our results suggest that zipt-7.1 acts at the end of one of these two, the spe-8 pathway. We propose that when this pathway triggers sperm activation, it acts through ZIPT-7.1, which mediates the release of zinc from internal stores in the immature sperm. This released zinc functions as a second messenger to promote the differentiation of mature, motile sperm.
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Affiliation(s)
- Yanmei Zhao
- Key Laboratory of RNA Biology, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
- Department of Molecular Biology, Rowan University SOM, Stratford, New Jersey, United States of America
| | - Chieh-Hsiang Tan
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Amber Krauchunas
- Waksman Institute, Rutgers University, Piscataway, New Jersey, United States of America
| | - Andrea Scharf
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Nicholas Dietrich
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Kurt Warnhoff
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Zhiheng Yuan
- Key Laboratory of RNA Biology, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Marina Druzhinina
- Waksman Institute, Rutgers University, Piscataway, New Jersey, United States of America
| | - Sam Guoping Gu
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
| | - Long Miao
- Key Laboratory of RNA Biology, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Andrew Singson
- Waksman Institute, Rutgers University, Piscataway, New Jersey, United States of America
| | - Ronald E. Ellis
- Department of Molecular Biology, Rowan University SOM, Stratford, New Jersey, United States of America
- * E-mail: (REE); (KK)
| | - Kerry Kornfeld
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail: (REE); (KK)
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12
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Berenson AL, Baird SE. Regulation of the sperm-to-oocyte transition in Caenorhabditis briggsae
hermaphrodites by the Cbr-met-2
and Cbr-fem-3
genes. Mol Reprod Dev 2018; 85:532-542. [DOI: 10.1002/mrd.22991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 04/22/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Aaron L. Berenson
- Department of Biological Sciences; Wright State University; Dayton Ohio
| | - Scott E. Baird
- Department of Biological Sciences; Wright State University; Dayton Ohio
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13
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Revisiting Suppression of Interspecies Hybrid Male Lethality in Caenorhabditis Nematodes. G3-GENES GENOMES GENETICS 2017; 7:1211-1214. [PMID: 28209763 PMCID: PMC5386869 DOI: 10.1534/g3.117.039479] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Within the nematode genus Caenorhabditis, Caenorhabditis briggsae and C. nigoni are among the most closely related species known. They differ in sexual mode, with C. nigoni retaining the ancestral XO male-XX female outcrossing system, while C. briggsae recently evolved self-fertility and an XX-biased sex ratio. Wild-type C. briggsae and C. nigoni can produce fertile hybrid XX female progeny, but XO progeny are either 100% inviable (when C. briggsae is the mother) or viable but sterile (when C. nigoni is the mother). A recent study provided evidence suggesting that loss of the Cbr-him-8 meiotic regulator in C. briggsae hermaphrodites allowed them to produce viable and fertile hybrid XO male progeny when mated to C. nigoni Because such males would be useful for a variety of genetic experiments, we sought to verify this result. Preliminary crosses with wild-type C. briggsae hermaphrodites occasionally produced fertile males, but they could not be confirmed to be interspecies hybrids. Using an RNA interference (RNAi) protocol that eliminates any possibility of self-progeny in Cbr-him-8 hermaphrodites, we found sterile males bearing the C. nigoni X chromosome, but no fertile males bearing the C. briggsae X, as in wild-type crosses. Our results suggest that the apparent rescue of XO hybrid viability and fertility is due to incomplete purging of self-sperm prior to mating.
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14
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Evolution of New cis-Regulatory Motifs Required for Cell-Specific Gene Expression in Caenorhabditis. PLoS Genet 2016; 12:e1006278. [PMID: 27588814 PMCID: PMC5010242 DOI: 10.1371/journal.pgen.1006278] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 08/04/2016] [Indexed: 12/19/2022] Open
Abstract
Patterning of C. elegans vulval cell fates relies on inductive signaling. In this induction event, a single cell, the gonadal anchor cell, secretes LIN-3/EGF and induces three out of six competent precursor cells to acquire a vulval fate. We previously showed that this developmental system is robust to a four-fold variation in lin-3/EGF genetic dose. Here using single-molecule FISH, we find that the mean level of expression of lin-3 in the anchor cell is remarkably conserved. No change in lin-3 expression level could be detected among C. elegans wild isolates and only a low level of change—less than 30%—in the Caenorhabditis genus and in Oscheius tipulae. In C. elegans, lin-3 expression in the anchor cell is known to require three transcription factor binding sites, specifically two E-boxes and a nuclear-hormone-receptor (NHR) binding site. Mutation of any of these three elements in C. elegans results in a dramatic decrease in lin-3 expression. Yet only a single E-box is found in the Drosophilae supergroup of Caenorhabditis species, including C. angaria, while the NHR-binding site likely only evolved at the base of the Elegans group. We find that a transgene from C. angaria bearing a single E-box is sufficient for normal expression in C. elegans. Even a short 58 bp cis-regulatory fragment from C. angaria with this single E-box is able to replace the three transcription factor binding sites at the endogenous C. elegans lin-3 locus, resulting in the wild-type expression level. Thus, regulatory evolution occurring in cis within a 58 bp lin-3 fragment, results in a strict requirement for the NHR binding site and a second E-box in C. elegans. This single-cell, single-molecule, quantitative and functional evo-devo study demonstrates that conserved expression levels can hide extensive change in cis-regulatory site requirements and highlights the evolution of new cis-regulatory elements required for cell-specific gene expression. Diversification of mechanisms regulating gene expression of key developmental factors is a major force in the evolution of development. However, in the past, comparisons of gene expression across different species have often been qualitative (i.e. ‘expression is on versus off’ in a certain cell) without precise quantification. New experimental methods now allow us to quantitatively compare the expression of gene homologs across species, with single cell resolution. Moreover, the development of genome editing tools enables the dissection of regulatory DNA sequences that drive gene expression. We use here a well-established “textbook” example of animal organogenesis in the microscopic nematode, Caenorhabditis elegans, focusing on the expression of lin-3, coding for the main inducer of the vulva, in a single cell called the anchor cell. We find that the lin-3 expression level is remarkably conserved, with 20–25 messenger RNAs per anchor cell, in species that are molecularly as distant as fish and mammals. This conservation occurs despite substantial changes and compensation in the regulatory elements required for cell-specific gene expression.
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15
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Abstract
Classical and reverse genetics remain invaluable tools for the scientific investigation of model organisms. Genetic analysis of endoparasites is generally difficult because the sexual adults required for crossing and other manipulations are usually hidden within their host. Strongyloides spp. and Parastrongyloides spp. are notable exceptions to this and their free-living adults offer unique opportunities to manipulate these parasites experimentally. Here I review the modes of inheritance in the two generations of Strongyloides/Parastrongyloides and I discuss the opportunities and the limitations of the currently available methodology for the genetic analysis of these two genera.
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16
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Genome Editing in C. elegans and Other Nematode Species. Int J Mol Sci 2016; 17:295. [PMID: 26927083 PMCID: PMC4813159 DOI: 10.3390/ijms17030295] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 12/21/2015] [Accepted: 02/15/2016] [Indexed: 02/06/2023] Open
Abstract
Caenorhabditis elegans, a 1 mm long free-living nematode, is a popular model animal that has been widely utilized for genetic investigations of various biological processes. Characteristic features that make C. elegans a powerful model of choice for eukaryotic genetic studies include its rapid life cycle (development from egg to adult in 3.5 days at 20 °C), well-annotated genome, simple morphology (comprising only 959 somatic cells in the hermaphrodite), and transparency (which facilitates non-invasive fluorescence observations). However, early approaches to introducing mutations in the C. elegans genome, such as chemical mutagenesis and imprecise excision of transposons, have required large-scale mutagenesis screens. To avoid this laborious and time-consuming procedure, genome editing technologies have been increasingly used in nematodes including C. briggsae and Pristionchus pacificus, thereby facilitating their genetic analyses. Here, I review the recent progress in genome editing technologies using zinc-finger nucleases (ZFNs), transcriptional activator-like nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 in nematodes and offer perspectives on their use in the future.
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17
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Ragavapuram V, Hill EE, Baird SE. Suppression of F1 Male-Specific Lethality in Caenorhabditis Hybrids by cbr-him-8. G3 (BETHESDA, MD.) 2015; 6:623-9. [PMID: 26721896 PMCID: PMC4777125 DOI: 10.1534/g3.115.025320] [Citation(s) in RCA: 9] [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: 11/24/2015] [Accepted: 12/29/2015] [Indexed: 01/26/2023]
Abstract
Haldane's Rule and Darwin's Corollary to Haldane's Rule are the observations that heterogametic F1 hybrids are frequently less fit than their homogametic siblings, and that asymmetric results are often obtained from reciprocal hybrid crosses. In Caenorhabditis, Haldane's Rule and Darwin's Corollary have been observed in several hybrid crosses, including crosses of Caenorhabditis briggsae and C. nigoni. Fertile F1 females are obtained from reciprocal crosses. However, F1 males obtained from C. nigoni mothers are sterile and F1 males obtained from C. briggsae die during embryogenesis. We have identified cbr-him-8 as a recessive maternal-effect suppressor of F1 hybrid male-specific lethality in this combination of species. This result implicates epigenetic meiotic silencing in the suppression of F1 male-specific lethality. It is also shown that F1 males bearing a C. briggsae X chromosome are fertile. When crossed to C. briggsae hermaphrodites or F1 females derived from C. briggsae hermaphrodites, viable F2 and backcross (B2) progeny were obtained. Sibling males that possessed a C. nigoni X chromosome were sterile. Therefore, the sterility of F1 males bearing a C. nigoni X chromosome must result from dysgenic interactions between the X chromosome of C. nigoni and the autosomes of C. briggsae. The fertility of F1 males bearing a C. briggsae X chromosome provides an opportunity to identify C. nigoni loci that prevent spermatogenesis, and hence hermaphroditic reproduction, in diplo-X hybrids.
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Affiliation(s)
| | - Emily Elaine Hill
- Department of Biological Sciences, Wright State University, Dayton, Ohio 45435
| | - Scott Everet Baird
- Department of Biological Sciences, Wright State University, Dayton, Ohio 45435
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18
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Ward JD. Rendering the Intractable More Tractable: Tools from Caenorhabditis elegans Ripe for Import into Parasitic Nematodes. Genetics 2015; 201:1279-94. [PMID: 26644478 PMCID: PMC4676526 DOI: 10.1534/genetics.115.182717] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 10/20/2015] [Indexed: 12/14/2022] Open
Abstract
Recent and rapid advances in genetic and molecular tools have brought spectacular tractability to Caenorhabditis elegans, a model that was initially prized because of its simple design and ease of imaging. C. elegans has long been a powerful model in biomedical research, and tools such as RNAi and the CRISPR/Cas9 system allow facile knockdown of genes and genome editing, respectively. These developments have created an additional opportunity to tackle one of the most debilitating burdens on global health and food security: parasitic nematodes. I review how development of nonparasitic nematodes as genetic models informs efforts to import tools into parasitic nematodes. Current tools in three commonly studied parasites (Strongyloides spp., Brugia malayi, and Ascaris suum) are described, as are tools from C. elegans that are ripe for adaptation and the benefits and barriers to doing so. These tools will enable dissection of a huge array of questions that have been all but completely impenetrable to date, allowing investigation into host-parasite and parasite-vector interactions, and the genetic basis of parasitism.
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Affiliation(s)
- Jordan D Ward
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94158
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19
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Sharanya D, Fillis CJ, Kim J, Zitnik EM, Ward KA, Gallagher ME, Chamberlin HM, Gupta BP. Mutations in Caenorhabditis briggsae identify new genes important for limiting the response to EGF signaling during vulval development. Evol Dev 2015; 17:34-48. [PMID: 25627712 DOI: 10.1111/ede.12105] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Studies of vulval development in the nematode C. elegans have identified many genes that are involved in cell division and differentiation processes. Some of these encode components of conserved signal transduction pathways mediated by EGF, Notch, and Wnt. To understand how developmental mechanisms change during evolution, we are doing a comparative analysis of vulva formation in C. briggsae, a species that is closely related to C. elegans. Here, we report 14 mutations in 7 Multivulva (Muv) genes in C. briggsae that inhibit inappropriate division of vulval precursors. We have developed a new efficient and cost-effective gene mapping method to localize Muv mutations to small genetic intervals on chromosomes, thus facilitating cloning and functional studies. We demonstrate the utility of our method by determining molecular identities of three of the Muv genes that include orthologs of Cel-lin-1 (ETS) and Cel-lin-31 (Winged-Helix) of the EGF-Ras pathway and Cel-pry-1 (Axin), of the Wnt pathway. The remaining four genes reside in regions that lack orthologs of known C. elegans Muv genes. Inhibitor studies demonstrate that the Muv phenotype of all four new genes is dependent on the activity of the EGF pathway kinase, MEK. One of these, Cbr-lin(gu167), shows modest increase in the expression of Cbr-lin-3/EGF compared to wild type. These results argue that while Cbr-lin(gu167) may act upstream of Cbr-lin-3/EGF, the other three genes influence the EGF pathway downstream or in parallel to Cbr-lin-3. Overall, our findings demonstrate that the genetic program underlying a conserved developmental process includes both conserved and divergent functional contributions.
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Affiliation(s)
- Devika Sharanya
- Department of Biology, McMaster University, Hamilton, ON, Canada
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20
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Co-option of alternate sperm activation programs in the evolution of self-fertile nematodes. Nat Commun 2014; 5:5888. [PMID: 25523309 DOI: 10.1038/ncomms6888] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Accepted: 11/18/2014] [Indexed: 12/19/2022] Open
Abstract
Self-fertility evolved independently in three species of Caenorhabditis, yet the underlying genetic changes remain unclear. This transition required that XX animals acquire the ability to produce sperm and then signal those sperm to activate and fertilise oocytes. Here, we show that all genes that regulate sperm activation in C. elegans are conserved throughout the genus, even in male/female species. By using gene editing, we show that C. elegans and C. briggsae hermaphrodites use the SPE-8 tyrosine kinase pathway to activate sperm, whereas C. tropicalis hermaphrodites use a TRY-5 serine protease pathway. Finally, our analysis of double mutants shows that these pathways were redundant in ancestral males. Thus, newly evolving hermaphrodites became self-fertile by co-opting either of the two redundant male programs. The existence of these alternatives helps explain the frequent origin of self-fertility in nematode lineages. This work also demonstrates that the new genome-editing techniques allow unprecedented power and precision in evolutionary studies.
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21
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Ellis RE, Lin SY. The evolutionary origins and consequences of self-fertility in nematodes. F1000PRIME REPORTS 2014; 6:62. [PMID: 25165561 PMCID: PMC4126538 DOI: 10.12703/p6-62] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Self-fertile hermaphrodites have evolved from male/female ancestors in many nematode species, and this transition occurred on three independent occasions in the genus Caenorhabditis. Genetic analyses in Caenorhabditis show that the origin of hermaphrodites required two types of changes: alterations to the sex-determination pathway that allowed otherwise female animals to make sperm during larval development, and the production of signals from the gonad that caused these sperm to activate and fertilize oocytes. Comparisons of C. elegans and C. briggsae hermaphrodites show that the ancestral sex-determination pathway has been altered in multiple unique ways. Some of these changes must have precipitated the production of sperm in XX animals, and others were modifying mutations that increased the efficiency of hermaphroditic reproduction. Reverse genetic experiments show that XX animals acquired the ability to activate sperm by co-opting one of the two redundant pathways that normally work in males. Finally, the adoption of a hermaphroditic lifestyle had profound effects on ecological and sexual interactions and genomic organization. Thus, nematode mating systems are ideal for elucidating the origin of novel traits, and studying the influence of developmental processes on evolutionary change.
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22
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Chen X, Shen Y, Ellis RE. Dependence of the sperm/oocyte decision on the nucleosome remodeling factor complex was acquired during recent Caenorhabditis briggsae evolution. Mol Biol Evol 2014; 31:2573-85. [PMID: 24987105 PMCID: PMC4166919 DOI: 10.1093/molbev/msu198] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The major families of chromatin remodelers have been conserved throughout eukaryotic evolution. Because they play broad, pleiotropic roles in gene regulation, it was not known if their functions could change rapidly. Here, we show that major alterations in the use of chromatin remodelers are possible, because the nucleosome remodeling factor (NURF) complex has acquired a unique role in the sperm/oocyte decision of the nematode Caenorhabditis briggsae. First, lowering the activity of C. briggsae NURF-1 or ISW-1, the core components of the NURF complex, causes germ cells to become oocytes rather than sperm. This observation is based on the analysis of weak alleles and null mutations that were induced with TALENs and on RNA interference. Second, qRT-polymerase chain reaction data show that the C. briggsae NURF complex promotes the expression of Cbr-fog-1 and Cbr-fog-3, two genes that control the sperm/oocyte decision. This regulation occurs in the third larval stage and affects the expression of later spermatogenesis genes. Third, double mutants reveal that the NURF complex and the transcription factor TRA-1 act independently on Cbr-fog-1 and Cbr-fog-3. TRA-1 binds both promoters, and computer analyses predict that these binding sites are buried in nucleosomes, so we suggest that the NURF complex alters chromatin structure to allow TRA-1 access to Cbr-fog-1 and Cbr-fog-3. Finally, lowering NURF activity by mutation or RNA interference does not affect this trait in other nematodes, including the sister species C. nigoni, so it must have evolved recently. We conclude that altered chromatin remodeling could play an important role in evolutionary change.
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Affiliation(s)
- Xiangmei Chen
- Department of Molecular Biology, Rowan University-SOM Graduate School of Biomedical Sciences, University of Medicine and Dentistry of New Jersey
| | - Yongquan Shen
- Department of Molecular Biology, Rowan University-SOM
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23
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Abstract
Intense reproductive competition often continues long after animals finish mating. In many species, sperm from one male compete with those from others to find and fertilize oocytes. Since this competition occurs inside the female reproductive tract, she often influences the outcome through physical or chemical factors, leading to cryptic female choice. Finally, traits that help males compete with each other are sometimes harmful to females, and female countermeasures may thwart the interests of males, which can lead to an arms race between the sexes known as sexually antagonistic coevolution. New studies from Caenorhabditis nematodes suggest that males compete with each other by producing sperm that migrate aggressively and that these sperm may be more likely to win access to oocytes. However, one byproduct of this competition appears to be an increased probability that these sperm will go astray, invading the ovary, prematurely activating oocytes, and sometimes crossing basement membranes and leaving the gonad altogether. These harmful effects are sometimes observed in crosses between animals of the same species but are most easily detected in interspecies crosses, leading to dramatically lowered fitness, presumably because the competitiveness of the sperm and the associated female countermeasures are not precisely matched. This mismatch is most obvious in crosses involving individuals from androdioecious species (which have both hermaphrodites and males), as predicted by the lower levels of sperm competition these species experience. These results suggest a striking example of sexually antagonistic coevolution and dramatically expand the value of nematodes as a laboratory system for studying postcopulatory interactions.
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Affiliation(s)
- Ronald E. Ellis
- Department of Molecular Biology, Rowan University SOM, Stratford, New Jersey, United States of America
| | - Lukas Schärer
- Evolutionary Biology, Zoological Institute, University of Basel, Basel, Switzerland
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24
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Ellis RE, Stanfield GM. The regulation of spermatogenesis and sperm function in nematodes. Semin Cell Dev Biol 2014; 29:17-30. [PMID: 24718317 PMCID: PMC4082717 DOI: 10.1016/j.semcdb.2014.04.005] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 04/01/2014] [Indexed: 12/12/2022]
Abstract
In the nematode C. elegans, both males and self-fertile hermaphrodites produce sperm. As a result, researchers have been able to use a broad range of genetic and genomic techniques to dissect all aspects of sperm development and function. Their results show that the early stages of spermatogenesis are controlled by transcriptional and translational processes, but later stages are dominated by protein kinases and phosphatases. Once spermatids are produced, they participate in many interactions with other cells - signals from the somatic gonad determine when sperm activate and begin to crawl, signals from the female reproductive tissues guide the sperm, and signals from sperm stimulate oocytes to mature and be ovulated. The sperm also show strong competitive interactions with other sperm and oocytes. Some of the molecules that mediate these processes have conserved functions in animal sperm, others are conserved proteins that have been adapted for new roles in nematode sperm, and some are novel proteins that provide insights into evolutionary change. The advent of new techniques should keep this system on the cutting edge of research in cellular and reproductive biology.
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Affiliation(s)
- Ronald E Ellis
- Department of Molecular Biology, Rowan University SOM, B303 Science Center, 2 Medical Center Drive, Stratford, NJ 08084, United States.
| | - Gillian M Stanfield
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, United States
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