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Behrens KA, Koblmüller S, Kocher TD. Genome assemblies for Chromidotilapia guntheri (Teleostei: Cichlidae) identify a novel candidate gene for vertebrate sex determination, RIN3. Front Genet 2024; 15:1447628. [PMID: 39221227 PMCID: PMC11361979 DOI: 10.3389/fgene.2024.1447628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Accepted: 08/06/2024] [Indexed: 09/04/2024] Open
Abstract
Advances in genome sequencing have greatly accelerated the identification of sex chromosomes in a variety of species. Many of these species have experienced structural rearrangements that reduce recombination between the sex chromosomes, allowing the accumulation of sequence differences over many megabases. Identification of the genes that are responsible for sex determination within these sometimes large regions has proved difficult. Here, we identify an XY sex chromosome system on LG19 in the West African cichlid fish Chromidotilapia guntheri in which the region of differentiation extends over less than 400 kb. We develop high-quality male and female genome assemblies for this species, which confirm the absence of structural variants, and which facilitate the annotation of genes in the region. The peak of differentiation lies within rin3, which has experienced several debilitating mutations on the Y chromosome. We suggest two hypotheses about how these mutations might disrupt endocytosis, leading to Mendelian effects on sexual development.
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Affiliation(s)
- Kristen A. Behrens
- Department of Biology, University of Maryland, College Park, MD, United States
| | | | - Thomas D. Kocher
- Department of Biology, University of Maryland, College Park, MD, United States
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Behrens KA, Koblmueller S, Kocher TD. Diversity of Sex Chromosomes in Vertebrates: Six Novel Sex Chromosomes in Basal Haplochromines (Teleostei: Cichlidae). Genome Biol Evol 2024; 16:evae152. [PMID: 39073759 DOI: 10.1093/gbe/evae152] [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] [Accepted: 07/12/2024] [Indexed: 07/30/2024] Open
Abstract
African cichlid fishes are known for their high rates of phenotypic evolution. A rapid rate of diversification is apparent also in the diversity of their sex chromosomes. To date, sex determiners have been identified on 18 of 22 chromosomes in the standard karyotype. Here, we use whole-genome sequencing to characterize the sex chromosomes of seven populations of basal haplochromines, focusing on the genus Pseudocrenilabrus. We identify six new sex chromosome systems, including the first report of a cichlid sex-determining system on linkage group 12. We then quantify the rates and patterns of sex chromosome turnover in this clade. Finally, we test whether some autosomes become sex chromosomes in East African cichlids more often than expected by chance.
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Affiliation(s)
- Kristen A Behrens
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | | | - Thomas D Kocher
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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Behrens KA, Zimmermann H, Blažek R, Reichard M, Koblmüller S, Kocher TD. Turnover of sex chromosomes in the Lake Tanganyika cichlid tribe Tropheini (Teleostei: Cichlidae). Sci Rep 2024; 14:2471. [PMID: 38291228 PMCID: PMC10828463 DOI: 10.1038/s41598-024-53021-3] [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: 07/14/2023] [Accepted: 01/25/2024] [Indexed: 02/01/2024] Open
Abstract
Sex chromosome replacement is frequent in many vertebrate clades, including fish, frogs, and lizards. In order to understand the mechanisms responsible for sex chromosome turnover and the early stages of sex chromosome divergence, it is necessary to study lineages with recently evolved sex chromosomes. Here we examine sex chromosome evolution in a group of African cichlid fishes (tribe Tropheini) which began to diverge from one another less than 4 MYA. We have evidence for a previously unknown sex chromosome system, and preliminary indications of several additional systems not previously reported in this group. We find a high frequency of sex chromosome turnover and estimate a minimum of 14 turnovers in this tribe. We date the origin of the most common sex determining system in this tribe (XY-LG5/19) near the base of one of two major sub-clades of this tribe, about 3.4 MY ago. Finally, we observe variation in the size of one sex-determining region that suggests independent evolution of evolutionary strata in species with a shared sex-determination system. Our results illuminate the rapid rate of sex chromosome turnover in the tribe Tropheini and set the stage for further studies of the dynamics of sex chromosome evolution in this group.
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Affiliation(s)
- Kristen A Behrens
- Department of Biology, University of Maryland, College Park, MD, 20742, USA.
| | - Holger Zimmermann
- Institute of Vertebrate Biology, Czech Academy of Sciences, Květná 8, 603 00, Brno, Czech Republic
- Institute of Biology, University of Graz, Universitätsplatz 2, 8010, Graz, Austria
| | - Radim Blažek
- Institute of Vertebrate Biology, Czech Academy of Sciences, Květná 8, 603 00, Brno, Czech Republic
| | - Martin Reichard
- Institute of Vertebrate Biology, Czech Academy of Sciences, Květná 8, 603 00, Brno, Czech Republic
- Department of Ecology and Vertebrate Zoology, University of Łódź, Łódź, Poland
| | - Stephan Koblmüller
- Institute of Biology, University of Graz, Universitätsplatz 2, 8010, Graz, Austria
| | - Thomas D Kocher
- Department of Biology, University of Maryland, College Park, MD, 20742, USA
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