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Bertho S, Herpin A, Jouanno E, Yano A, Bobe J, Parrinello H, Journot L, Guyomard R, Muller T, Swanson P, McKinney G, Williamson K, Meek M, Schartl M, Guiguen Y. A nonfunctional copy of the salmonid sex-determining gene ( sdY) is responsible for the “apparent” XY females in Chinook salmon, Oncorhynchus tshawytscha. G3 GENES|GENOMES|GENETICS 2022; 12:6493265. [PMID: 35100376 PMCID: PMC8824802 DOI: 10.1093/g3journal/jkab451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 12/03/2021] [Indexed: 11/14/2022]
Abstract
Abstract
Many salmonids have a male heterogametic (XX/XY) sex determination system, and they are supposed to have a conserved master sex-determining gene (sdY) that interacts at the protein level with Foxl2 leading to the blockage of the synergistic induction of Foxl2 and Nr5a1 of the cyp19a1a promoter. However, this hypothesis of a conserved master sex-determining role of sdY in salmonids is challenged by a few exceptions, one of them being the presence of naturally occurring “apparent” XY Chinook salmon, Oncorhynchus tshawytscha, females. Here, we show that some XY Chinook salmon females have a sdY gene (sdY-N183), with 1 missense mutation leading to a substitution of a conserved isoleucine to an asparagine (I183N). In contrast, Chinook salmon males have both a nonmutated sdY-I183 gene and the missense mutation sdY-N183 gene. The 3-dimensional model of SdY-I183N predicts that the I183N hydrophobic to hydrophilic amino acid change leads to a modification in the SdY β-sandwich structure. Using in vitro cell transfection assays, we found that SdY-I183N, like the wild-type SdY, is preferentially localized in the cytoplasm. However, compared to wild-type SdY, SdY-I183N is more prone to degradation, its nuclear translocation by Foxl2 is reduced, and SdY-I183N is unable to significantly repress the synergistic Foxl2/Nr5a1 induction of the cyp19a1a promoter. Altogether, our results suggest that the sdY-N183 gene of XY Chinook females is nonfunctional and that SdY-I183N is no longer able to promote testicular differentiation by impairing the synthesis of estrogens in the early differentiating gonads of wild Chinook salmon XY females.
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Affiliation(s)
- Sylvain Bertho
- INRAE, LPGP, Rennes 35000, France
- Physiological Chemistry, Biocenter, University of Wuerzburg, Wuerzburg 97074, Germany
| | | | | | | | | | - Hugues Parrinello
- Institut de Génomique Fonctionnelle, IGF, CNRS, INSERM, Univ. Montpellier, Montpellier 34094, France
| | - Laurent Journot
- Institut de Génomique Fonctionnelle, IGF, CNRS, INSERM, Univ. Montpellier, Montpellier 34094, France
| | - René Guyomard
- GABI, INRAE, AgroParisTech, Université Paris-Saclay, Paris 75005, France
| | - Thomas Muller
- Julius-von-Sachs-Institute, Department of Molecular Plant Physiology and Biophysics, University of Wuerzburg, Wuerzburg 97082, Germany
| | - Penny Swanson
- Environmental and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, WA 98112, USA
| | - Garrett McKinney
- Molecular Genetics Laboratory, Washington Department of Fish & Wildlife, Olympia, WA 98501, USA
| | | | - Mariah Meek
- Dept. of Integrative Biology, AgBio Research, and Ecology, Evolution, and Behavior Program, Michigan State University, East Lansing, MI 48824, USA
| | - Manfred Schartl
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX 78666, USA
- Department of Developmental Biochemistry, Biocenter, University of Wüerzburg, Wuerzburg 97074, Germany
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Bertho S, Herpin A, Schartl M, Guiguen Y. Lessons from an unusual vertebrate sex-determining gene. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200092. [PMID: 34247499 DOI: 10.1098/rstb.2020.0092] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
So far, very few sex-determining genes have been identified in vertebrates and most of them, the so-called 'usual suspects', evolved from genes which fulfil essential functions during sexual development and are thus already tightly linked to the process that they now govern. The single exception to this 'usual suspects' rule in vertebrates so far is the conserved salmonid sex-determining gene, sdY (sexually dimorphic on the Y chromosome), that evolved from a gene known to be involved in regulation of the immune response. It is contained in a jumping sex locus that has been transposed or translocated into different ancestral autosomes during the evolution of salmonids. This special feature of sdY, i.e. being inserted in a 'jumping sex locus', could explain how salmonid sex chromosomes remain young and undifferentiated to escape degeneration. Recent knowledge on the mechanism of action of sdY demonstrates that it triggers its sex-determining action by deregulating oestrogen synthesis that is a conserved and crucial pathway for ovarian differentiation in vertebrates. This result suggests that sdY has evolved to cope with a pre-existing sex differentiation regulatory network. Therefore, 'limited options' for the emergence of new master sex-determining genes could be more constrained by their need to tightly interact with a conserved sex differentiation regulatory network rather than by being themselves 'usual suspects', already inside this sex regulatory network. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)'.
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Affiliation(s)
- Sylvain Bertho
- INRAE, LPGP, 35000 Rennes, France.,Developmental Biochemistry, Biocenter, University of Wuerzburg, 97074 Wuerzburg, Germany
| | - Amaury Herpin
- INRAE, LPGP, 35000 Rennes, France.,State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Sciences, Hunan Normal University, Changsha, 410081 Hunan, People's Republic of China
| | - Manfred Schartl
- Developmental Biochemistry, Biocenter, University of Wuerzburg, 97074 Wuerzburg, Germany.,Department of Chemistry and Biochemistry, The Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX 78666, USA
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The sockeye salmon genome, transcriptome, and analyses identifying population defining regions of the genome. PLoS One 2020; 15:e0240935. [PMID: 33119641 PMCID: PMC7595290 DOI: 10.1371/journal.pone.0240935] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 10/06/2020] [Indexed: 12/12/2022] Open
Abstract
Sockeye salmon (Oncorhynchus nerka) is a commercially and culturally important species to the people that live along the northern Pacific Ocean coast. There are two main sockeye salmon ecotypes—the ocean-going (anadromous) ecotype and the fresh-water ecotype known as kokanee. The goal of this study was to better understand the population structure of sockeye salmon and identify possible genomic differences among populations and between the two ecotypes. In pursuit of this goal, we generated the first reference sockeye salmon genome assembly and an RNA-seq transcriptome data set to better annotate features of the assembly. Resequenced whole-genomes of 140 sockeye salmon and kokanee were analyzed to understand population structure and identify genomic differences between ecotypes. Three distinct geographic and genetic groups were identified from analyses of the resequencing data. Nucleotide variants in an immunoglobulin heavy chain variable gene cluster on chromosome 26 were found to differentiate the northwestern group from the southern and upper Columbia River groups. Several candidate genes were found to be associated with the kokanee ecotype. Many of these genes were related to ammonia tolerance or vision. Finally, the sex chromosomes of this species were better characterized, and an alternative sex-determination mechanism was identified in a subset of upper Columbia River kokanee.
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Ayllon F, Solberg MF, Besnier F, Fjelldal PG, Hansen TJ, Wargelius A, Edvardsen RB, Glover KA. Autosomal sdY Pseudogenes Explain Discordances Between Phenotypic Sex and DNA Marker for Sex Identification in Atlantic Salmon. Front Genet 2020; 11:544207. [PMID: 33173531 PMCID: PMC7591749 DOI: 10.3389/fgene.2020.544207] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 09/17/2020] [Indexed: 11/13/2022] Open
Abstract
Despite the key role that sex-determination plays in evolutionary processes, it is still poorly understood in many species. In salmonids, which are among the best studied fishes, the master sex-determining gene sexually dimorphic on the Y-chromosome (sdY) has been identified. However, sdY displays unexplained discordance to the phenotypic sex, with a variable frequency of phenotypic females being reported as genetic males. Multiple sex determining loci in Atlantic salmon have also been reported, possibly as a result of recent transposition events in this species. We hypothesized the existence of an autosomal copy of sdY, causing apparent discordance between phenotypic and genetic sex, that is transmitted in accordance with autosomal inheritance. To test this, we developed a qPCR methodology to detect the total number of sdY copies present in the genome. Based on the observed phenotype/genotype frequencies and linkage analysis among 2,025 offspring from 64 pedigree-controlled families of accurately phenotyped Atlantic salmon, we identified both males and females carrying one or two autosomal copies of sdY in addition to the Y-specific copy present in males. Patterns across families were highly consistent with autosomal inheritance. These autosomal sdY copies appear to have lost the ability to function as a sex determining gene and were only occasionally assigned to the actual sex chromosome in any of the affected families.
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Affiliation(s)
| | | | | | | | | | | | | | - Kevin Alan Glover
- Institute of Marine Research, Bergen, Norway.,Department of Biological Sciences, University of Bergen, Bergen, Norway
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