Is a Sex-Determining Gene(s) Necessary for Sex-Determination in Amphibians? Steroid Hormones May Be the Key Factor

Nakamura, Masahisa

doi:10.1159/000339661

Cited by 42 publications

(40 citation statements)

References 117 publications

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“…Mutations of CYP17A1 in humans produce low androgen levels and ambiguous or female external genitalia in XY individuals [47]. In amphibians ( Rana frogs), CYP17 has been repeatedly implicated as one of the key players in gonadal differentiation [48]. In the cichlid Nile tilapia, strong sexually dimorphic expression of cyp17a1 is found during sexual differentiation [49].…”

Section: Resultsmentioning

confidence: 99%

Polygenic sex determination in the cichlid fish Astatotilapia burtoni

et al. 2016

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BackgroundThe East African riverine cichlid species Astatotilapia burtoni serves as an important laboratory model for sexually dimorphic physiology and behavior, and also serves as an outgroup species for the explosive adaptive radiations of cichlid species in Lake Malawi and Lake Victoria. An astounding diversity of genetic sex determination systems have been revealed within the adaptive radiation of East African cichlids thus far, including polygenic sex determination systems involving the epistatic interaction of multiple, independently segregating sex determination alleles. However, sex determination has remained unmapped in A. burtoni. Here we present mapping results supporting the presence of multiple, novel sex determination alleles, and thus the presence of polygenic sex determination in A. burtoni.ResultsUsing mapping in small families in conjunction with restriction-site associated DNA sequencing strategies, we identify associations with sex at loci on linkage group 13 and linkage group 5–14. Inheritance patterns support an XY sex determination system on linkage group 5–14 (a chromosome fusion relative to other cichlids studied), and an XYW system on linkage group 13, and these associations are replicated in multiple families. Additionally, combining our genetic data with comparative genomic analysis identifies another fusion that is unassociated with sex, with linkage group 8–24 and linkage group 16–21 fused in A. burtoni relative to other East African cichlid species.ConclusionsWe identify genetic signals supporting the presence of three previously unidentified sex determination alleles at two loci in the species A. burtoni, strongly supporting the presence of polygenic sex determination system in the species. These results provide a foundation for future mapping of multiple sex determination genes and their interactions. A better understanding of sex determination in A. burtoni provides important context for their use in behavioral studies, as well as studies of the evolution of genetic sex determination and sexual conflicts in East African cichlids.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3177-1) contains supplementary material, which is available to authorized users.

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Section: Resultsmentioning

confidence: 99%

Polygenic sex determination in the cichlid fish Astatotilapia burtoni

et al. 2016

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“…In general, fish are very susceptible to sex reversal triggered by gonadal sex steroid hormones, namely oestrogen or androgens [see Baroiller et al, 2016 in this issue]. Amphibians show a similar plasticity, significantly influenced by both oestrogens and androgens [Nakamura, 2013]. In reptiles, both genotypic and temperature-dependent sex determination have been reported.…”

Section: Discussionmentioning

confidence: 99%

Sex Reversal in Birds

Major

Smith²

2016

Sex Dev

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Sexual differentiation in birds is controlled genetically as in mammals, although the sex chromosomes are different. Males have a ZZ sex chromosome constitution, while females are ZW. Gene(s) on the sex chromosomes must initiate gonadal sex differentiation during embryonic life, inducing paired testes in ZZ individuals and unilateral ovaries in ZW individuals. The traditional view of avian sexual differentiation aligns with that expounded for other vertebrates; upon sexual differentiation, the gonads secrete sex steroid hormones that masculinise or feminise the rest of the body. However, recent studies on naturally occurring or experimentally induced avian sex reversal suggest a significant role for direct genetic factors, in addition to sex hormones, in regulating sexual differentiation of the soma in birds. This review will provide an overview of sex determination in birds and both naturally and experimentally induced sex reversal, with emphasis on the key role of oestrogen. We then consider how recent studies on sex reversal and gynandromorphic birds (half male:half female) are shaping our understanding of sexual differentiation in avians and in vertebrates more broadly. Current evidence shows that sexual differentiation in birds is a mix of direct genetic and hormonal mechanisms. Perturbation of either of these components may lead to sex reversal.

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“…1B). The AR is located on the inverted region of the Y and W chromosomes of Japanese R. rugosa [12], [13]. Expression levels of W - AR are extremely low in R. rugosa embryos compared with Z-AR [16].…”

Section: Discussionmentioning

confidence: 99%

“…In R. rugosa the AR gene is located on the sex (X, Y, Z and W) chromosomes and reportedly on the inverted region of the Y and W chromosomes [12], [13]. Structural rearrangements such as inversions, deletions and translocations are known to induce degradation of native genes by accumulation of deleterious mutations [14].…”

Section: Introductionmentioning

confidence: 99%

Involvement of Androgen Receptor in Sex Determination in an Amphibian Species

et al. 2014

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In mice and humans, the androgen receptor (AR) gene, located on the X chromosome, is not known to be involved in sex determination. In the Japanese frog Rana rugosa the AR is located on the sex chromosomes (X, Y, Z and W). Phylogenetic analysis shows that the AR on the X chromosome (X-AR) of the Korean R. rugosa is basal and segregates into two clusters: one containing W-AR of Japanese R. rugosa, the other containing Y-AR. AR expression is twice as high in ZZ (male) compared to ZW (female) embryos in which the W-AR is barely expressed. Higher AR-expression may be associated with male sex determination in this species. To examine whether the Z-AR is involved in sex determination in R. rugosa, we produced transgenic (Tg) frogs carrying an exogenous Z-AR. Analysis of ZW Tg frogs revealed development of masculinized gonads or ‘ovotestes’. Expression of CYP17 and Dmrt1, genes known to be activated during normal male gonadal development, were up-regulated in the ZW ovotestis. Testosterone, supplied to the rearing water, completed the female-to-male sex-reversal in the AR-Tg ZW frogs. Here we report that Z-AR is involved in male sex-determination in an amphibian species.

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Is a Sex-Determining Gene(s) Necessary for Sex-Determination in Amphibians? Steroid Hormones May Be the Key Factor

Cited by 42 publications

References 117 publications

Polygenic sex determination in the cichlid fish Astatotilapia burtoni

Polygenic sex determination in the cichlid fish Astatotilapia burtoni

Sex Reversal in Birds

Involvement of Androgen Receptor in Sex Determination in an Amphibian Species

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