A duplicated, y-linked copy of the anti-mullerian gene determines testicular formation in patogonian pejerrey Odontesthes hatcheri.

RICARDO S. HATTORI; YU MURAI; MIHO OURA; SHUJI MASUDA; SULLIP MAJHI; TAKASHI SAKAMOTO; JUAN I. FERNANDINO; GUSTAVO M. SOMOZA; MASASHI YOKOTA; CARLOS A. STRÜSSMANN

Cochin

Congreso; 9th International Symposium on Reproductive Physiology of Fish; 2011

Introduction: In many vertebrates, gonadal sex determination follows a sequence ofgenetically programmed events. However, only a handful of genes have been described asthe ultimate triggers of differentiation and the mechanism of genotypic sex determinationstill remains elusive for most vertebrates. In order to clarify the process of genotypic sexdetermination in the Atherinopsid fish Patagonian pejerrey (Odontesthes hatcheri), aspecies with the XX-XY sex determining system, we have conducted transcriptomicanalyses of several sex-related genes during early sex differentiation. Those studies lead tothe identification of a duplicated copy of the anti-Müllerian hormone (amh) gene whichplays a critical role in sex determination of this species.Methods: The complete cDNA sequences of the two forms of amh were obtained bydegenerated RT-PCR and RACE PCR using larvae and adult samples. The non-transcribedsequence of the male-specific locus was obtained by PCR of genomic DNA from an XYindividual. Fluorescence in situ hybridization (FISH) was performed for chromosomemapping. mRNA expression was analyzed by RT-PCR and in situ hybridization duringgonadal sex differentiation. Functional analysis was conducted by microinjection ofantisense morpholinos.Results and Discussion: The male-specific amh (termed amhy) gene showed 92.2% ofamino acid identity in relation to the autosomal one (termed amha). Physical mapping ofamhy allowed the identification of the Y chromosome in this species and its transcriptswere detected from 6 days after fertilization in presumptive Sertoli cells. Amhy knockdownin XY embryos resulted in the development of ovaries.Conclusion: These results establish amhy as a candidate for the master sex-determininggene in O. hatcheri and for the first time associate a hormone-related gene, a member ofthe TGF-β superfamily, with such a role.