| Budget Amount *help |
¥16,770,000 (Direct Cost: ¥12,900,000、Indirect Cost: ¥3,870,000)
Fiscal Year 2010: ¥5,590,000 (Direct Cost: ¥4,300,000、Indirect Cost: ¥1,290,000)
Fiscal Year 2009: ¥5,330,000 (Direct Cost: ¥4,100,000、Indirect Cost: ¥1,230,000)
Fiscal Year 2008: ¥5,850,000 (Direct Cost: ¥4,500,000、Indirect Cost: ¥1,350,000)
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| Research Abstract |
In most vertebrate, sex is determined genetically. Mammals and birds with cytogenetically well-differentiated sex chromosome have common sex determination system in each class, while various sex-determination mechanisms have evolved independently in fishes, and most species with genetic sex determination have undifferentiated sex chromosomes. The sex-determining gene Dmy has only been found in medaka fish (Oryzias latipes) and one of its closest relatives O. curvinotus. Molecular phylogenetic analysis of these species suggested that Dmy evolved in the common ancestor of O. latipes, O. curvinotus and O. luzonensis and then disappeared in O. luzonensis.
Here we demonstrated that Y-linked allele of a TGF-β superfamily gene, Gsdf (gonadal soma derived growth factor) functions as the sex-determining gene in O. luzonensis. Although Gsdf exists on both of the sex chromosomes (GsdfY and GsdfX), only GsdfY shows male specific high expression during sex determination period. Gsdf is a downstream gene of Dmy in the sex determination cascade of medaka fish, suggesting that emergence of new allele of Gsdf independent of Dmy signal has lead to appearance of a novel sex determining gene in O. luzonensis.
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