Functional Analysis on the sex-related genes using the inter-specific hybrids among Oryzias fishes.

medaka Hd-rR株系雌性与雄性进行种间杂交，XY型鱼均发育为雌性，但用medaka HO4C株系雌性进行杂交时，未出现性别逆转现象。利用HdrR和HO4C之间的多态性，我们进行了连锁分析，发现了连锁组17上负责性别逆转的位点（hml）。对杂种Dmy的表达分析表明，性别反转是由于在性别决定阶段Dmy的表达减少，表明hml与Dmy的表达调控有关。hml的精细定位将17号染色体上的位点区域缩小到624 KB。我们正在继续对hml的鉴定进行研究。

Inter-specific hybrids between female of Hd-rR strain of medaka and male Oryzias curvinotus, all XY fish developed into females, but when we used females of HO4C strain of medaka for hybridization, no sex-reversals appeared. Utilizing the polymorphism between HdrR and HO4C, we conducted a linkage analysis to uncover a locus(hml) on the linkage group 17 responsible for the sex reversal. The analysis of the expression of Dmy in the hybrid revealed that the sex-reversal resulted from the decrease of the expression of Dmy during the sex-determining stage, indicating that hml is related to the regulation of Dmy expression. Fine mapping for hml narrowed the region of the locus on the chromosome 17 to 624 KB. We are continuing the study for the identification of hml.