Data from: Dmrt1 polymorphism covaries with sex-determination patterns in Rana temporaria

Patterns of sex-chromosome differentiation and gonadal development have been shown to vary among populations of Rana temporaria along a latitudinal transect in Sweden. Frogs from the northern-boreal population of Ammarnäs displayed well-differentiated X and Y haplotypes, early gonadal differentiation, and a perfect match between phenotypic and genotypic sex. In contrast, no differentiated Y haplotypes could be detected in the southern population of Tvedöra, where juveniles furthermore showed delayed gonadal differentiation. Here, we show that Dmrt1, a gene that plays a key role in sex determination and sexual development across all metazoans, displays significant sex differentiation in Tvedöra, with a Y-specific haplotype distinct from Ammarnäs. The differential segment is not only much shorter in Tvedöra than in Ammarnäs, it is also less differentiated and associates with both delayed gonadal differentiation and imperfect match between phenotypic and genotypic sex. Whereas Tvedöra juveniles with a local Y haplotype tend to ultimately develop as males, those without it may nevertheless become functional XX males, but with strongly female-biased progeny. Our findings suggest that the variance in patterns of sex determination documented in common frogs might result from a genetic polymorphism within a small genomic region that contains Dmrt1. They also substantiate the view that recurrent convergences of sex determination toward a limited set of chromosome pairs may result from the co-option of small genomic regions that harbor key genes from the sex-determination pathway.

已有研究表明，瑞典境内沿纬度样带分布的普通林蛙（Rana temporaria）不同种群间，其性染色体分化与性腺发育模式存在显著差异。来自阿马纳斯（Ammarnäs）北方寒带种群的个体，其X与Y单倍型分化明显，性腺分化启动更早，且表型性别与基因型性别完全匹配。与之相反，南部种群特韦德拉（Tvedöra）中未检测到分化的Y单倍型，该种群的幼蛙还存在性腺分化延迟的现象。
本研究发现，在所有后生动物中均参与性别决定与性腺发育关键调控的Dmrt1基因（Dmrt1），在特韦德拉种群中呈现出显著的性别分化特征，其Y染色体特异性单倍型与阿马纳斯种群存在明显差异。与阿马纳斯种群相比，特韦德拉种群的性染色体差异区段不仅长度更短，分化程度也更低，且该区段与性腺发育延迟、表型性别与基因型性别不匹配均存在关联。
携带本地Y单倍型的特韦德拉幼蛙最终大多发育为雄性，而不携带该单倍型的个体虽可发育为具有功能的XX雄蛙，但其后代会呈现强烈的雌性偏倚比例。本研究结果表明，普通林蛙中记录到的性别决定模式变异，可能源于包含Dmrt1基因的小型基因组区域内的遗传多态性。同时，该结果也支持了以下观点：性别决定反复趋同演化至有限的几对染色体，可能是由于招募了携带性别决定通路关键基因的小型基因组区域所致。