性别决定的遗传学因分类单元而异,有时甚至在一个物种内。斑马鱼的主要驯化品系(Daniorerio),包括AB和TU,缺乏强烈的遗传性别决定位点,但是菌株最近来自自然,像纳迪亚(NA),拥有ZZ男性/ZW女性染色体性别决定系统。AB鱼通过幼年卵巢阶段,形成卵母细胞,这些卵母细胞在变成雌性的鱼中存活,但在变成雄性的鱼中死亡。为了了解NA斑马鱼的性腺发育机制,我们研究了正在发育的ZZ和ZW鱼的组织学和单细胞转录组学。ZW鱼在受精后22天(dpf)发育卵母细胞,但ZZ鱼直接形成睾丸,避免幼年卵巢期。一些ZW和WW鱼的性腺,然而,发育的卵母细胞随着性腺变成睾丸而死亡,模仿AB鱼,表明雌激素来源的AB菌株是染色体WW。19dpf性腺的单细胞RNA-seq在ZZ和ZW鱼中显示出相似的细胞类型,包括生殖细胞,性腺支持细胞的前体,类固醇细胞,间质/基质细胞,和免疫细胞,与双潜能幼年性腺一致。相比之下,30dpf性腺的scRNA-seq显示ZZ性腺中的细胞具有睾丸支持的转录组特征,莱迪格,和生殖细胞,而ZW性腺有颗粒细胞,卵泡膜细胞,和正在发育的卵母细胞。两种性别基因型的造血和血管细胞相似。这些结果表明,幼年的NA斑马鱼最初发育双势性腺;NAW染色体上的一个因子,或者少于两条Z染色体,对启动卵母细胞发育至关重要;没有W因子,或者两个Z剂量,NA性腺直接发育成睾丸,而不经过幼年卵巢阶段。AB和TU菌株的性别决定模拟NAZW和WW斑马鱼,提示驯化过程中Z染色体丢失。NA菌株的遗传分析将有助于我们了解性别决定机制的演变。
The genetics of sex determination varies across taxa, sometimes even within a species. Major domesticated strains of zebrafish (Danio rerio), including AB and TU, lack a strong genetic sex determining locus, but strains more recently derived from nature, like Nadia (NA), possess a ZZ male/ZW female chromosomal sex-determination system. AB fish pass through a juvenile ovary stage, forming oocytes that survive in fish that become females but die in fish that become males. To understand mechanisms of gonad development in NA zebrafish, we studied histology and single cell transcriptomics in developing ZZ and ZW fish. ZW fish developed oocytes by 22 days post-fertilization (dpf) but ZZ fish directly formed testes, avoiding a juvenile ovary phase. Gonads of some ZW and WW fish, however, developed oocytes that died as the gonad became a testis, mimicking AB fish, suggesting that the gynogenetically derived AB strain is chromosomally WW. Single-cell RNA-seq of 19dpf gonads showed similar cell types in ZZ and ZW fish, including germ cells, precursors of gonadal support cells, steroidogenic cells, interstitial/stromal cells, and immune cells, consistent with a bipotential juvenile gonad. In contrast, scRNA-seq of 30dpf gonads revealed that cells in ZZ gonads had transcriptomes characteristic of testicular Sertoli, Leydig, and germ cells while ZW gonads had granulosa cells, theca cells, and developing oocytes. Hematopoietic and vascular cells were similar in both sex genotypes. These results show that juvenile NA zebrafish initially develop a bipotential gonad; that a factor on the NA W chromosome, or fewer than two Z chromosomes, is essential to initiate oocyte development; and without the W factor, or with two Z doses, NA gonads develop directly into testes without passing through the juvenile ovary stage. Sex determination in AB and TU strains mimics NA ZW and WW zebrafish, suggesting loss of the Z chromosome during domestication. Genetic analysis of the NA strain will facilitate our understanding of the evolution of sex determination mechanisms.