Retinoic acid metabolic genes, meiosis, and gonadal sex differentiation in zebrafish.
Retinoic acid metabolic genes, meiosis, and gonadal sex differentiation in zebrafish.
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DOI：
10.1371/journal.pone.0073951
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Postlethwait JH
中科院分区：
文献类型：
--
作者：
Rodríguez-Marí A;Cañestro C;BreMiller RA;Catchen JM;Yan YL;Postlethwait JH
为了帮助理解斑马鱼性别决定的难以捉摸的机制，我们研究了在促性腺激素减数分裂开始时调节维甲酸（RA）产生和分解的遗传机制。结果揭示了斑马鱼和哺乳动物之间意想不到的机制差异。保守的同源性和表达分析表明，斑马鱼中的cyp26a1及其在四足动物中的类似Cyp26b1分别成为可用于性腺ra降解酶的主要基因，显示出脊椎动物基因组重复（VGD）类似物的谱系特异性亚功能化。实验表明，斑马鱼在性腺中表达编码ra合成酶的aldh1a2，而不是在小鼠的中肾中表达。所有斑马鱼双电位性腺的生殖细胞都被早期减数分裂标记sycp3标记，这表明斑马鱼减数分裂的开始不像小鼠那样是两性二态的，并且独立于小鼠所需的Stra8，而在硬骨鱼中则缺失。对丧失生殖细胞的死端敲除斑马鱼的分析揭示了性腺aldh1a2和cyp26a1表达的不依赖生殖细胞的开始和维持。在减数分裂开始后，cyp26a1的体细胞表达成为两性二态：在睾丸中上调，而在卵巢中没有上调。表达突触复合体基因sycp3的减数分裂生殖细胞占据了缺乏cyp26a1表达的体细胞岛，正如cyp26a1作为减数分裂抑制因子的假设所预测的那样。与这一假设相一致的是，雌性进入前体减数分裂停滞期的卵母细胞中cyp26a1表达上调，而恢复减数分裂的卵母细胞中cyp26a1表达下调。在减数分裂阻滞的卵母细胞中，cyp26a1和多能生殖细胞干细胞标记物pou5f1（oct4）的共表达与小鼠实验中促进生殖细胞存活和防止细胞凋亡的作用一致，这些机制是斑马鱼性腺向雌性途径转移的核心机制。
To help understand the elusive mechanisms of zebrafish sex determination, we studied the genetic machinery regulating production and breakdown of retinoic acid (RA) during the onset of meiosis in gonadogenesis. Results uncovered unexpected mechanistic differences between zebrafish and mammals. Conserved synteny and expression analyses revealed that cyp26a1 in zebrafish and its paralog Cyp26b1 in tetrapods independently became the primary genes encoding enzymes available for gonadal RA-degradation, showing lineage-specific subfunctionalization of vertebrate genome duplication (VGD) paralogs. Experiments showed that zebrafish express aldh1a2, which encodes an RA-synthesizing enzyme, in the gonad rather than in the mesonephros as in mouse. Germ cells in bipotential gonads of all zebrafish analyzed were labeled by the early meiotic marker sycp3, suggesting that in zebrafish, the onset of meiosis is not sexually dimorphic as it is in mouse and is independent of Stra8, which is required in mouse but was lost in teleosts. Analysis of dead-end knockdown zebrafish depleted of germ cells revealed the germ cell-independent onset and maintenance of gonadal aldh1a2 and cyp26a1 expression. After meiosis initiated, somatic cell expression of cyp26a1 became sexually dimorphic: up-regulated in testes but not ovaries. Meiotic germ cells expressing the synaptonemal complex gene sycp3 occupied islands of somatic cells that lacked cyp26a1 expression, as predicted by the hypothesis that Cyp26a1 acts as a meiosis-inhibiting factor. Consistent with this hypothesis, females up-regulated cyp26a1 in oocytes that entered prophase-I meiotic arrest, and down-regulated cyp26a1 in oocytes resuming meiosis. Co-expression of cyp26a1 and the pluripotent germ cell stem cell marker pou5f1(oct4) in meiotically arrested oocytes was consistent with roles in mouse to promote germ cell survival and to prevent apoptosis, mechanisms that are central for tipping the sexual fate of gonads towards the female pathway in zebrafish.