Sexual identity and germ cell differentiation in the Drosophila ovary

描述(申请人提供)：在成人中，组织的维持和修复依赖于能够产生自我更新和分化的子代细胞的稳定的干细胞群体。了解这一过程是如何调控的至关重要，因为过度分化会导致干细胞枯竭和组织衰老，而未能进入分化途径可能会导致增殖细胞积累和肿瘤形成。通过比较雄性和雌性生殖系干细胞(GSC)在果蝇卵巢和睾丸中的行为，揭示了调控自我更新/分化决策的调节机制的性别二型性适应。然而，很少有人注意到这些差异是如何实现的。Salz实验室的数据支持一种新的模型，在该模型中，女性特有的RNA结合蛋白SXL共同控制生殖系中的性别认同和自我更新/分化决定。没有SXL蛋白的GSC不能成功地执行自我更新以分化细胞命运的切换。分化失败伴随着一组男性特异性标志物的不适当表达，继续增殖和形成肿瘤。SXL编码一种普遍表达的女性特异性RNA结合蛋白。在体细胞中，它全局地调节雌性特有的所有方面 发展和行为。然而，它在生殖系中的作用模式仍然知之甚少。这项新提案中的研究使用了一种综合的实验方法来解决这个问题，该方法将经典遗传学和分子遗传学与RNA/蛋白质生物化学相结合。在目标1中，我们专注于SXL如何控制生殖细胞分化，首先我们的研究表明，SXL通过抑制保守的干细胞因子Nanos的翻译而促使退出干细胞的命运。在目标2中，我们关注SXL如何维持性别认同，从初步研究开始，SXL通过JAK/STAT信号通路发挥作用，抑制男性特有的生殖细胞行为。这项提案中的研究所产生的知识将阐明将性别认同和 自我更新/分化决定，并将提供信息，为什么这一途径的中断导致生殖细胞肿瘤。来自果蝇种系等模型系统的信息将为干细胞如何在其他实验上不太容易处理的系统中控制自我更新/分化决策提供关键见解。更广泛地说，从我们的动物模型研究中获得的信息将阐明RNA调节器在时间和空间上差异调控基因表达所使用的策略。

DESCRIPTION (provided by applicant): In adults, tissue maintenance and repair depends on a stable population of stem cells that can give rise to both self-renewing and differentiating daughter cells. An understanding of how this process is regulated is of fundamental importance because an excess of differentiation can lead to stem cell depletion and tissue senescence, while a failure to enter the differentiation pathway can lead to an accumulation of proliferating cells and tumor formation. A comparison of male and female germline stem cell (GSC) behavior in Drosophila ovaries and testis, two of the premier model systems for the study of stem cells in their natural environment, reveals sexually dimorphic adaptations of the regulatory mechanisms governing the self- renewal/differentiation decision. Little attention, however, has been paid to how these differences are achieved. Data emerging from the Salz lab supports a novel model in which the female specific RNA binding protein Sex-lethal (Sxl) jointly controls sexual identity and the self-renewal/differentiation decision in the germline. GSCs without Sxl protein fail to successfully execute the self-renewal to differentiation cell fate switch. The failure to differentiate is accompanied by the inappropriate expression of a set of male specific markers, continued proliferation and formation of a tumor. Sxl encodes a ubiquitously expressed female- specific RNA binding protein. In somatic cells it globally regulates all aspects of female-specific development and behavior. Its mode of action in the germline, however, remains poorly understood. The studies in this new proposal address this issue using an integrated experimental approach that combines classical and molecular genetics with RNA/protein biochemistry. In Aim 1 we focus on how Sxl controls germ cell differentiation, beginning with our studies showing that Sxl prompts the exit from the stem cell fate by repressing translation of the conserved stem cell factor nanos. In Aim 2 we focus on how Sxl maintains sexual identity, beginning with preliminary studies showing that Sxl acts through the Jak/Stat signaling pathway to repress male-specific germ cell behavior. The knowledge generated by the studies in this proposal will illuminate the intrinsic regulatory mechanisms that integrate sexual identity and the self- renewal/differentiation decision, and will provide information about why disruptions in this pathway lead to germ cell tumors. Information from model systems such as the Drosophila germline will provide key insights into how stem cells control the self-renewal/differentiation decision in other, less experimentally tractable systems. More generally, the information gained from our animal model studies will illuminate strategies used by RNA regulators to differentially regulate gene expression in time and space.