Gene Dosage in Mammalian Sexual Development

描述（由申请人提供）：在哺乳动物中，性别决定是决定双势性腺进入睾丸或卵巢的发育命运的胚胎过程。它是由Sry基因（一种编码转录因子的y连锁基因）在男性体内的存在或在女性体内的缺失引发的。人类性别决定障碍会导致性腺功能缺陷，并可能导致内外生殖器的一系列异常，从轻微的性别模糊到完全的性别逆转。尽管在人类和小鼠模型中发现了几个性别决定基因，但绝大多数患有性别决定障碍的XY患者无法从遗传学上解释，这表明存在其他遗传因素参与了这一过程。此外，已知的性别决定基因的分子机制尚不清楚。我们的首要目标是破译胚胎性腺分化的分子事件，因此性别决定的过程。为了实现这一目标，我们将研究一种性发育障碍的小鼠模型。我们将在C57BL/6J-YPOS小鼠模型中发现新的遗传因素，在该模型中，源自家养菌株（YPOS）的Y染色体与C57BL/6J背景的组合导致睾丸发育中断。由于我们的初步结果表明，小鼠11号染色体上的一个基因区在C57BL/6J- ypos模型中可以防止性别逆转，我们将验证这个基因区携带一个或几个基因，这些基因在C57BL/6J和供体congenic片段之间存在差异，并且这种差异负责保护。我们将通过创建亚同源区和识别与保护表型相关的最小同源片段来缩小同源区（目的1）。我们还将筛选和选择候选基因，研究它们的表达谱及其与已知性别决定基因的功能关系，并测试它们的表达改变是否会导致胚胎性腺发育的改变（目的2）。最后，我们将在C57BL/6J-YPOS模型中研究XY性别逆转的分子机制，并分析基因区对性腺发育的保护作用的分子和细胞性质（Aim 3）。解剖哺乳动物性别决定的分子途径对于理解性腺发育的基本性别差异和人类性发育障碍的病理生理学至关重要。公共卫生相关性：我们生命中最具决定性的时刻之一是在子宫里，我们开始走向男性或女性的道路，而触发这一时刻的是Sry基因在男性中开启或在女性中关闭；然而，在Sry作用后发生的许多分子事件仍然知之甚少，在人类中，性发育中断的发生率为0.5%至1%。由于只有25%的人类性别决定的病理是遗传解释的，我们建议通过使用异常性发育的小鼠模型来识别参与这一过程的新基因。这一建议将阐明关于男性和女性如何变得不同的基本问题，并将改进先天性性发育障碍患者的遗传分类和诊断方法。

DESCRIPTION (provided by applicant): In mammals, sex determination is the embryonic process that determines the developmental fate of the bipotential gonad into either testis or ovary. It is triggered by the presence, in males, or the absence in females, of Sry, a Y-linked gene encoding a transcription factor. Disorders of human sex determination cause defects in gonadal function and can result in a spectrum of abnormalities in the internal and external genitalia, ranging from mild sexual ambiguities to complete sex reversal. Although several sex-determining genes have been identified in humans and mouse models, the vast majority of XY patients with disorders of sex determination are not explained genetically, suggesting the existence of other genetic factors involved in this process. In addition, the molecular mechanisms of known sex-determining genes are poorly understood. Our overarching goal is to decipher the molecular events underlying the differentiation of the embryonic gonad, and therefore the process of sex determination. To achieve this objective, we will investigate a mouse model of disorders of sex development. We will identify novel genetic factors protecting against XY sex reversal in the C57BL/6J-YPOS mouse model in which the combination of a Y chromosome originating from a domesticus strain (YPOS) and a C57BL/6J background results in disrupted testicular development. Since our preliminary results show that a congenic region from mouse chromosome 11 protects against sex reversal in the C57BL/6J-YPOS model, we will test the hypothesis that this congenic region carries one or several genes that differ between C57BL/6J and the donor, congenic, fragment and that the difference is responsible for the protection. We will narrow down the congenic region by creating sub-congenic areas and identifying a minimal congenic fragment associated with the protection phenotype (Aim 1). We will also screen for and select candidate genes, investigate their expression profile and their functional relationship with known sex-determining genes and test if the alteration of their expression causes modifications in embryonic gonadal development (Aim 2). Finally, we will investigate the molecular mechanisms of XY sex reversal in the C57BL/6J-YPOS model and analyze the molecular and cellular nature of protective effect from the congenic region on gonadal development (Aim 3). Dissecting the molecular pathway of mammalian sex determination will be crucial in understanding the basic sex differences in gonadal development and the pathophysiology of human disorders of sex development. PUBLIC HEALTH RELEVANCE: One of the most defining moment of our lives is when, in the womb, we embark on a male or female path, and what triggers this moment is when the gene Sry is turned on in males, or stays off in females; yet, many molecular events that happen after Sry action remain poorly understood, and in humans, disruption of sexual development occurs at a frequency of 0.5% to 1%. As only 25% of human pathologies of sex determination are explained genetically, we propose to identify new genes involved in this process by using a mouse model of abnormal sex development. This proposal will elucidate basic questions about how males and females become different, and will improve genetic classification and diagnostic methods of patients born with disorders of sex development.