Gene Dosage in Mammalian Sexual Development

描述（由申请人提供）：在哺乳动物中，当未分化的双潜能胚胎性腺（也称为生殖嵴）变成睾丸或卵巢时，性别就确定了。哺乳动物性别决定的分子机制尚不清楚，因为已知的遗传缺陷仅在少数性别逆转患者（XX名男性，XY名女性，XX名真正的雌雄同体）中被发现。直到最近，只有SRY、SOX9、DAX1、WT1和SF1等转录因子参与了这一过程。我们和其他人发现WNT-4是一种新的性别决定信号分子，当缺失时，它负责XX小鼠幼崽的雄性化，当在人类中复制和过表达时，它负责XY性别逆转。我们的目标是利用转基因动物模型评估Wnt-4剂量对哺乳动物性发育的影响（Specific Aim 1），并利用Sertoli细胞系系统表征Wnt-4在性别决定途径中的作用的分子机制（Specific Aim 2）。我们将通过评估不同剂量的WNT- 4对转基因小鼠性发育的影响来验证哺乳动物性别决定对基因剂量敏感的假设。我们还将通过确定Wnt-4的生理靶点和表征Wnt-4表达和信号传导的控制机制来测试所提出的性别决定模型的有效性。最后，我们已经证明WNT-4破坏XY性腺的血管发育。由于XX和XY性腺之间存在不同的血管生成机制，在发育中的睾丸和卵巢中建立了不同的动脉系统，我们将测试WNT-4如何影响性腺的性别特异性血管形成（Specific Aim 3）。解剖哺乳动物性别决定的分子途径对于理解性腺的发育和人类性发育障碍的病理生理学至关重要。

DESCRIPTION (provided by applicant): In mammals, sex is determined when the undifferentiated and bipotential embryonic gonad, otherwise known as the genital ridge, becomes either a testis or an ovary. The molecular mechanisms of mammalian sex determination are poorly understood as known genetic defects have been identified in only a minority of sex-reversed patients (XX males, XY females, XX true hermaphrodites). Until recently, only transcription factors such as SRY, SOX9, DAX1, WT1 and SF1 were known to be involved in this process. We and others showed that WNT-4 is a new sex-determining signaling molecule responsible for masculinization of XX mouse pups when deleted, and for XY sex reversal when duplicated and overexpressed in humans. Our goal is to assess the influence of Wnt-4 dosage on mammalian sexual development using a transgenic animal model (Specific Aim 1), and to characterize the molecular mechanisms of Wnt-4 action in the sex determination pathway using a Sertoli cell line system (Specific Aim 2). We will test the hypothesis that mammalian sex determination is sensitive to gene dosage by assessing the effect of various doses of WNT- 4 on sexual development of transgenic mice. We will also test the validity of a proposed model for sex determination by identifying the physiological target of Wnt-4 and by characterizing the mechanisms of control of Wnt-4 expression and signaling. Finally, we have shown that WNT-4 disrupts the vascular development of XY gonads. Since there are divergent angiogenic mechanisms between XX and XY gonads that establish the distinct arterial systems in developing testes and ovaries, we will test how WNT-4 influences the sex-specific vascularization of the gonads (Specific Aim 3). Dissecting the molecular pathway of mammalian sex determination will be crucial in understanding the development of the gonads, and the pathophysiology of human disorders of sexual development.