Role of Bcl-x in Murine Spermatogenesis

描述（由申请人提供）：细胞凋亡或程序性细胞死亡是由包括受体“引发剂”（例如，TNFR肿瘤坏死因子受体超家族），与肿瘤相关的Bcl-2家族“介质”（例如，Bcl-2、Bax、Bcl-XL）和蛋白酶“执行者”（例如，半胱天冬酶）。这些不育相关基因的过度表达或缺失可阻断精子发生，导致男性不育或不育。例如，转基因小鼠中Bcl-2和Bcl-x的异位表达抑制精原细胞的凋亡并导致不育。此外，Bcl-x在小鼠和人睾丸中的精原细胞和精母细胞中表达。由于与bcl-x无效突变相关的胚胎致死性，尚不可能确定Bcl-x在配子发育中的作用。初步数据支持这一假设，Bcl-x是需要维持小鼠精子发生过程中的精原细胞和精母细胞的存活。 为了解决这一假设，提出了以下具体目标。具体目标1：确定Bcl-x是否维持小鼠睾丸精原细胞群的存活。为此，我们使用Cre-lox系统切除小鼠精母细胞中的bcl-x基因。这种方法将揭示Bcl-x在小鼠睾丸精母细胞存活中的作用。具体目标2：确定Bcl-x和Bax是否是小鼠睾丸精原细胞群体命运决定的拮抗剂。为了做到这一点，我们将产生双小鼠突变体，缺乏来自Cre-lox（bcl-x）和常规（bax）基因敲除策略的bcl-x和bax基因。由此产生的突变体将证明Bcl-x和Bax是否竞争决定小鼠精子发生过程中精母细胞的凋亡命运。

DESCRIPTION (provided by applicant): Apoptosis, or programmed cell death, is a biochemical process that is mediated by a concert of cellular proteins including receptor "initiators" (e.g., TNFR tumor necrosis factor receptor superfamily), the mitochondrial-associating Bcl-2 family "mediators" (e.g., Bcl-2, Bax, Bcl-XL), and the protease "executioners" (e.g., caspases). Spermatogenesis can be blocked by the overexpression or deletion of these apoptosis-related genes, leading to male infertility or sterility. For example, ectopic expression of Bcl-2 and Bcl-x in transgenic mice inhibits apoptosis of spermatogonia and causes infertility. In addition, Bcl-x is expressed in the mouse and human testis within spermatogonia and spermatocytes. Due to the embryonic lethality associated with the bcl-x null mutation, it has not been possible to ascertain the role of Bcl-x in gamete development. Preliminary data support the hypothesis that Bcl-x is required to maintain the survival of spermatogonia and spermatocytes during murine spermatogenesis. To address this hypothesis the following specific aims are proposed. Specific Aim 1: Determine whether Bcl-x maintains the survival of spermatogonial cell populations in the mouse testes. To do this, we ablate the bcl-x gene in murine spermatocytes using the Cre-lox system. This approach will reveal the role of Bcl-x in spermatocyte survival in the mouse testis. Specific Aim 2: Determine whether Bcl-x and Bax are antagonists in the fate determination of the spermatogonial cell populations in the mouse testes. To do this, we will generate double mouse mutants that lack both the bcl-x and bax genes derived from Cre-lox (bcl-x) and conventional (bax) gene knockout strategies. Resultant mutants will demonstrate whether Bcl-x and Bax compete in determining the apoptotic fate of spermatocytes during murine spermatogenesis.