DNA Damage Response Pathways in Meiotic Sex Chromosome Inactivation

摘要 本项目的目的是阐明该基因的调控机制和生物学意义。 男性生殖细胞中性染色体的表观遗传程序。在雄性减数分裂期间， 染色体在称为减数分裂性染色体失活（MSCI）的过程中表观遗传学沉默， 这是精子发生所必需的。在上一次拨款期间，我们阐明了基本的 的机制，并证明了DNA损伤反应（DDR）因子的作用是必不可少的 监管部门MSCI的建立需要组蛋白变体H2 AX（γ H2 AX）的磷酸化以扩散 从轴到性染色体的染色体范围。此过程由MDC 1指导， 在粗线期开始时，γ H2 AX的结合伴侣。在MDC 1的下游，SCML 2，一个生殖系- 特异性Polycomb蛋白，被募集到含有γ H2 AX的核小体中，并为表观遗传学所需。 编程.在上一个项目期间，我们意外地发现，MSCI的启动与 活性DNA去甲基化最初，DNA去甲基化是由MDC 1指导的，并且先于DNA去甲基化。 沉默组蛋白修饰的建立。在这个更新应用程序中，我们将测试中心假设， DDR途径调节活跃的DNA去甲基化，使性别的表观遗传编程成为可能 男性生殖所必需的染色体。虽然DNA甲基化通常与基因 沉默，我们提出DNA去甲基化与MSCI中的基因沉默有关。我们的数据表明 MSCI中的去甲基化涉及两个主要阶段：初始阶段由DDR途径介导， 粗线期早期（Aim 1）和后期由DDR下游的SCML 2介导， 粗线期（Aim 2）。这项研究将建立DDR信号和活性DNA之间的新联系 去甲基化，并将进一步阐明性别的表观遗传编程的生物学意义 染色体，这对男性生殖至关重要。

ABSTRACT The objective of this project is to elucidate the regulatory mechanisms and biological significance of the epigenetic programming of the sex chromosomes in the male germline. During male meiosis, unsynapsed sex chromosomes are epigenetically silenced in a process called meiotic sex chromosome inactivation (MSCI), which is necessary for spermatogenesis. During the term of the previous grant, we elucidated the underlying mechanisms of MSCI and demonstrated the role of DNA damage response (DDR) factors as essential regulators. Establishment of MSCI requires phosphorylation of the histone variant H2AX (γH2AX) to spread from the axes to the chromosome-wide domain of the sex chromosomes. This process is directed by MDC1, a binding partner of γH2AX, at the onset of the pachytene stage. Downstream of MDC1, SCML2, a germline- specific Polycomb protein, is recruited to γH2AX-containing nucleosomes and required for epigenetic programming. During the last project period, we unexpectedly found that initiation of MSCI is tightly coupled to active DNA demethylation. Initially the DNA demethylation is directed by MDC1 and precedes the establishment of silent histone modifications. In this renewal application, we will test the central hypothesis that the DDR pathway regulates active DNA demethylation, enabling the epigenetic programming of sex chromosomes necessary for male reproduction. While DNA methylation is generally associated with gene silencing, we propose that DNA demethylation is linked to gene silencing in MSCI. Our data suggest that demethylation in MSCI involves two major phases: the initial phase is mediated by the DDR pathway at the early pachytene stage (Aim 1) and the later phase is mediated by SCML2 downstream of the DDR at the mid- pachytene stage (Aim 2). This study will establish a novel link between DDR signaling and active DNA demethylation, and will further elucidate the biological significance of the epigenetic programming of the sex chromosomes, which is essential for male reproduction.