Cell Cycle Regulation during Spermatogenesis

描述（由申请人提供）：本提案侧重于生殖和染色质生物学中的一个重要问题：中期染色体如何凝聚并在物理上变得不同（“个性化”）？这个问题将在配子体发生和生殖细胞退出减数分裂后期进入减数分裂中期（G2/MI过渡）的减数分裂机制的背景下得到解决。染色质重塑过程对配子至关重要，因为它建立了染色体在纺锤体上的排列，并确保它们的准确分离，以建立未来配子的单倍体染色体含量。延长的和突触的前期染色质重塑为凝聚的二价染色体，包括突触复合体和内聚蛋白的部分凝聚和解体，随后是染色体的进一步凝聚和个体化。要验证的中心假设是G2/MI转变需要调节性磷酸酶和激酶的激活，随后是凝聚蛋白的募集和染色质重塑以形成个体化染色体。在Aim 1中，将确定核激酶及其抑制性磷酸酶的定位控制。实验将验证磷酸酶抑制激活极光激酶的假设，极光激酶构成G2/MI组蛋白H3激酶活性，促进染色体组装和个体化的步骤。在目标2中，将确定凝聚二价染色体组装的要求，以验证在男性和女性生殖细胞中染色体组装都需要凝聚蛋白和凝聚蛋白的有序组装的假设。在Aim 3中，将对具有G2/MI阻滞表型的独特小鼠突变体进行表征，并鉴定G2/MI过渡所需的先前未知蛋白质。这些研究将阐明细胞周期相关的机制，其中染色质被重塑以产生具有分离能力的染色体，这一过程影响体细胞生物学和癌症的起源，非整倍体的病因学和基因组完整性，以及生育和生殖成功的调节。G2/MI“成熟停滞”发生在许多无法解释的人类男性不育和生殖毒性病例中，因此识别这些调节分子将精确定位配子体中避孕干扰和事件的目标，当它们出错时，导致不育或非整倍体。

DESCRIPTION (provided by applicant): This proposal focuses on an important question in reproduction and chromatin biology: How do metaphase chromosomes condense and become physically distinct ("individualized")? This question will be addressed in the context of gametogenesis and the meiotic mechanisms by which germ cells exit late prophase of meiosis I and enter metaphase of the meiosis I division (the G2/MI transition). Chromatin remodeling processes are crucial for gametes because they set up the alignment of chromosomes on the spindle and ensure their accurate segregation to establish the haploid chromosome content of the future gametes. Remodeling of extended and synapsed prophase chromatin into condensed bivalent chromosomes involves partial condensation and disassembly of the synaptonemal complex and cohesin, followed by further condensation and individualization of chromosomes. The central hypothesis to be tested is that the G2/MI transition requires regulatory phosphatases and activation of kinases, followed by recruitment of condensins and chromatin remodeling to form individualized chromosomes. In Aim 1, control of the localization of nuclear kinases and their inhibitory phosphatases will be determined. Experiments will test the hypotheses that phosphatase inhibition activates aurora kinases, which constitute the G2/MI histone H3 kinase activity and promote the steps of chromosome assembly and individualization. In Aim 2, requirements for the assembly of condensed bivalent chromosomes will be determined to test the hypothesis that ordered assembly of both cohesins and condensins is required for chromosome assembly in both male and female germ cells. In Aim 3, unique mouse mutants with G2/MI arrest phenotypes will be characterized and previously unknown proteins required for the G2/MI transition will be identified. The proposed studies will clarify cell cycle-related mechanisms by which chromatin is remodeled to produce segregation-competent chromosomes, a process that impacts on somatic cell biology and origins of cancer, etiology of aneuploidy and genomic integrity, as well as regulation of fertility and reproductive success. G2/MI "maturation arrest" occurs in many unexplained cases of human male infertility and reproductive toxicity, and thus identifying these regulatory molecules will pinpoint targets in gametogenesis for contraceptive interference and events that, when they go awry, lead to infertility or aneuploidy.