Cell Cycle Regulation during Spermatogenesis

描述（由申请人提供）：本提案关注生殖和染色质生物学中的一个重要问题：中期染色体如何浓缩并在物理上变得不同（“个体化”）？这个问题将在配子发生和减数分裂机制的背景下，生殖细胞退出后期前期的减数分裂I和进入中期的减数分裂I分裂（G2/MI过渡）。染色质重塑过程对配子至关重要，因为它们建立了纺锤体上染色体的排列，并确保其准确分离，以建立未来配子的单倍体染色体内容。延长和联会前期染色质重塑为浓缩的二价染色体涉及联会复合体和粘着蛋白的部分浓缩和解体，随后是染色体的进一步浓缩和个体化。要测试的中心假设是，G2/MI转换需要调节磷酸酶和激酶的激活，然后通过凝聚素的募集和染色质重塑形成个性化的染色体。在目标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，并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，以检验以下假设：在雄性和雌性生殖细胞中染色体组装都需要凝聚素和凝聚素的有序组装。在目标3中，将表征具有G2/MI停滞表型的独特小鼠突变体，并将鉴定G2/MI转换所需的先前未知的蛋白质。拟议的研究将阐明细胞周期相关的机制，通过该机制，染色质被重塑以产生分离能力染色体，这一过程影响体细胞生物学和癌症起源，非整倍性和基因组完整性的病因学，以及生育力和生殖成功的调节。G2/MI“成熟停滞”发生在许多原因不明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查明配子发生中避孕干扰的目标以及当它们出错时导致不育或非整倍性的事件。

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.