Cell Cycle Regulation during Spermatogenesis

描述(申请人提供)：这项建议集中在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截然不同(“个体化”)？这个问题将在配子发生和生殖细胞退出减数分裂I的后期前期并进入减数分裂I的中期(G2/MI转变)的减数分裂机制的背景下被解决。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，并确保了染色体的准确分离，从而确定了未来配子的单倍体染色体含量。延伸和突触的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附素的部分凝聚和分解，随后染色体进一步凝聚和个体化。需要检验的中心假设是，G2/MI的转变需要调节的磷酸酶和激活的激酶，随后是凝集素的招募和染色质的重塑，以形成个性化的染色体。在目标1中，将确定对核激酶及其抑制性磷酸酶定位的控制。实验将验证磷酸酶抑制激活极光激酶的假说，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，将确定浓缩的二价染色体的组装要求，以检验这一假设，即在雄性和雌性生殖细胞中的染色体组装都需要粘附素和凝集素的有序组装。在目标3中，将鉴定具有G2/MI停滞表型的独特的小鼠突变体，并将鉴定G2/MI转换所需的先前未知的蛋白质。拟议的研究将阐明与细胞周期相关的机制，即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，因此识别这些调控分子将准确定位配子发生中避孕干预的靶点，以及当它们出错时导致不育或非整倍体的事件。

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.