PRDM9 and Control of Meiotic Progression

项目总结项目D PRDM9是重组和转录的重要调控因子；它在减数分裂过程中唯一表达；它的缺失阻碍了减数分裂进程和配子发生。因此，Prdm9在功能上进化为满足特定的减数分裂和配子发生需求；然而，这些需求的全部范围和性质尚不清楚。特别是PRDMS在减数分裂过程中的作用，其表达模式，它与减数分裂相关核结构和结构域的关系，以及PRDMS的结构如何介导其不同的酶效应，都是未知的。该项目广泛的长期目标是通过使用细胞和遗传策略来确定PRDMS何时(目标1)、在哪里(目标2)以及如何(目标3)促进重组位点激活以及成功的减数分裂和精子发生的机制来解决这些问题。目标1的结果将确定减数分裂的哪些步骤受到PRDMS的控制，以及PRDMS的功能是持续的还是仅在特定的减数分裂或生精亚阶段需要。由于初步证据表明PRDMS在细胞核中的占位可能是暂时的，这对于确定何时设置染色质标记、何时发生重组位点选择以及何时可能进行转录控制是重要的。AIM 2的结果将确定PRDMS蛋白的定位，并使用PrdmQ突变体和成熟的小鼠减数分裂突变模型来确定PRDMS功能对减数分裂至关重要的蛋白质的要求或依赖程度，包括那些介导染色体突触和重组的蛋白质。目标3的结果将确定PRDMS在减数分裂和配子发生中的哪些功能需要其组蛋白甲基转移酶活性或其转录调节KRAB结构域。最近的研究结果表明，非编码RNA是PRDMS的转录靶标之一。与项目B和C的目标合作，这一目标将定义PRDMS特有的基因组序列靶标和功能序列簇，这些序列由特定的PRDMS结构域进行表观标记和/或转录，以及它们与依赖PRDMS的重组热点的关系。总之，该项目的结果将补充其他项目，将PRDMS的功能设置为明确的减数分裂染色体事件序列，更具体地说，解决其多重作用的分子基础，并有助于理解PRDMS如何适应控制减数分裂和配子发生的更大蛋白质网络。该项目涉及的PRDMS生物学的一个重要方面是，PRDMS是生育力的主要决定因素；在没有PRDMS的情况下发生的异常重组和减数分裂失败可能导致人类不育或出生缺陷。

PROJECT SUMMARY PROJECT D PRDM9 is an important regulator of recombination and transcription; it is uniquely expressed during meiosis; and its absence arrests meiotic progress and gametogenesis. Thus Prdm9 has evolved functionally to serve specific meiotic and gametogenic requirements; however, the full range and nature of these requirements is not known. In particular, the roles of PRDMS in the sequence of meiotic events, its pattern of expression, its relationship to meiotically relevant nuclear structures and domains, and how the structure of PRDMS mediates its varied enzymatic effects are all unknown. The broad, long-term goals of this project are to resolve these issues by using both cellular and genetic strategies to identify mechanisms of when (Aim 1), where (Aim 2) and how (Aim 3) PRDMS promotes recombination site activation, and successful meiosis and spermatogenesis. The results of Aim 1 will establish which steps in meiosis are subject to PRDMS control and whether PRDMS function is required continuously or only at specific meiotic or spermatogenic substages. Because preliminary evidence suggests that PRDMS occupancy in nuclei may be transient, this is important for determining when chromatin marks are set, when recombination site selection occurs, and when transcriptional control is possible. The results of Aim 2 will determine localization of the PRDMS protein and use both PrdmQ mutants and well established mouse meiosis mutant models to determine the extent to which PRDMS function is required for or dependent on proteins crucial for meiosis, including those mediating chromosome synapsis and recombination. The results of Aim 3 will determine which functions of PRDMS in meiosis and gametogenesis require either its histone methyltransferase activity or its transcription-regulating KRAB domain. Recent results suggest that non-coding RNAs are among the transcriptional targets of PRDMS. In cooperation with goals of Projects B and C, this aim will define PRDMS-specific genomic sequence targets and functional clusters of sequences epigenetically marked and/or with transcription regulated by specific PRDMS domains and their relationship to PRDMS-dependent recombination hotspots. Together, the results of this project will complement the other Projects by setting PRDMS function into the well-defined sequence of meiotic chromosome events, more specifically resolving the molecular basis for its multiple roles, and contributing to understanding how PRDMS fits into the larger network of proteins that control meiosis and gametogenesis. An important facet of PRDMS biology addressed by this project is that PRDMS is a major determinant of fertility; the aberrant recombination and failed meiosis that occur in its absence can lead to sterility or birth defects in humans.