Mechanisms of stem cell specification in the male germline

项目总结/摘要 生殖细胞系提供了世代之间的永久细胞联系，在后生动物中， 男性对下一代的遗传贡献通过精子传递。因此， 精子（即精子发生）对于物种的连续性和多样性至关重要。 该项目旨在促进我们对发展起源的理解， 精子产生（即精子发生）谱系。特别是，它试图揭示一个细胞自主 触发驱动基础精原干细胞（SSC）库的形成， 在成年期精子发生和男性生育能力的连续性。在哺乳动物中，SSC库 已知在出生后的早期从生殖器前体的一个子集中产生 人口，但这一进程的基础机制严重不明确。的确，没有一个 迄今为止，已经确定分子对于该过程是必需的。 了解基础SSC库是如何从原生前体中构建的 在科学和临床上都很重要这一研究领域的进展有限，因为 一直缺乏详细调查这一进程的工具。在过去的几年里， 我们发现了由SSCs表达的基因（例如Id 4），并产生了多转基因细胞。 报告小鼠模型，通过胎儿和新生儿发育标记生殖细胞亚群。使用 这些工具，我们已经能够描述的动力学基础的建设， SSC池，确定该过程在新生儿发育的定义年龄点触发 (P0-3在小鼠中），并在单细胞水平上描绘转录组动力学。这些活动的成果 研究揭示了转录因子Msx 1的独特表达谱; 在P0时，基于轨迹的一个亚组的无性生殖群体中的诱导 来自scRNA-seq分析的预测注定成为SSC。本项目设计 确定时间Msx 1表达对SSC命运特化的效力，并探索 Msx 1在果蝇中的作用机制。预计结果将提供丰富的 我们可以从中定义如何在繁荣细胞亚群中触发SSC命运的信息 在新生儿的发育过程中。这些信息可能在临床和科学上有用， 了解男性不育的病因，并通过短暂的异位表达方法， 重新编程体细胞以采用SSC命运或使衰老或衰老的干细胞能力恢复活力， 不完善的SSC。

PROJECT SUMMARY/ABSTRACT The germline provides an eternal cellular link between generations and in metazoan a male's genetic contribution to the next generation is delivered via sperm. Thus, the genesis of sperm (i.e. spermatogenesis) is critical for the continuity and diversity of a species. This project is designed to advance our understanding of the developmental origins of the sperm producing (i.e. spermatogenic) lineage. In particular, it seeks to uncover a cell autonomous trigger driving formation of the foundational spermatogonial stem cell (SSC) pool which is required for continuity of spermatogenesis and male fertility in adulthood. In mammals, the SSC pool is known to arise in early postnatal life from a subset of the prospermatogonial precursor population but the mechanism underpinning the process is grossly undefined. Indeed, no single molecule as has been identified, to date, to be obligatory for this process. Understanding how the foundational SSC pool is built from prospermatogonial precursors is scientifically and clinically important. Progress in this area of study has been limited because the tools for investigating the process in fine detail have been lacking. Over the past several years, we discovered genes that are expressed by SSCs (e.g. Id4) and generated multi-transgenic reporter mouse models to label germ cell subsets through fetal and neonatal development. Using these tools, we have been able to describe the kinetics underlying the building of the foundational SSC pool, determine that the process is triggered at a defined age point in neonatal development (P0-3 in mice), and profile transcriptome dynamics as the single cell level. Outcomes of these studies uncovered a unique expression profile for the transcription factor Msx1; temporal induction in a subset of the prospermatogonial population at P0 that based on trajectory predictions from scRNA-seq analyses are fated to become SSCs. The current project is designed to define the potency of temporal Msx1 expression on SSC fate specification and explore the mechanism of action for Msx1 in prospermatogonia. Results are expected to provide a wealth of information from which we can define how SSC fate is triggered in a subset of prospermatogonia during neonatal development. This information may be clinically and scientifically useful for understanding the etiology of male infertility, and through transient ectopic expression approaches to reprogram somatic cells to adopt an SSC fate or rejuvenate stem cell capacity in aged or imperfect SSCs.