Elucidating the Role of TCF21+ Mesenchymal Cells in Testis Tissue Homeostasis and Regeneration

摘要 男性的生育能力取决于生殖激素和成熟精子的成功产生， 这需要生殖细胞、支持体细胞和下丘脑-垂体的协同活动。 轴心。参与睾丸这些过程的细胞类型的多样性在很大程度上是由组织学定义的， 但我们对体细胞种群的分子理解在很大程度上受到转基因株系可用性的限制。 因此，为了实现对体细胞室和分子细胞类型的公正分析，我有 将单细胞RNA-seq应用于成年小鼠睾丸。经鉴定的~5000个单细胞的转录组分析 所有主要的体细胞类型，以及以前不为人知的间质细胞群(TCF21+细胞)。聚类 主成分分析表明，新的细胞群与肌样和间质细胞有关 细胞。对该群体的标记基因分析表明该群体为间充质干细胞。 (MSC)。在其他器官中，间充质干细胞以其再生和免疫调节能力而闻名，但 这种细胞群能够支持成年睾丸中的睾丸组织的动态平衡和再生， 或作为肌样细胞或间质细胞的起源，目前尚不清楚。因此，这项建议旨在 探讨TCF21+细胞在胚胎和成人睾丸中的功能作用。根据我的初步数据和 先前的遗传学研究表明TCF21在睾丸分化和发育中起关键作用，即 假设TCF21+细胞是肌样细胞和间质细胞的前体细胞，并作为体细胞的储备干细胞 成人睾丸中的细胞。为了解决这些问题，我将使用基因谱系追踪的组合， 免疫组织化学和功能鉴定，体内靶向细胞消融。这些研究将 阐明睾丸间质细胞的发育和动态平衡功能，并将提供新的 储备体细胞干细胞群体的证据，这可能被用来提供新的治疗方法 雄激素低减和/或不孕症患者的治疗方法。此外，这项工作的完成将 为我提供关键的科学、技术和医学培训，如我的培训计划中所述，这将是 作为一名研究内科疾病内在和外在调节的内科科学家，取得成功的基础 精子发生和男性生育能力。

Abstract Male fertility is dependent on the successful production of both reproductive hormones and mature sperm, which requires the concerted activity of germ cells, supporting somatic cells, and the hypothalamic-pituitary axis. The diversity of cell types involved in these processes in the testis has largely been defined histologically, but our molecular understanding of somatic populations is largely limited by the availability of transgenic lines. Therefore, to achieve an unbiased analysis of the somatic compartment and molecular cell types, I have applied single cell RNA-seq to the adult mouse testis. Transcriptome analysis of ~5000 single-cells identified all major somatic cell types, and a previously unappreciated interstitial cell population (Tcf21+ cells). Clustering and principle component analyses suggest that the novel cell population is related to both myoid and Leydig cells. Marker gene analysis of this population is consistent with this population being a mesenchymal stem cell (MSC). In other organs, MSCs are known for their regenerative and immunomodulatory potential, but whether this cell population is capable of supporting testicular tissue homeostasis and regeneration in the adult testis, or serving as the cell of origin myiod or Leydig cells, remains unknown. Therefore, this proposal aims to explore the functional role of Tcf21+ cells in the embryonic and adult testis. Based on my preliminary data and previous genetic studies demonstrating a key role for Tcf21 in testis differentiation and development, I hypothesize that Tcf21+ cells are precursors for myoid and Leydig cells, and serve as a reserve somatic stem cell in the adult testis. To address these questions, I will use a combination of genetic lineage tracing, immunohistochemical and functional characterization, and in vivo targeted cell ablation. These studies will elucidate the development and homeostatic function of interstitial cells in the testis, and will provide new evidence for a reserve somatic stem cell population, which could be used to inform new therapeutic approaches for patients with hypoandrogenism and/or infertility. Additionally, completion of this work will provide me with critical scientific, technical, and medical training, as outlined in my training plan, which will be foundational for a successful career as a physician scientist studying the intrinsic and extrinsic regulation of spermatogenesis and male fertility.