表观遗通路及Hox基因在调控动物机体发育过程中起到了重要作用，但是关于其在干细胞干性以及组织稳态维持中的功能还知之甚少。表观遗传因子如何通过调控Hox基因表达在干细胞干性及组织稳态维持中发挥功能是一个重要的生物学问题。本项目以遗传筛选为切入点，以果蝇精巢为研究系统，发现表观遗传因子PcG的PRC1复合物的核心因子Polycomb（Pc）特异性的在果蝇精巢CySC细胞中发挥功能，调控了CySC细胞数目、GSC细胞身份维持及精巢的组织稳态；其功能依赖于PRC2复合物以及PRC1复合物的另一核心组分Sce；而Pc在CySC细胞中是通过调控Hox家族Abd-B基因的表达而实现其功能。在项目支持下，我们将深入揭示Pc调控Abd-B表达进而调控CySC细胞干性、GSC身份维持以及精巢稳态的机制及功能，阐明表观遗传与Hox基因在精巢稳态维持中的调控网络，为最终理解组织稳态维持调控机制提供坚实的理论基础。

Hox genes and epigenetic pathway play a fundamental role in regulating animal development. However, less is known about their functions on homeostasis maintenance in tissue and adult stem cells. It is a very important fundamental biology question that how epigenetic pathway controls tissue and stem cell homeostasis maintenance by regulating Hox gene expression. In this project, we found that the repression of an important axial Hox gene, Abdominal-B (Abd-B), in cyst stem cells (CySCs) is essential for the homeostasis and cell identity maintenance in adult Drosophila testis. Derepression of Abd-B in CySCs disrupts the proper self-renewal of both germline stem cells (GSCs) and CySCs, and leads to an excessive expansion of early stage somatic cells, which originate from both lineages. We further demonstrate that canonical Polycomb (Pc) and functional pathway of Polycomb group (PcG) proteins are responsible for maintaining the germline cell identity non-autonomously via repressing Abd-B in CySCs in adult Drosophila testis. In the future study, we will further focus on the molecular mechanism and biological function of how Pc and Abd-B regulate tissue and stem cell homeostasis maintenance in Drosophila testis, as well as the network of these two pathways in regulating stem cell and tissue homeostasis.