Investigating epigenetic inheritance patterns and mechanisms during asymmetric division of Drosophila female germline stem cells

表观遗传修饰提供了一种重要的机制，通过这种机制，含有相同基因组的细胞可以 采用并维护不同的小区标识。这些机制对于维持干细胞库至关重要 它可以分化和补充在体内平衡、损伤和衰老过程中丢失的组织。为了维持干细胞 池，不对称细胞分裂（ACD）发生在一个子细胞成为自我更新的干细胞， 另一个女儿继续分化。这种平衡的破坏可能是灾难性的，导致缺陷 从癌症到退行性疾病。尽管它很重要，但人们对它是如何以及如何产生的知之甚少。 在ACD过程中，干细胞的表观遗传信息可以在其两个子细胞之间分配。项目 这里提出的将（1）允许可视化的表观遗传信息包含在基因特异性位点上， 在ACD过程中分离姐妹染色单体和（2）描述了忠实的顺式和反式元件 两个子细胞之间的表观遗传学上不同的染色单体的分离。 核小体是表观遗传控制的主要参与者，它是组蛋白的八聚体， 与DNA相互作用，并具有N-末端“尾巴”，可以被广泛修饰以影响基因表达。是 已知组蛋白的年龄与其携带的表观遗传修饰类型相关。因此可能 ACD的子体可能通过继承“旧”组蛋白和“新”组蛋白而获得不同的命运 对维持干细胞状态或促进分化很重要的基因。果蝇生殖系 允许在体内以单细胞分辨率观察不对称生殖系干细胞（GSC）分裂， 这是一个很好的研究ACD子代之间组蛋白分离的系统。目前实验室的数据显示， 确实在有丝分裂的GSC中发现了非重叠的新旧组蛋白信号的显著区域。探讨 在这些区域，一种新的成像技术已经开发出来。简而言之， 应用含有“干性”或分化基因的基因来确定特定基因是否优先 与新旧组蛋白的关系此外，这些探针将与针对特异性抗体的抗体一起使用。 组蛋白修饰，以揭示更新的干细胞子细胞和 女儿注定要在ACD中分化。现场和固定成像将阐明这两个顺式元件的动态 染色单体和有丝分裂机制的反式调节因子，以确定它们在姐妹染色单体中的作用。 GSC ACD期间的染色单体识别和分离。 这些结果将揭示在ACD期间如何建立基因特异性表观遗传控制，并提供 一个时空图的分子机制和细胞事件参与忠实地分离， 信息.这些方法可以广泛应用于其他生物体和细胞谱系，这将增强生物学特性。 研究ACD关键过程的能力。这里生成的数据和技术将显著影响 干细胞和染色质生物学领域的基础知识。

Epigenetic modifications provide essential mechanisms by which cells containing identical genomes can adopt and maintain different cell identities. These mechanisms are crucial for maintaining pools of stem cells that can differentiate and replenish tissue lost during homeostasis, injury, and aging. To maintain the stem cell pool, asymmetric cell division (ACD) occurs where one daughter cell becomes a self-renewed stem cell and the other daughter goes on to differentiate. Disruption of this balance can be disastrous, leading to defects ranging from cancer to degenerative diseases. Despite its importance, little is known about which and how the epigenetic information of the stem cell could be distributed between its two daughters during ACD. The project proposed here will (1) permit visualization of the epigenetic information contained at gene-specific loci on segregating sister chromatids during ACD and (2) describe the cis and trans elements involved in the faithful segregation of the epigenetically distinct chromatids between the two daughter cells. A major player in epigenetic control is the nucleosome, an octamer of histone proteins that intimately interacts with DNA and has N-terminal `tails' that can be extensively modified to affect gene expression. It is known that the age of a histone is correlated with the types of epigenetic modifications it carries. Thus, it may be possible that the daughters of an ACD may acquire their different fates by inheriting `old' versus `new' histones at genes important for maintaining the stem cell state or promoting differentiation. The Drosophila germline permits visualization of asymmetric germline stem cell (GSC) division at single-cell resolution in vivo, making it a great system to study histone segregation between the daughters of an ACD. Current data in the lab has indeed found significant regions of non-overlapping old and new histone signals in mitotic GSCs. To investigate these regions, a new imaging technique has been developed. In short, fluorescent probes targeting loci containing either `stemness' or differentiation genes are applied to determine if a particular gene is preferentially associated with old versus new histones. Further, these probes will be used with antibodies against specific histone modifications to reveal the epigenetic differences between the renewed stem cell daughter and the daughter destined to differentiate in ACD. Live and fixed imaging will elucidate the dynamics of both cis elements on the chromatids and trans regulatory factors on the mitotic machinery to determine the roles they play in sister chromatid recognition and segregation during GSC ACD. The results will reveal how gene-specific epigenetic control is established during ACD as well as provide a spatiotemporal map of the molecular machinery and cellular events involved in faithfully segregating that information. These methods can be widely applied to other organisms and cell lineages, which will enhance the capacity to study the crucial process of ACD. The data and techniques generated here will significantly impact fundamental knowledge in the fields of stem cell and chromatin biology.