Longitudinal imaging of stem cell coordination and cross-regulation in the testis niche

果蝇睾丸的正常功能和精子的持续产生需要精致的 两个常驻干细胞群体-生殖系干细胞（GSC）和 体细胞囊肿干细胞生殖细胞分化需要每一个GSC子细胞（a 成角细胞，或Gb）完全被包囊的两个子体包裹或包囊 造血干细胞睾丸龛协调这两个细胞的子细胞的产生。 通过对GSC施加细胞动力学延迟并需要细胞接触， 与包囊细胞结合，以触发胞质分裂的最后一步--分裂。 有趣的是，在细胞动力学暂停的长度上存在显著的变异性（30%至75%）。 细胞周期）。为了使系统在三电池单元一致形成的情况下实现鲁棒性， 停顿长度的可变性表明停顿、包囊形成和触发必须能够 每个步骤补偿其他步骤定时的变化。这预示着大量的交叉- 两种干细胞谱系之间的对话，以监测增殖率，干细胞数量和 胞质分裂时间先前的研究表明，在增殖中只有很小程度的协调， niche事实上，我们的分析显示，在这些细胞之间缺乏任何显著的有丝分裂同步， GSC及其侧翼的CySC，没有证据表明CySC侧翼相同的GSC， 有丝分裂协调。因此，我们推测这不是有丝分裂，而是改良的GSC胞质分裂 结合串扰和监测两种干细胞之间的子细胞数量 群体，这产生了一个强大的系统，以协调子细胞从小生境释放。 我们的反馈模型预测胞质分裂时间的缺陷会影响增殖， 增殖或干细胞数量的变化会影响胞质分裂时间。在这里，我们将 直接评估Gb包囊化和脱囊化之间的协调程度， 同时成像两个干细胞群体。然后我们将确定共同的程度- 调节和两个干细胞谱系之间的串扰，以确定潜在的 确保有力成果的机制

Proper function of the Drosophila testis and consistent production of sperm requires exquisite coordination between two resident stem cell populations—the germline stem cells (GSCs) and the somatic Cyst Stem Cells. Germ cell differentiation requires that every one GSC daughter (a gonialblast, or Gb) is completed encased or encysted by precisely two daughters of the Cyst Stem Cell lineage. The testis niche coordinates production of daughter cells from these two stem cell populations by imposing a cytokinetic delay on the GSCs and requiring cell contact with encysting cells in order for abscission, the final step of cytokinesis, to be triggered. Interestingly, there is significant variability in the length of the cytokinetic pause (30 to 75% of the cell cycle). For the system to achieve robustness with a three-cell unit consistently formed, the variability in pause length suggests that the pause, encystment and trigger must be capable of each compensating for changes in timing of the other steps. This predicts substantial cross- talk between the two stem cell lineages to monitor proliferation rates, stem cell numbers and cytokinesis timing. Prior studies revealed only a small degree of coordination in proliferation in the niche. In fact, our analysis showed a lack of any significant mitotic synchrony between GSCs and their flanking CySCs and no evidence that CySCs flanking the same GSC were mitotically coordinated. Thus, we hypothesize that it is not mitosis, but modified GSC cytokinesis combined with cross-talk and monitoring of daughter cell numbers between the two stem cell populations, that generates a robust system to coordinate daughter cell release from the niche. Our feedback model predicts that defects in cytokinesis timing would affect proliferation while changes in proliferation or stem cell number would affect cytokinesis timing. Here, we will directly assess the degree of coordination between Gb encystment and abscission by simultaneous imaging of both stem cell populations. We will then determine the degree of co- regulation and cross talk between the two stem cell lineages to identify the underlying mechanisms that ensure a robust outcome