The influence of tissue organization on the generation of TGF-ß signals and the function of stem cell niches in the Drosophila melanogaster germline.

这项拟议研究的目的是阐明组织如何通过控制细胞间信号的传播来塑造干细胞的生态位。以前在几个系统中的工作表明，壁龛和干细胞之间的黏附和信号传递过程在功能上是联系在一起的，而且有人提出，壁龛信号的紧密空间调节是通过假定的基于黏附的“干细胞壁龛突触”实现的，但从机械上讲，这种突触并没有很好的定义。我们将集中在果蝇生殖系上，其中BMP型转化生长因子-β生长因子DPP的信号有助于维持生殖系干细胞库的利基微环境。在雄性中，DPP信号被严格限制在那些与DPP源直接接触的生殖系细胞中。由于DPP可以在其他环境中通过许多细胞直径发出信号，突触样机制可能会限制BMP在NICE-GSC界面上的扩散。我们最近开发了基于GFP的BMP受体激活实时报告程序，这是第一次能够以亚细胞分辨率实时检测活跃的BMP受体群体。正如干细胞突触假说所预测的那样，我们可以证明，在苍蝇中，睾丸信号仅限于GSCs接触BMP分泌的壁龛细胞的小片。因此，在这个项目中，我们将使用苍蝇遗传学和细胞生物学方法来扰乱壁龛组织，并从功能上剖析这个信号突触。

The aim of the proposed study is to elucidate how tissue organization shapes stem cell niches by controlling the spreading of intercellular signals. Previous work in several systems has suggested that adhesion and signaling processes between niche and stem cells are functionally linked, and it has been proposed that the tight spatial regulation of niche signaling is achieved via a putative adhesion based “stem cell niche synapse” that however is mechanistically not well defined. We will focus on the Drosophila germ line, where signalling by the BMP type TGF-β growth factor Dpp contributes to the niche microenvironment that maintains the germline stem cell (GSC) pool. In the male the Dpp signal is tightly limited to those germline cells in direct contact with the Dpp source. Since Dpp can signal over many cell diameters in other contexts a synapse like mechanism may confine BMP spreading at the niche-GSC interface. We have recently developed GFP-based live reporters for BMP receptor activation that for the first time allow detection of the active BMP receptor population live and at subcellular resolution. As predicted by the stem cell synapse hypothesis we could show that in the fly testis signalling is confined to small patches where the GSCs contact the BMP secreting niche cells. In this project we will therefore use fly genetics and cell biological methods to perturb niche tissue organisation and functionally dissect this signalling synapse.