小胶质细胞是驻扎在中枢神经系统的巨噬细胞，它们不仅在生理状态下对中枢神经系统的发育和稳态的维持具有重要的作用，而且在病理状态下还与多种神经系统疾病，比如阿尔兹海默综合症等的诱发与恶化有着紧密的联系。研究人员发现，无论小鼠和斑马鱼，早期小胶质细胞的发育都受到ETS家族转录因子PU.1的严格调控。然而由于PU.1缺陷导致小胶质细胞的完全缺失，因此我们对PU.1在小胶质细胞稳态维持中的作用却不得而知。在我们的前期工作中，我们通过CRISPER/Cas9介导的非同源末端连接的基因敲入手段建立了pu.1条件性敲除斑马鱼品系，并发现小胶质细胞中单独敲除pu.1对其后续的数量维持没有影响。于此同时，当在spi-b突变体中对pu.1进行条件性敲除后，小胶质细胞的数量则在短时间内发生了明显的减少。因此，本项目中，我们将针对这一现象进一步探究Pu.1和Spi-b缺陷后小胶质细胞数量减少的细胞学基础和分子机制。

Microglia are a group of specified macrophages residing in central nervous system (CNS) and play pivotal roles in the regulation of neuronal development and maintaining the homeostasis of CNS in physiological condition. Furthermore, in pathological conditions, microglia are also highly associated with the onset and progression of many neuronal disorders, such as Alzheimer’s disease, Parkinson disease and multiple sclerosis (MS). In mice and zebrafish, it was documented that early development of microglia is tightly controlled by the ETS family transcription factor PU.1. However, due to the complete loss of microglia/macrophages in PU.1-deficient mouse or zebrafish embryos, our understanding of the role of Pu.1 in the maintenance of microglia pool after its establishment is still lacking. In our previous work, we generated a pu.1 conditional knockout allele pu.1KI via Non-homologous end jointing (NHEJ) mediated knockin method. Phenotypical analysis revealed that conditional depletion of Pu.1 in microglia had no effect on their maintenance. However, when we inactivated Pu.1 in the microglia of spi-b mutant, their number rapidly declined. Hence, in this project, we are planning to figure out the cellular basis underlying the reduction of microglia number in this process and further investigate the genetic interactions and molecular mechanism of Pu.1 and Spi-b in the regulation of microglia maintenance. Successful fulfillment of this project will not only broaden our knowledge on the functions of Pu.1 and Spi-b, but also provide new insights into the understanding of molecular mechanisms underlying microglia maintenance, which could hopefully contribute to the intervention and treatment of microglia-related neuronal disorders.