FGF-BMP-Wnt信号网络对神经干细胞周期和增殖分化的数字化调控

Niche factors can cross-talk and establish feedbacks, synergistic and antagonistic interactions to achieve a timely, precise and quantitative control of neural stem cell proliferation and differentiation. Abundant evidence suggests that the length of stem cell cycle may impact their differentiation propensities （proliferation versa differentiation） and lineage choices (neuron versa glia). However, the underlying molecular mechanisms remain poorly explored. In the present proposal, we have established an in vitro neural stem cell culture system to model the digitalization of neural stem cell cycle and differentiation activities. To do this, we have performed genomic analysis of the systems and selected a group of most essential and representative signaling (FGF/BMP/Wnt). Based on our preliminary results, we reason that the lengthening of stem cell cycle G1 phase will allow more time for the accumulation of oscillating fate determining transcription factors which in turn dictate stem cell differentiation propensities and choices. To test this, we will digitally manipulate the length of neural stem cells by combinations of major niche factors (FGF/BMP/Wnt) and/or modulating the level of intrinsic cell cycle regulating molecules (Cyclins and CDKs). We will then explore how the expression accumulations and dynamics of oscillating fate determining transcription factors within stem cell G1 phase may correlate with their differentiation propensities and choices. The success of this proposal will provide novel insight on how the digital control of neural stem cell fate choice may be achieved through precise and quantitative coordination of diverse signaling; furthermore, it will pave the scientific and technical foundations for further exploration of a potential causal relationship between the accumulation of oscillating master transcription factors within lengthening stem cell G1 phase and their differentiation propensities and choices.

微环境中的复杂信号网络可通过相互反馈、协同和拮抗，达到对神经干细胞增殖与分化的及时、精准的量化调控。已有研究提示细胞周期的长度可决定干细胞的分化倾向与潜能，但其机制不明，是目前干细胞研究的热点。本项目旨在建立可以精准量化调控静息激活和细胞周期的体外细胞培养体系，结合组学分析,确定关键的信号网络通路，模拟并解析生物体内的复杂信号通路对于干细胞细胞周期和命运决定的数字化调控机理。以前期数据为基础，我们提出新的调控假说：细胞G1期的延长将会导致振荡表达的转录因子的积累水平改变，从而调控干细胞的分化倾向与潜能。通过量化改变调控细胞周期的内外源因素，动态检测相关转录因子的表达水平和相应细胞周期状态的细胞分化倾向与潜能，对该假说进行验证。本课题的完成将为体内干细胞的命运精准量化调控提供新的思路，为进一步深入研究转录因子表达振荡与细胞周期长度在细胞分化倾向与命运决定中的因果关系打下坚实的理论和技术基础。

本项目的主要目标是建立具有代表性的体外数字化调控系统，揭示复杂信号通路调控神经干细胞细胞周期及后续分化命运的分子机制。经过三年的研究探索，我们建立了可逆性体外神经干细胞静息激活体系。并在此基础上建立了以三因子为基础的复杂信号通路的量化调控体系，对该体系进行了基因组和转录组的全面分析，提出了生物体量化调控发育和维持稳态的可能机制。同时我们提出细胞周期长度可通过影响转录因子在G1 期细胞的积累调控干细胞分化倾向与潜能的新假说。这一假说无需人为的调节转录因子的表达水平，而是通过上游信号通路或细胞周期相关的因子直接改变细胞周期的长度，继而影响干细胞的后续分化能力。通过我们的数据，这一假说已经基本证实，可为体内干细胞命运调控提供新的机制，也为干细胞相关疾病的治疗提供新的靶点和思路。课题相关的部分文稿正在起草中，有望在1年左右发表1-2篇专业期刊以上的文章。此外，部分相关的合作交流文章已经发表2篇，项目负责人作为第一作者的1篇，第二作者的1篇。