FMRP参与pre-mRNA选择性剪接调控机制及其在神经发育和突触功能调节中的作用

Fragile X mental retardation protein (FMRP) is involved in the regulation of gene expression that participates in neural development and synaptic function. FMRP dysfunction is associated with fragile X syndrome and other several neurodevelopment disorders. It has been demonstrated that alternative splicing of precursor mRNA (pre-mRNA) generates different protein isoforms which play critical roles in the regulation of brain development and related diseases. However, the relationship between FMRP and alternative splicing has not been reported till now. Using Co-IP experiment, our previous study indicated an interaction between FMRP and RBM14, an alternative-splicing-related protein. We further demonstrated that this interaction altered the ratio of several genes’ mRNAs subtypes and protein isoforms, which then affected the dendrite outgrowth in Neuro-2a cells under neuronal differentiation. We speculate that FMRP might be involved in the regulation of neuronal development and brain function through participating in the alternative pre-mRNA splicing. This project will identify FMRP-associated genes and analyze the alternative-splicing sites by comparing the splicing events in the brain of Fmr1 knockout and wildtype mice, and then analyze the regulatory factors involved in the FMRP-associated alternative splicing. We further explore the roles of protein isoforms in dendritic development of hippocampal neurons and synaptic function. This study will uncover the potential mechanism of FMRP in regulating alternative splicing and its role in the regulation of neuronal development and synaptic function, which should help to define the relationship between the FMRP-associated alternative splicing and neurodevelopmental disorders.

脆性X智力低下蛋白（FMRP）参与基因表达调控，调节神经发育和突触功能，与脆性X综合征等多种疾病密切相关。目前已证实前体mRNA（pre-mRNA）选择性剪接产生的不同蛋白亚型在调控脑发育及相关疾病中发挥重要作用，但其与FMRP的关系尚未见报道。本项目前期实验通过Co-IP筛选首次发现FMRP与一种选择性剪接相关RBM14蛋白相互作用，并证实这种相互作用影响到其他基因mRNAs亚型比例及细胞突起的生长，提示FMRP很可能通过参与pre-mRNA选择性剪接过程来调节神经元发育及功能。本项目将比较FMRP正常及缺失小鼠海马组织中选择性剪接的差异，鉴定FMRP调控的靶基因及剪接位点的序列特征，分析FMRP调控选择性剪接过程的调控因素及不同蛋白亚型对海马神经元树突发育及突触功能的影响，以揭示FMRP参与选择性剪接调控的机制及其在神经元发育及突触功能调节中的作用，探索其与神经发育障碍疾病的相关性。

脆性X智力低下蛋白(FMRP)与脆性X综合征（FXS）密切相关，通过与大脑内其他RNA结合蛋白相互作用，调控基因表达，发挥重要作用。本研究首次证实FMRP通过与选择性剪接相关蛋白RBM14结合，参与pre-mRNA选择性剪接过程，而且FMRP表达改变所导致的部分基因选择性剪接异常可影响细胞突起生长。FMRP缺失所导致的异常选择性剪接的基因与多种生物学过程及神经功能密切相关，包括调节神经发育与突触可塑性。此外，发现FMRP主要位于下丘脑弓状核，FMRP的缺失改变了下丘脑的蛋白质组学特征，其中MAP1B蛋白的增加最为显著。增加的MAP1B主要位于弓状核内，并且AgRP水平显著降低。进一步证明FMRP缺失可以通过上调MAP1B表达诱导AgRP水平下降，这可能与食物摄取量和体重减少有关。这些研究为进一步揭示FXS的发病机制提供新思路。