Lin28/let-7信号轴调控牙乳头细胞分化影响牙本质发育的机制研究

牙本质的形成依赖由牙乳头细胞分化而来的成牙本质细胞分泌基质并介导矿化。牙乳头细胞成牙本质向分化是牙本质形成的关键过程，miRNA在其中有重要作用。Let-7是牙乳头细胞中高表达的miRNA家族，其形成过程受RNA结合蛋白Lin28抑制，Lin28同时也是let-7的靶基因，二者构成Lin28/let-7信号轴。本课题组前期研究发现Lin28和let-7在小鼠牙发育过程中有时空性特征，提示其可能在牙乳头细胞成牙本质向分化中发挥作用，但具体机制不详。本项目拟研究Lin28和let-7在牙本质发育过程中的时空表达特点；运用CRISPR激活系统、miRNA海绵、转基因小鼠等技术探索该信号轴在牙乳头细胞成牙本质向分化过程中的作用；应用二代测序筛选靶基因，揭示该信号轴影响牙本质形成的机制。本研究将加深对牙本质发育的认识，为探索遗传性牙本质发育不全等病因，拓展牙髓-牙本质复合体损伤修复相关研究奠定基础。

Dentin formation is achieved by odontoblasts, a special type of terminally differentiated cells lying on the outer wall of dental pulps. They originate from dental papilla cells at the late bell stage of tooth development. The cell fate determination of dental papilla cells is responsible for giving rise to odontoblasts, which is a key process during dentin formation. A number of studies have documented the significance of miRNAs in tooth development. Let-7 is a family of miRNAs enriched in dental papilla cells. The let-7 miRNAs’ biogenesis is inhibited by the RNA-binding protein Lin28, which meanwhile is also a target gene of let-7. These two together constitute a bi-stable switch, Lin28/let-7 axis, who contributes extensively to the maintenance of cell identity and onset of cell differentiation. Our pilot studies have unveiled that Lin28 and let-7 possess certain spatio-temporal expression pattern during mouse tooth development, and their expression level is anti-correlated, implicating their involvement in odontogenic differentiation of dental papilla cells. However, the specific role and underlying mechanism remains unknown. This project aims to investigate the spatio-temporal expression pattern of Lin28 and let-7; to decipher the role of Lin28/let-7 axis in the odontogenic differentiation of dental papilla cells with CRISPR activation, miRNA sponge, transgenic mice etc.; and to probe deeply into the intrinsic mechanism by utilizing next-generation sequencing, RNAseq, to screen for target genes and to predict and reveal potential downstream signaling pathway. Thus, this project will further the understanding of dentin development, facilitate the etiological exploration of dentin-related diseases, like dentinogenesis imperfecta and dentin dysplasia, and favor the therapeutic application of pulp-dentin complex regeneration.