TTC蛋白质家族在纤毛发生中的功能及作用机理

Cilia are microtubule-based hair-like organelles present on nearly all vertebrate cells. Many studies in the last decade have indicated an essential role of cilia as sensors for extracellular signals and platforms for signal transduction.Defects in ciliogenesis lead to a series of genetic disorders, including polycystic kidneys disease (PKD)and Bardet-Biedl syndrome (BBS). In our previous studies, we established an in vitro mouse tracheal epithelial cell(MTEC) culture system, in which more than 80% of cells can be induced into multiciliated cells. To explore the molecular mechanism of ciliogenesis, we performed a DNA microarray screen to search for genes that are markedly upregulated during the MTEC differentiation. Besides many known cilia-related genes, hundreds of novel genes were discovered, including approximately 20 components of TTC protein family. Several TTC genes have been reported to associated with cilia-related diseases (ciliopathies), such as Bardet-Biedl synchrome related genes, BBS4 and BBS8. In this project, we will investigate the function and the molecular mechanism of the identified unknown TTC genes in ciliogenesis in various animal systems, such as zebrafish and knockout mice. Furthermore, we will also explore the relationship between TTC protein family and ciliopathies.

纤毛是广泛分布在动物体内的一种突出细胞表面的细胞器，在胞外环境感知和信号转导等方面发挥重要作用，已发现包括多囊肾、Bardet-Biedl综合症在内的多种遗传性疾病与纤毛病变相关。为了深入了解纤毛发生的分子机理及其与疾病的关系,在前期的研究中,我们建立了高效的纤毛细胞分化系统。利用基因芯片技术，我们对分化过程中变化显著的基因进行了筛选,除了众多已知纤毛相关基因,我们还得到了大量未知功能的基因,其中就包括二十多个TTC蛋白质家族成员。已有研究发现多个TTC蛋白与纤毛发生及其遗传疾病相关，如Bardet-Biedl综合症相关基因BBS4和BBS8。本项目将利用斑马鱼、哺乳动物细胞系及其小鼠等系统对筛选到的未知功能的TTC蛋白在纤毛发生上的功能及其分子机理进行深入的研究，并探索该蛋白质家族的功能以及这些基因与纤毛病变相关的遗传疾病之间的关系。

TPR（Tetratricopeptide repeat）结构域广泛分布于纤毛相关蛋白质中，但是对具有TPR结构域的蛋白质（Tetratricopeptide repeat containing proteins, 即TTC蛋白质）在纤毛中的功能系统性的研究还很缺乏。本项目通过分析不同分化阶段的小鼠气管上皮细胞的基因表达谱，发现了20个TTC蛋白质（其中10个已知，10个未知基因）在纤毛细胞分化过程中表达水平显著上调。斑马鱼中的研究发现敲低其中6个TTC蛋白质（TTC4，-9c，-25，-26，-36和-39c）会导致身体弯曲、脑积水和内脏左右不对称性紊乱等纤毛病表型，提示这6个基因可能与纤毛病相关。进一步的蛋白质互作实验表明这6个TTC蛋白质与纤毛内物质运输相关的IFT蛋白质复合物（intraflagellar transport protein complex）或BBSome复合物有相互作用，提示这些蛋白质可能参与纤毛内物质的运输。论文发表在PLoS One上。我们从中选择并着重研究了TTC26这个基因在纤毛中的功能，并制备了基因敲除小鼠，发现该基因的敲除会导致小鼠脑积水、骨骼及其牙齿发育异常。此外，我们利用哺乳动物多纤毛细胞，小鼠气管上皮体外分化系统，发现了一个在多纤毛分化过程中，介导中心粒扩增的主要结构摇篮体的首个核心组分Deup1并揭示其作用机理，相关论文发表在2013年的Nat Cell Biol上，并受到Science，Nat Cell Biol，F1000的评述。