Adolescent idiopathic scoliosis associated <i>POC5</i> mutation impairs cell cycle, cilia length and centrosome protein interactions

Adolescent Idiopathic Scoliosis (AIS) is a spinal deformity that affects approximately 3 percent of human adolescents. Although the etiology and molecular basis of AIS is unclear, several genes such as POC5 have been identified as possible causes of the condition. In order to understand the role of POC5 in the pathogenesis of AIS, we investigated the subcellular localization of POC5 in cilia of cells over-expressing either the wild type (wt) or an AIS-related POC5 variant POC5A429V. Mutation of POC5 was found to alter its subcellular localization and to induce ciliary retraction. Furthermore, we observed an impaired cell-cycle progression with the accumulation of cells in the S-phase in cells expressing POC5A429V. Using immunoprecipitation coupled to mass spectrometry, we identified specific protein interaction partners of POC5, most of which were components of cilia and cytoskeleton. Several of these interactions were altered upon mutation of POC5. Altogether, our results demonstrate major cellular alterations, disturbances in centrosome protein interactions and cilia retraction in cells expressing an AIS-related POC5 mutation. Our study suggests that defects in centrosomes and cilia may underlie AIS pathogenesis.青少年特发性脊柱侧凸（Adolescent Idiopathic Scoliosis, AIS）是一种影响约3%青少年人群的脊柱畸形。尽管AIS的病因及分子基础尚未明确，但已有包括POC5在内的多个基因被鉴定为该病症的潜在致病因素。为阐明POC5在AIS发病机制中的作用，我们对过表达野生型（wild type, wt）或AIS相关POC5突变体POC5A429V的细胞，开展了其纤毛内POC5亚细胞定位的相关研究。研究发现，POC5的突变可改变其自身的亚细胞定位，并诱导纤毛收缩。此外，我们观察到表达POC5A429V的细胞存在细胞周期进程受损的情况，细胞出现S期蓄积。通过免疫沉淀（immunoprecipitation）联合质谱分析（mass spectrometry）技术，我们鉴定出POC5的特异性相互作用蛋白，其中绝大多数为纤毛与细胞骨架的组成成分。部分此类蛋白质相互作用会因POC5的突变发生改变。综上，我们的研究结果证实，携带AIS相关POC5突变的细胞会出现显著的细胞异常、中心体蛋白质相互作用紊乱及纤毛收缩。本研究提示，中心体与纤毛的功能缺陷可能是AIS发病机制的潜在基础。