P4HB基因新突变导致成骨不全Cole-Carpenter综合征的分子机制研究

Osteogenesis imperfect (OI) is a hereditary bone disease of a single gene mutation characterized by increased bone fragility. Nowadays, most virulence genes are discovered related to the synthesis of collagen type I, osteoblast differentiation and bone mineralization. The exact molecular mechanism of the recent discovery of the specific type OI called cole-carpenter syndrome (CCS) which is caused by the P4HB gene mutation is still unclear. In our previous study on the OI patients by using second-generation sequencing, we detected that 1 CCS patients of P4HB new heterozygous mutation of p.C400R. The loci is highly conservative in various species. The protein structure shows that the site is located in the center of the reaction of the gene encoding protein disulfide isomerase. We hypothesized that the apoptosis induced by endoplasmic reticulum stress may be the key to the P4HB mutation resulted in CCS. Our research group intends to establish a P4HB-C400R knock-in mouse model to investigate the phenotype and function of skeletal resulting from this mutation. At the same time, skin fibroblasts of the patient would be cultured to study the changes of the function of collagen type I. The somatic cells would be reprogrammed to induced pluripotent stem (iPS) cells and would be induced to differentiate into osteoblasts and bone tissue. We would observe the differentiation process and the expression of stress pathway protein in endoplasmic reticulum of osteoblasts and bone tissue to verify the exact molecular mechanism of P4HB mutation. This study will provide a new target for the development of effective drugs for OI.

成骨不全（OI）是一种以骨脆性增加为主要特征的单基因遗传骨病。目前发现的致病基因多与Ⅰ型胶原的合成、成骨细胞分化及骨矿化相关。最近发现的P4HB基因突变导致的OI特殊类型Cole-carpenter综合症（CCS），其确切分子机制不清。我们前期对OI患者二代测序发现1例P4HB基因新杂合突变p.C400R导致的CCS。该位点高度保守，位于基因所编码的二硫键异构酶蛋白的反应中心。我们推测内质网应激诱导的成骨细胞凋亡可能是P4HB突变致CCS的关键。本课题拟构建P4HB基因C400R敲入小鼠模型，研究该突变导致的骨骼表型和功能，同时培养患者皮肤成纤维细胞，研究Ⅰ型胶原功能改变；重编辑体细胞为诱导多能干（iPS）细胞，诱导其分化为成骨细胞和骨组织，通过观察其分化及内质网应激通路蛋白的表达，以证实P4HB突变之确切分子机制。本研究将为研发治疗OI的有效药物提供新靶点。