PI3K-AKT信号通路介导的脂肪浸润在巨指（趾）症发生中的作用和调控机制

巨指（趾）症是由于脂肪组织过度增生导致的肢体异常肥大畸形，严重影响患者的外形及功能，常导致截肢的后果。我们前期对患者病变脂肪组织进行全基因组外显子测序，发现PIK3CA基因H1047R位点错义突变且磷酸化AKT水平明显上调，提示该突变激活了AKT信号通路。因此我们推测，PIK3CA点突变引起的AKT激活是导致巨指（趾）症发生的关键因素。尽管该突变曾在其它脂肪过度增生疾病中被报道，但致病机制不明。本研究拟扩大样本量验证PIK3CA在巨指症中的突变频率和类型；通过病变脂肪细胞特性研究，了解PI3K/AKT通路对脂肪细胞生物学行为的影响；然后以3T3-L1脂肪前体细胞系为模型，通过PIK3CA基因突变体过表达和阻断正反两个方向、体外和体内两个方面以及信号通路的多个水平，系统阐明PI3K/AKT通路在巨指症发生中的作用和机制；最后研究药物对疾病发生信号通路的抑制作用，为临床靶向治疗提供科学依据。

Macrodactyly is a congenital anomaly characterized by the enlargement of digits resulting from the overgrowth of adipose tissues. There is no effective treatment to cure the disease and the etiology is not known. We applied whole-exome sequencing to study the macrodactylous adipose tissue and identified a somatic mutation of PIK3CA (H1047R).Western blot shows that AKT phosphorylation is increased in the affected tissues, indicating activation of the PI3K-AKT pathway. We hypothesize that PIK3CA mutation-mediated AKT pathway plays a vital role in the development of macrodactyly. PIK3CA mutation has also been reported in diseases with adipose hyperplasia and some malignant tumors. In this study, we will confirm somatic mutations of PIK3CA and activation of the PI3K-AKT pathway in additional patients. The morphologic, molecular and cell differentiation properties of macrodactylous adipocytes will be studied to understand the impact of PIK3CA mutations. The 3T3-L1 pre-adipose cell line will be used as a cell model to investigate the effect and mechanism of PI3K/AKT signaling in macrodactyly, by overexpressing mutated PIK3CA, pathway blocking with various inhibitors and RNA interference. 3T3-L1 cell lines stably expressing PIK3CA mutations will be transplanted into nude mice, followed by examination of lipid formation and overgrowth. Rescue experiments using PI3K inhibitor LY294002 or mTOR inhibitor Rapamycin will be used to explore possible treatment of macrodactyly.