Somatic frameshift mutation in PIK3CA causes CLOVES syndrome by provoking PI3K/AKT/mTOR pathway

Wei Yan,Wen Qin,Lin Ma,Xingyuan Jiang,Ran Mo,Zhimiao Lin,Huijun Wang,Bin Zhang

doi:10.1186/s41065-021-00184-y

Abstract

BackgroundCLOVES syndrome (OMIM# 612918) is a rare overgrowth disorder resulted from mosaic gain-of-function mutations in the PIK3CA gene. All the reported CLOVES-associated PIK3CA mutations are missense mutations affecting certain residues. We aim to investigate underlying mutation and its pathogenicity in a patient with CLOVES syndrome and to evaluate the inhibitory effects of the PI3K/AKT/mTOR pathway inhibitors.ResultsWe performed whole-exome sequencing (WES) and Sanger sequencing to detect underlying somatic mutations in the skin lesion of the patient. Quantitative real-time PCR (qRT-PCR) was employed to evaluate the mRNA abundance of PIK3CA in the patient’s skin lesion. AKT phosphorylation level assessed by immunoblotting of lysates from transiently transfected cells was performed to evaluate the PIK3CA mutations and inhibitory effects of PI3K/AKT/mTOR pathway inhibitors. A somatic frameshift mutation c.3206_3207insG (p.X1069Trpfs*4) in PIK3CA was identified in the genomic DNA extracted from the vascular malformation sample of the patient. This mutation affects the canonical stop codon of PIK3CA (NM_006218.4) and is predicted to produce a prolonged protein with four additional residues. qRT-PCR demonstrated that the mRNA expression levels of the patient’s affected skin tissue were comparable compared to the normal control. In vitro studies revealed that p.X1069Trpfs*4 mutant exhibited increased AKT phosphorylation significantly to that of the wildtype, which could be inhibited by PI3K/AKT/mTOR pathway inhibitors.ConclusionsWe have identified the first frameshift mutation in PIK3CA that causes CLOVES syndrome, which was confirmed to overactive PI3K/AKT/mTOR pathway by transient transfection assays. We also provided more evidence of ARQ092 to be a potential therapeutic option for PROS in vitro.

Highlights

CLOVES syndrome (OMIM# 612918) is a rare overgrowth disorder resulted from mosaic gain-of-function mutations in the PIK3CA gene
With the acti‐ vating signals of receptor tyrosine kinase (RTK) or G‐protein coupled receptor (GPCR), p85 relieve the inhi‐ bition of p110 and Class IA Phosphatidylinositol 3‐kinases (PI3Ks) are recruited to the plasma membrane
In this study, we reported a patient with CLOVES syndrome caused by a somatic frameshift mutation c.3206_3207insG in PIK3CA which results in gain of function by provoking the PI3K/AKT/Mammalian target of rapamycin (mTOR) pathway

Summary

Introduction

CLOVES syndrome (OMIM# 612918) is a rare overgrowth disorder resulted from mosaic gain-of-function mutations in the PIK3CA gene. We aim to investigate underlying mutation and its pathogenicity in a patient with CLOVES syndrome and to evaluate the inhibitory effects of the PI3K/AKT/mTOR pathway inhibitors. Phosphatidylinositol 3‐kinases (PI3Ks) are a family of lipid kinases involved in the regulation of multiple cel‐ lular processes such as cell proliferation, differentiation, apoptosis, motility, and metabolism. It can be divided into three classes (Class I, II, III), and Class I can be fur‐ ther subdivided into Class IA and Class IB. PIP3 acted as a second messenger, which leads to the phosphorylation of AKT at residue Thr308 and Ser473 respectively. For fully AKT activation, the phos‐ phorylation status of AKT (Ser473 and Thr308) is neces‐ sary, which leads to the overactivation of the PI3K/AKT/ mTOR pathway [1,2,3]

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