1Division of Experimental Medicine, McGill University, Montréal.
2Department of Pediatric Surgery, Division of Neurosurgery, Montreal Children's Hospital, McGill University Health Centre Research Institute, Montréal.
J Neurosurg Pediatr. 2023 Mar 10;31(6):584-592. doi: 10.3171/2023.1.PEDS22287. Print 2023 Jun 1.
The aim of this study was to characterize a novel pathogenic variant in the transient receptor potential vanilloid 4 (TRPV4) gene, causing familial nonsyndromic craniosynostosis (CS) with complete penetrance and variable expressivity.
Whole-exome sequencing was performed on germline DNA of a family with nonsyndromic CS to a mean depth coverage of 300× per sample, with greater than 98% of the targeted region covered at least 25×. In this study, the authors detected a novel variant, c.496C>A in TRPV4, exclusively in the four affected family members. The variant was modeled using the structure of the TRPV4 protein from Xenopus tropicalis. In vitro assays in HEK293 cells overexpressing wild-type TRPV4 or TRPV4 p.Leu166Met were used to assess the effect of the mutation on channel activity and downstream MAPK signaling.
The authors identified a novel, highly penetrant heterozygous variant in TRPV4 (NM_021625.4:c.496C>A) causing nonsyndromic CS in a mother and all three of her children. This variant results in an amino acid change (p.Leu166Met) in the intracellular ankyrin repeat domain distant from the Ca2+-dependent membrane channel domain. In contrast to other TRPV4 mutations in channelopathies, this variant does not interfere with channel activity as identified by in silico modeling and in vitro overexpression assays in HEK293 cells.
Based on these findings, the authors hypothesized that this novel variant causes CS by modulating the binding of allosteric regulatory factors to TRPV4 rather than directly modifying its channel activity. Overall, this study expands the genetic and functional spectrum of TRPV4 channelopathies and is particularly relevant for the genetic counseling of CS patients.
本研究旨在研究瞬时受体电位香草素 4（TRPV4）基因中的一种新型致病性变异，该变异导致家族性非综合征性颅缝早闭（CS），具有完全外显率和可变表达性。
对一个非综合征性 CS 家系的生殖系 DNA 进行全外显子组测序，平均深度覆盖每个样本 300×，靶向区域大于 98%的覆盖率至少为 25×。在本研究中，作者检测到一个新的变异，c.496C>A，仅在四个受影响的家族成员中发现。该变异使用来自 Xenopus tropicalis 的 TRPV4 蛋白结构进行建模。使用在过表达野生型 TRPV4 或 TRPV4 p.Leu166Met 的 HEK293 细胞中进行的体外测定来评估该突变对通道活性和下游 MAPK 信号传导的影响。
作者在 TRPV4 中鉴定出一种新型、高度外显的杂合变异（NM_021625.4：c.496C>A），该变异导致母亲及其三个孩子的非综合征性 CS。该变异导致细胞内环状重复结构域中氨基酸改变（p.Leu166Met），远离 Ca2+依赖性膜通道结构域。与其他 TRPV4 通道病中的突变不同，该变异不会像通过计算机建模和在 HEK293 细胞中进行的体外过表达测定所确定的那样干扰通道活性。
基于这些发现，作者假设该新型变异通过调节变构调节因子与 TRPV4 的结合而不是直接修饰其通道活性来引起 CS。总体而言，本研究扩展了 TRPV4 通道病的遗传和功能谱，对 CS 患者的遗传咨询尤为重要。
