Plastic Surgery Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, 100032, China.
Affiliated Hospital of Weifang Medical University, Shandong, 261031, China.
Int J Pediatr Otorhinolaryngol. 2020 Dec;139:110488. doi: 10.1016/j.ijporl.2020.110488. Epub 2020 Nov 7.
Microtia is defined as a congenital malformation characterized by a small, abnormally shaped auricle, with atresia or stenosis of the auditory canal. This study investigated a mutation of the cytochrome P450, family 26, subfamily A, polypeptide 1(CYP26A1) gene, which is considered important in craniofacial development, in a family affected with microtia.
Whole-exome sequencing (WES) was performed on the proband and his family members to identify disease-associated variants. Computational predictions of the altered protein were analyzed using several bioinformatics tools. The wild-type (WT) and mutant forms of CYP26A1 cDNA were transfected into human embryonic kidney cells, and the mRNA and protein levels were compared using quantitative polymerase chain reaction (qPCR) and Western blot analyses.
In this two-generation family, the proband and his mother were diagnosed with unilateral microtia. Unilateral microtia and ipsilateral accessory ear were observed in one of the twins, who were sisters of the proband. The father and the other twin showed no abnormal clinical features. A heterozygous mutation of a C to T in the CYP26A1 gene, which leads to truncation of the CYP26A1 protein, was identified in this family. The nonsense mutation cosegregated with patients and was absent in normal members of the family. The prediction software indicated that it was a possibly pathogenic mutation. The structure of the protein varied significantly between the WT and mutant proteins. Functional analysis showed that this mutation caused a significant decrease in both the mRNA and protein levels.
Our findings suggest that this mutation of CYP26A1 may be a pathogenic factor leading to the phenotypes of microtia and accessory ear in this family. Further studies are needed to prove the function of this mutation and to explore the possible mechanism by which this variant is involved in the occurrence of microtia.
小耳畸形是一种先天性畸形，其特征为耳廓小、形态异常，伴或不伴外耳道闭锁或狭窄。本研究调查了一个 CYP26A1 基因（被认为对头面部发育很重要）的突变，该基因在一个小耳畸形家系中发生突变。
对先证者及其家系成员进行全外显子组测序（WES），以鉴定疾病相关变异。使用几种生物信息学工具分析改变的蛋白质的计算预测。将野生型（WT）和突变型 CYP26A1 cDNA 转染入人胚肾细胞，通过定量聚合酶链反应（qPCR）和 Western blot 分析比较 mRNA 和蛋白水平。
在这个两代人的家系中，先证者及其母亲被诊断为单侧小耳畸形。先证者的一个双胞胎姐妹患有单侧小耳畸形和同侧副耳，这对双胞胎的父亲和另一个双胞胎则无异常的临床特征。在 CYP26A1 基因中发现了一个杂合的 C 到 T 突变，导致 CYP26A1 蛋白的截断。这个无义突变与患者共分离，在家族中的正常成员中不存在。预测软件表明这是一个可能的致病性突变。WT 和突变蛋白之间的结构差异很大。功能分析表明，这种突变导致 mRNA 和蛋白水平均显著降低。
我们的研究结果表明，CYP26A1 的这种突变可能是导致该家系小耳畸形和副耳表型的致病因素。需要进一步研究来证明该突变的功能，并探讨该变异参与小耳畸形发生的可能机制。
