孤独症谱系障碍合并先天性心脏病患儿1例的NSD1基因变异分析

Analysis of NSD1 gene variant in a child with autism spectrum disorder in conjunct with congenital heart disease

目的探讨1例孤独症谱系障碍(ASD)合并先天性心脏病(CHD)患儿的临床特征与遗传学病因。方法选取2021年4月13日于成都市第三人民医院就诊的1例ASD合并CHD患儿为研究对象。收集患儿临床资料,采集患儿及其父母外周静脉血样,应用全外显子组测序(WES)对患儿进行基因检测,使用GTX遗传分析系统对WES数据进行分析,筛选出ASD候选致病基因。进一步采用Sanger测序进行家系验证,并对候选变异进行生物信息学分析。利用实时荧光定量PCR(qPCR)技术,检测本研究患儿与3例正常同龄儿童和5例其他ASD患儿NSD1基因mRNA相对表达量的差异。结果患儿为男性,8岁,主要临床表现为ASD、智力低下及CHD。WES数据经GTX遗传分析系统分析,NSD1被筛选为该本研究患儿ASD候选致病基因,其NSD1基因存在c.3385+2T>C杂合变异,Sanger测序结果显示,患儿父母均未携带该变异,提示该变异为新发变异。生物信息学分析:NSD1基因c.3385+2T>C变异在ESP、1000 Genomes及ExAC等数据库中均未见收载;采取Mutation Taster在线软件对该变异有害性分析结果显示,提示为可能有害变异;根据美国医学遗传学与基因组学学会(ACMG)指南,该变异被评级为致病性变异。qPCR检测结果显示,与3例正常同龄儿童相比,本研究患儿和其他5例确诊ASD患儿的NSD1基因mRNA相对表达量均显著降低,并且差异有统计学意义(P<0.001)。结论NSD1基因c.3385+2T>C变异可导致其mRNA表达水平显著降低,与ASD具有一定关联,可能是本研究ASD患儿的遗传学病因,进一步拓展了NSD1基因变异谱。

Objective To explore the clinical characteristics and genetic basis of a child with autism spectrum disorder(ASD)in conjunct with congenital heart disease(CHD).Methods A child who was hospitalized at the Third People′s Hospital of Chengdu on April 13,2021 was selected as the study subject.Clinical data of the child were collected.Peripheral blood samples of the child and his parents were collected and subjected to whole exome sequencing(WES).A GTX genetic analysis system was used to analyze the WES data and screen candidate variants for ASD.Candidate variant was verified by Sanger sequencing and bioinformatics analysis.Real-time fluorescent quantitative PCR(qPCR)was carried out to compare the expression of mRNA of the NSD1 gene between this child and 3 healthy controls and 5 other children with ASD.Results The patient,an 8-year-old male,has manifested with ASD,mental retardation and CHD.WES analysis revealed that he has harbored a heterozygous c.3385+2T>C variant in the NSD1 gene,which may affect the function of its protein product.Sanger sequencing showed that neither of his parent has carried the same variant.By bioinformatic analysis,the variant has not been recorded in the ESP,1000 Genomes and ExAC databases.Analysis with Mutation Taster online software indicated it to be disease causing.Based on the guidelines from the American College of Medical Genetics and Genomics(ACMG),the variant was predicted to be pathogenic.By qPCR analysis,the expression level of mRNA of the NSD1 gene in this child and 5 other children with ASD was significantly lower than that of the healthy controls(P<0.001).Conclusion The c.3385+2T>C variant of the NSD1 gene can significantly reduce its expression,which may predispose to ASD.Above finding has enriched the mutational spectrum the NSD1 gene.