Functional Study Of Candidate Genes For Congenital Heart Defects On Chromosome 8p

Background:The heart is the first organ to have function during embryonic development,any disruption will lead to the occurrence of congenital heart disease（CHD）.The prevalence of CHD at birth is estimated to be 80 per 10000 live births,occupying 1/3 of all the major birth defects,and it is the leading cause of neonatal morbidity and mortality.The postoperative effect of CHD is not good,which seriously threat the newborns health ^1,2.The outflow tract（OFT）defects,such as Tetralogy of Fallot（TOF）,double outlet right ventricle（DORV）,transposition of the great arteries（TGA）,pulmonary atresia（PA）,and persistent truncus arteriosus（PTA）,make up a large percentage of 30%of human CHD.The etiology of CHD is complex,and it is caused predominantly by genetic factors,including single-gene mutations and chromosomal aberrations.However,the genetic mechanism underlying CHD is incompletely understood,and much attention need to be paid to the association between the disease and certain chromosomal aberrations,as well as exploration of more CHD susceptible genes.This study may provide evidences for early diagnosis,genetic counseling for CHD.Objective:To study the function of SOX7,which maps to distal chromosome 8p,in OFT development.Mutation screen and functional analysis of SOX7 in patients with cardiac OFT defects.Identification of critical region and candidate genes for CHD on chromosome 8p,and analysis of the pathogenic mechanisms.Results:1.Overexpression of SOX7 repress EMT process in cardiac OFT;2.SOX7active the expression of downstream target gene CDH5;3.Effects of SOX7 mutations found in cardiac OFT defects individuals on protein expression,transcriptional regulation on target gene CDH5,and Wnt/β-catenin signal pathway;4.Karyotype and Cyto Scan HD array analysis showed the proband had an 18.5-Mb deletion at 8p11.23–p22 that include the cardiac-associated loci NKX2-6 and NRG1;5.Further mutation screening of these two candidate genes in 143 atrial septal defect patients,and two heterozygous mutations NKX2-6（c.1A?>?T）and NRG1（c.1652G?>?A）were identified.The c.1A?>?T NKX2-6 generated a protein truncated by 45 amino acids with a decreased level of m RNA expression,whereas the NRG1 mutation had no significant effect on protein functions.Conclusion:1.Our study firstly investigated the role of SOX7 on cardiac OFT development,and screen SOX7 mutation in patients with cardiac OFT defects and analysis pathogenic mechanism by molecular biology technology;2.We describe a proximal 8p deletion in child and summarize the clinical and molecular cytogenetics findings for this patient,as well as review those for previously reported patients,and conclude that proximal 8p21–8p12 is another critical region for CHD.CHD associated with proximal 8p deletion is likely due to haploinsufficiency of the cardiac transcription factor NKX2.6.In the meantime,our study is the first report of NKX2.6 mutation in ASD patient,expending our understanding of the mechanism of ASD.