The Relationship Between Gene Region Polymorphisms And Congenital Heart Disease

Congenital heart disease (CHD) is the most frequent form of major birth defects in newborns with an incidence of about 19 to 75 per 1,000 live births, depending on the type and severity of the defects that are included. A statistical report from World Health Organization (WHO) shows that there are about 1.5 million children born with CHD each year. In China the number is about 150,000 per year and grows rapidly, thereby making CHD as the leading cause of infant mortality.Despite many advances in our understanding of cardiac development, the fundamental etiology for the majority of CHD cases remains unknown. It is generally understood that both genetic and environmental factors contribute to the highly complex etiology of CHD, by disrupting highly regulated embryonic developmental processes.The aim of this thesis was to seek the molecular mechanism of CHD by studying the association between miRNA gene polymorphisms and CHD (Part I) and that between Objective: Recent evidence indicates that small noncoding RNA molecules, called microRNAs (miRNAs), have emerged as a central regulator of many cardiogenic processes. Mutation, misexpression, and altered mature miRNA processing are implicated in CHD development. The aim of this study was to find the association between miRNA gene polymorphisms and CHD.Methods: We conducted a systematic survey of common miRNA single nucleotide polymorphisms (SNPs) and evaluated the association between 4 these SNPs and CHD. A three-stage case-control study of CHD in Chinese was used to test our hypothesis by genotyping miR-196a2 rs11614913 and three other pre-miRNA SNPs (miRNA-146a rs2910164, miRNA-149 rs2292832, and miRNA-499 rs3746444) in 1,324 CHD cases and 1,783 non-CHD controls. To further characterize the functional relevance of the miR-196a2 rs11614913 SNP, we conducted a correlation analysis between rs11614913 genotypes and the expression of mature miR-196a in the 29 CHD cardiac tissue specimens and generated HOXB8 3'UTR luciferase reporter plasmids that were cotransfected with miR-196a2 expression plasmids (rs11614913 C or T allele) in CHO and 293T cell lines to evaluate the influence of rs11614913 variants on the binding of target mRNA.Results: We found that miR-196a2 rs11614913 CC was associated with a significantly increased risk of CHD in all three stages combined (P=6.81×10-6). In a genotype-phenotype correlation analysis using 29 cardiac tissue samples of CHD, rs11614913 CC was associated with significantly increased mature miR-196a expression (P=0.001). In vitro binding assays further revealed that the rs11614913 Objective: Accumulative evidence has suggested that folate deficiency and hyperhomocysteinemia are associated with CHD risk. Inherited polymorphisms in key folate metabolic pathway genes, methylenetetrahydrofolate reductase (MTHFR) and methylenetetrahydrofolate dehydrogenase (MTHFD) may influence the efficiency of folate metabolism and change plasma level of homocysteine. The aim of this study was to investigate whether genetic variants in MTHFR and MTHFD genes are associated with CHD development.Methods: We conducted a two-stage case-control study of CHD in Chinese population by genotyping MTHFR 1793G>A (rs2274976) and other four variants (MTHFR 677C>T (rs1801133), 1298A>C (rs1801131), and MTHFD 1958G>A (rs2236225), 401C>T (rs1950902)) in 1,033 CHD cases and 1,067 non-CHD controls. Results: The variant genotypes of MTHFR 1793GA/AA were associated with a significantly decreased risk of CHD in two stages combined (P=0.0004) and the effect was especially on isolated perimembranous ventricular septal defect patients (P=0.0003), when compared with wild homozygote 1793GG.Conclusion: This study provided evidence that MTHFR 1793G>A might play a role in prediction of CHD susceptibility and contribute to CHD etiology.