Association between COL3A1 collagen gene exon 31 polymorphism and risk of floppy mitral valve/mitral valve prolapse

Background: Collagen structure is a key element in mitral valves. Collagen defects were proposed as the primary events causing floppy mitral valves (FMV). The role of collagen genetic variant in floppy mitral valve/mitral valve prolapse (FMV/MVP) has not been well studied. The purpose of this study is to investigate the possible relationship between the collagen gene polymorphisms and risk of FMV/MVP among the Chinese population in Taiwan. Methods: We studied 100 patients with FMV/MVP diagnosed by echocardiography and 243 age- and sex-matched normal control subjects. The polymorphisms of exon 31 and exon 52 of the collagen type III-α1 gene (COL3A1) were identified by polymerase chain reaction (PCR)-based restriction analysis. Results: There was a significant difference in either the genotype distribution (P<0.0001) or allelic frequencies (P<0.0001) between FMV/MVP cases and controls for COL3A1 exon 31 polymorphism. An odds ratio for risk of FMV/MVP associated with COL3A1 exon 31 GG genotype was 7.42 (95% confidence interval 4.40-12.52). An odds ratio for risk of FMV/MVP associated with COL3A1 exon 31 G allele was 2.28 (95% confidence interval 1.57-3.29). There was no significant difference in the distribution of COL3A1 exon 52 genotypes (P=0.31) and allelic frequencies (P=0.32) between FMV/MVP cases and controls. Further categorization of the FMV/MVP patients into mild and severe subgroups revealed no statistical difference from the controls for exon 31 or exon 52 polymorphism. Conclusions: This study shows that patients with FMV/MVP have higher frequency of COL3A1 exon 31 GG genotype that supports a role of the COL3A1 exon 31 polymorphism in determining the risk of FMV/MVP among the Chinese population in Taiwan.