Resequencing the whole MYH7 gene (including the intronic, promoter, and 3´ UTR sequences) in hypertrophic cardiomyopathy

Abstract

MYH7 mutations are found in approximately 20% of hypertrophic cardiomyopathy (HCM) patients. Currently, mutational analysis is based on the sequencing of the coding exons and a few exon-flanking intronic nucleotides resulting in omission of single exon deletions and mutations in internal intronic, promoter, and 3´UTR regions. We amplified and sequenced large MYH7 fragments in 60 HCM patients without a previously identified sarcomere mutation. Lack of aberrant PCR-fragments excluded single exon deletions from the patients. Instead, we identified several new rare intronic variants. An intron 26 single nucleotide insertion (-5 insC) was predicted to affect pre-mRNA splicing, but allele frequencies did not differ between patients and controls (n=150). We found several rare promoter variants in the patients compared to the controls, some of which were in binding sites for transcription factors, and could thus affect gene expression. Only one rare 3´UTR variant (c.*29T>C) found in the patients was absent among the controls. This nucleotide change would not affect the binding of known micro-RNAs. Therefore, MYH7 mutations outside the coding exon sequences would be rarely found among HCM patients. However, changes in the promoter region could be linked to the risk of developing HCM. Further research to define the functional effect of these variants on gene expression should be necessary to confirm the role of the MYH7 promoter on cardiac hypertrophy.