Proteomic profiling of sudden cardiac death with acquired cardiac hypertrophy.

BACKGROUND: Cardiac hypertrophy, which develops in middle-aged and older individuals as a consequence of hypertension and obesity, is an established risk factor for sudden cardiac death (SCD). However, it is sometimes difficult to differentiate SCD with acquired cardiac hypertrophy (SCH) from compensated cardiac hypertrophy (CCH), at autopsy. We aimed to elucidate the proteomic alteration in SCH, which can be a guideline for future postmortem diagnosis. METHODS: Cardiac tissues were sampled at autopsy. SCH group consisted of ischemic heart failure, hypertensive heart failure, and aortic stenosis. CCH group included cases of non-cardiac death with cardiac hypertrophy. The control group comprised cases of non-cardiac death without cardiac hypertrophy. All patients were aged > 40 years, and hypertrophic cardiomyopathy was not included in this study. We performed histological examination and shotgun proteomic analysis, followed by quantitative polymerase chain reaction analysis. RESULTS: Significant obesity and myocardial hypertrophy, and mild myocardial fibrosis were comparable in SCH and CCH cases compared to control cases. The proteomic profile of SCH cases was distinguishable from those of CCH and control cases, and many sarcomere proteins were increased in SCH cases. Especially, the protein and mRNA levels of MYH7 and MYL3 were significantly increased in SCH cases. CONCLUSION: This is the first report of cardiac proteomic analysis in SCH and CCH cases. The stepwise upregulation of sarcomere proteins may increase the risk for SCD in acquired cardiac hypertrophy before cardiac fibrosis progresses significantly. These findings can possibly aid in the postmortem diagnosis of SCH in middle-aged and older individuals.

A Complete Absence of Missense Mutation in Myosin Regulatory and Essential Light Chain Genes of South Indian Hypertrophic and Dilated Cardiomyopathies.

BACKGROUND: Myosin is a hexameric contractile protein composed of 2 heavy chains associated with 4 light chains of 2 distinct classes - 2 regulatory light chains (MYL2) and 2 essential light chains (MYL3). The myosin light chains stabilize the long alpha helical neck of the myosin head and regulate the myosin ATPase activities. OBJECTIVES: Mutations in MYL2 and MYL3 are reported to be associated with cardiomyopathies. However, there is no study available on these genes in Indian cardiomyopathies, and therefore we planned to study them. METHOD: For the first time we sequenced MYL2 and MYL3 genes in a total of 248 clinically well-characterized cardiomyopathies consisting of 101 hypertrophic and 147 dilated cases along with 207 healthy controls from south India. RESULTS: Our study revealed a total of 10 variations - 7 in MYL2 and 3 in MYL3, of which 3 are novel variations observed exclusively in cases. However, the 15 causative missense mutations previously reported are totally absent in our study, which showed that the sequences of MYL2 and MYL3 are highly conserved in Indian cases/controls. CONCLUSIONS: MYL2 and MYL3 mutations are rare and the least cause of cardiomyopathies in Indians.

Molecular cloning and mRNA expression analysis of sheep MYL3 and MYL4 genes.

Using longissimus dorsi muscles of Dorper sheep as the experimental materials, the complete cDNAs of ovine MYL3 (Myosin light chain 3) and MYL4 (Myosin light chain 4) genes were cloned using RT-PCR, 5' RACE and 3' RACE. We obtained 925-bp and 869-bp full-length cDNAs and submitted their sequences to GenBank as accession numbers of KJ710703 and KJ768855, respectively. The cDNAs contained 600-bp and 582-bp open reading frames (ORFs) and encoded proteins comprising 199 and 193 amino acid residues, respectively. Neither protein was predicted to have a signal peptide, but both were predicted to have several N-glycosylation, O-glycosylation, and phosphorylation sites. The secondary structures of MYL3 and MYL4 were predicted to be 40.70% and 48.70% α- helical, respectively. Sequence alignment showed that the MYL3 and MYL4 proteins of Ovis aries both shared more than 91% amino acid sequence similarity with those of Mus musculus, Homo sapiens, Rattus norvegicus, Bos taurus, and Sus scrofa. The levels of MYL3 and MYL4 mRNA in various sheep tissues were determined using qRT-PCR. The results showed that both mRNAs were highly expressed in the heart. This study has established a foundation for further investigation of the ovine MYL3 and MYL4 genes.