Mitochondial DNA deletions in Iranian hypertrophic cardiomyopathy patients

Background: Hypertrophic cardiomyopathy is a genetic disorder with autosomal dominant inheritance. The disorder has been estimated to occur in 0.05%-0.2% of population. Recently mitochondrial DNA mutations have been associated with cardiomyopathies. Mitochondria are the major site of energy production in the cell. Thus it is reasonable to assume that energy dependant tissues such as heart, brain, skeletal muscle and endocrine system are affected by mitochondrial dysfunction. Many mitochondrial diseases arise form defects of the mitochondrial respiratory chain. Since mtDNA is predominantly maternally inherited, mitochondrial disorders have maternal inheritance pattern. The mtDNA mutation rate is much higher than nuclear DNA due to lack of a repair mechanism and also having no intron. Recent studies have reported maternally inherited, non-x linked HCMs are associated with defects in mitochondrial oxidative metabolism. Methods: In this study we screened 52 Iranian hypertrophic cardiomyopathic patients for mitochondrial DNA deletions. Results: Mitochondrial DNA deletions were detected by PCR using 6 paired primers. Five different deletions were found in 29 patients (55.8%). Eighteen patients (34.4%) showed 8.5 kb deletion. Twelve (23%) patients had 9 kb deletion. Seven patients (13.4%) had a 7.3 kb deletion. Eight patients (15.5%) had 4977 bp common deletion between nt8161-nt13640, and 11 patients had 7.4 kb deletion. Multiple deletions have been found in 11 patients (21.1%). Conclusion: Mitochondrial DNA deletions may occur as a result of aging; on the other hand mt deletions may affect myocardium and lead to secondary hypertrophy. However, the question regarding primary or secondary role of mt deletions in hyperthrophic cardiomyopathy remains unanswered.