Complete loss of expression of the ANT1 gene causing cardiomyopathy and myopathy

Background The ANT1 gene, encoding ADP/ATP translocase 1, was investigated in an adult patient with an autosomal recessive mitochondrial disorder characterised by congenital cataracts, hypertrophic cardiomyopathy, myopathy and lactic acidosis. Methods and results ANT1 sequencing showed that the patient was homozygous for a new nucleotide variation, c.111+1G -> A, abolishing the invariant GT splice donor site of intron 1. The ANT1 transcript was undetectable in both muscle and skin fibroblasts. A markedly abnormal metabolic profile was found, and skeletal muscle showed a dramatic proliferation of abnormal mitochondria, increased mitochondrial mass, and multiple mitochondrial DNA deletions. No compensating increase in the transcript level of the ANT3 gene, which encodes the human ubiquitous isoform of the ADP/ATP translocase, was observed. The patient's heterozygous mother had normal clinical, biochemical and pathological features. Conclusions Complete loss of expression of the ANT1 gene causes a clinical syndrome mainly characterised by cardiomyopathy and myopathy. This report expands the clinical spectrum of ANT1-related human diseases, and emphasises the crucial role of the mitochondrial ADP/ATP carriers in muscle function and pathophysiology of human myopathies.