Abnormal H-Tfam in a patient harboring a single mtDNA deletion

We report on a patient suffering from a progressive mitochondrial disorder characterized by ocular myopathy, exercise intolerance, and muscle wasting. Morphological examination of muscle biopsy showed increased variability in fiber size and scattered ragged-red fibers. Analysis of muscle mitochondrial DNA by Southern blot and PCR revealed a heteroplasmic single deletion of 4100 base pairs, located between nucleotide positions 8300 and 12,400. Western blot analysis showed high levels of the human mitochondrial transcription factor A (Tfam). Interestingly, we also detected an additional Tfam product, of approximately 22 kDa. This is the first case in which a qualitatively abnormal Tfam has been found to be associated with a mitochondrial disorder in humans.