Transcription factor A mitochondria (TFAM) is an important activator of mitochondrial DNA transcription and replication. Studies in mice have shown that TFAM is required to regulate the mitochondrial genome copy number and is important for embryonic development. TFAM has been associated with mitochondrial disorder which includes ocular myopathy and muscular wasting in humans. Kearns-Sayre syndrome was shown in mouse model when expression of the gene was eliminated by targeted disruption in heart and muscle cells.