Maternal inheritance of mitochondrial DNA

Abstract

Mammalian mitochondrial DNA (mtDNA) is thought to be strictly maternally inherited. 1,2 Sperm mitochondria disappear in early embryogenesis by selective destruction, inactivation, or simple dilution by the vast surplus of oocyte mitochondria. 3 Very small amounts of paternally inherited mtDNA have been detected by the polymerase chain reaction (PCR) in mice after several generations of interspecif-ic backcrosses. 4 Studies of such hybrids and of mouse oocytes microinjected with sperm support the hypothesis that sperm mitochondria are targeted for destruction by nuclear-encoded proteins. 5-7 We report the case of a 28-year-old man with mitochondrial myopathy due to a novel 2-bp mtDNA deletion in the ND2 gene (also known as MTND2), which encodes a sub-unit of the enzyme complex I of the mitochondrial respiratory chain. We determined that the mtDNA harboring the mutation was paternal in origin and accounted for 90 percent of the patient's muscle mtDNA.