REARRANGED MITOCHONDRIAL GENOMES ARE PRESENT IN HUMAN OOCYTES

Using quantitative PCR, we have determined that a human oocyte contain s similar to 100,000 mitochondrial genomes (mtDNAs). We have also foun d that some oocytes harbor measurable levels (up to 0.1%) of the so-ca lled common deletion, an mtDNA molecule containing a 4,977-bp rearrang ement that is present in high amounts in many patients with ''sporadic '' Kearns-Sayre syndrome (KSS) and progressive external ophthalmoplegi a (PEO). This is the first demonstration that rearranged mtDNAs are pr esent in human oocytes, and it provides experimental support for the s upposition that pathogenic deletions associated with the ontogeny of s poradic KSS and PEO can be transmitted in the female germ line, from m other to child. The relevance of these findings to the accumulation of extremely low levels of deleted mtDNAs in both somatic and germ-line tissues during normal human aging is also discussed.