Mitochondrial DNA deletion in human oocytes and embryos (original) (raw)

Mitochondrial DNA rearrangements in human oocytes and embryos

Molecular Human Reproduction, 1999

rearrangements, including more than 150 deletions and insertions, accumulate with age and are responsible for certain neuromuscular diseases. Human oocytes, arrested for up to 50 years, may express certain mtDNA rearrangements possibly affecting function. Investigations have previously shown a single mtDNA rearrangement (dmtDNA 4977 ) in human oocytes. Sequencing of other rearrangements and their correlation with maternal age have not been performed in human oocytes or embryos. Here we use a nested PCR strategy of long followed by short polymerase chain reaction (PCR) that amplifies two-thirds of the mitochondrial genome. mtDNA rearrangements were detected in 50.5% of the oocytes (n ⍧ 295) and 32.5% of the embryos (n ⍧ 197). This represents a significant difference in the percentage of mtDNA rearrangements between oocytes and embryos (P < 0.0001). Twenty-three novel mtDNA rearrangements with deletions, insertions and duplications were found. There was no significant age-related increase in the percentage of human oocytes or embryos that contained mtDNA rearrangements. Significant reductions in the number of oocytes containing mtDNA rearrangements occurred as oocyte development progressed from germinal vesicle to the mature metaphase II oocyte (P < 0.05). These findings are discussed as they relate to mitochondria, mtDNA, and ATP production in human oocytes and embryos.

Identical Mitochondrial DNA Deletion in a Woman with Ocular Myopathy and in Her Son with Pearson Syndrome

2002

Single deletions of mitochondrial DNA (mtDNA) are associated with three major clinical conditions: Kearns-Sayre syndrome, a multisystem disorder; Pearson syndrome (PS), a disorder of the hematopoietic system; and progressive external ophthalmoplegia (PEO), primarily affecting the ocular muscles. Typically, single mtDNA deletions are sporadic events, since the mothers, siblings, and offspring of affected individuals are unaffected. We studied a woman who presented with PEO, ptosis, and weakness of pharyngeal, facial, neck, and limb muscles. She had two unaffected children, but another of her children, an infant son, had sideroblastic anemia, was diagnosed with PS, and died at age 1 year. Morphological analysis of a muscle biopsy sample from the mother showed cytochrome c oxidase-negative ragged-red fibers-a typical pattern in patients with mtDNA deletions. Southern blot analysis using multiple restriction endonucleases and probed with multiple mtDNA fragments showed that both the mother and her infant son harbored an identical 5,355-bp single deletion in mtDNA, without flanking direct repeats. The deletion was the only abnormal species of mtDNA identified in both patients, and there was no evidence for duplications. We conclude that, although the vast majority of single large-scale deletions in mtDNA are sporadic, in rare cases, single deletions can be transmitted through the germline. Mitochondria, the main sources of cellular energy, are under the dual control of mtDNA and nuclear DNA. mtDNA, a small, 16.5-kb molecule, encodes 13 subunits of the respiratory-chain complexes, as well as 22 tRNAs and 2 ribosomal RNAs (Anderson et al. 1981). Largescale single deletions of mtDNA are associated with three major clinical conditions: Kearns-Sayre syndrome (KSS [MIM 530000]), progressive external ophthalmoplegia (PEO [MIM 258450]), and Pearson syndrome (PS [MIM 557000]). Virtually all patients with KSS harbor single mtDNA deletions that are detectable in muscle and other tissues by Southern blot analysis (Zeviani et al. 1988; Moraes et al. 1989). Approximately 50% of patients with PEO and ragged-red fibers have single mtDNA deletions

Developmental genetics of deleted mtDNA in mitochondrial oculomyopathy

Journal of the Neurological Sciences, 1997

Heteroplasmicpopulationsof mtDNA,consistingof normalmtDNAandmtDNAwith largedeletions,are foundin the skeletalmuscle and other tissues of certain patients with mitochondrialrespiratorychain deficiencies,particularly in those with the CPEO (chronic progressiveexternalophthalmoplegia) phenotype.To studythe developmental geneticsof this mitochondrialdisorder,the distributionof the deletedmtDNAin a wide rangeof tissuesof differentembryonicorigins(total 34 samplesfrom 27 tissuesobtainedat autopsy)was investigatedin a patientwiththe CPEOsyndrome.Threespeciesof partiallydeletedmtDNAwereobserved,with deletionsof 2.3 kb, 5.0 kb and 6.4 kb. Theirtissuedistributionsuggeststhat the mtDNAdeletionshaveoccurredveryearly duringembryonicdevelopment, prior to the differentiationeventsthat lead to the formationof the threeprimaryembryonicgerm layers, and that the partiallydeletedmtDNA specieswere segregatedduringdevelopmentmainlyto the skeletalmuscleand to tissuesof the central nervoussystem.0 1997Elsevier ScienceB.V. All rightsreserved.