title: Mitogenomes of polar bodies and corresponding oocytes.
abstract: The objective of the present study was to develop an approach that could assess the chromosomal status and the mitochondrial DNA (mtDNA) content of oocytes and their corresponding polar bodies (PBs) with the goal of obtaining a comparative picture of the segregation process both for nuclear and mtDNA. After Whole Genome Amplification (WGA), sequencing of the whole mitochondrial genome was attempted to analyze the segregation of mutant and wild-type mtDNA during human meiosis. Three triads, composed of oocyte and corresponding PBs, were analyzed and their chromosome status was successfully assessed. The complete mitochondrial genome (mitogenome) was almost entirely sequenced in the oocytes (95.99% compared to 98.43% in blood), while the percentage of sequences obtained in the corresponding PB1 and PB2 was lower (69.70% and 69.04% respectively). The comparison with the mtDNA sequence in blood revealed no changes in the D-loop region for any of the cells of each triad. In the coding region of blood mtDNA and oocyte mtDNA sequences showed full correspondence, whereas all PBs had at least one change with respect to the blood-oocyte pairs. In all, 9 changes were found, either in PB1 or PB2: 4 in MT-ND5, 2 in MT-RNR2, and 1 each in MT-ATP8, MT-ND4, MT-CYTB. The full concordance between oocyte and blood in the 3 triads, and the relegation of changes to PBs, revealed the unexpected coexistence of different variants, giving a refined estimation of mitochondrial heteroplasmy. Should these findings be confirmed by additional data, an active mechanism could be postulated in the oocyte to preserve a condition of 'normality'.
authors.forename: Luca
authors.initials: L
authors.lastname: Gianaroli
authors.affiliation: SISMER Reproductive Medicine Unit, Bologna, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Gianoarli
authors.affiliation: Alma Mater Studiorum, University of Bologna, Bologna, Italy.
authors.forename: Donata
authors.initials: D
authors.lastname: Luiselli
authors.affiliation: SISMER Reproductive Medicine Unit, Bologna, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Crivello
authors.affiliation: Alma Mater Studiorum, University of Bologna, Bologna, Italy.
authors.forename: Martin
authors.initials: M
authors.lastname: Lang
authors.affiliation: SISMER Reproductive Medicine Unit, Bologna, Italy.
authors.forename: Anna Pia
authors.initials: AP
authors.lastname: Ferraretti
authors.affiliation: Alma Mater Studiorum, University of Bologna, Bologna, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: De Fanti
authors.affiliation: SISMER Reproductive Medicine Unit, Bologna, Italy.
authors.forename: M Cristina
authors.initials: MC
authors.lastname: Magli
authors.affiliation: Alma Mater Studiorum, University of Bologna, Bologna, Italy; European School of Genetic Medicine, Bologna, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Romeo
mesh_terms: D001483:Base Sequence; D020090:Chromosome Segregation / Q000235:genetics; D002875:Chromosomes / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D014644:Genetic Variation; D054629:Genome, Mitochondrial / Q000235:genetics*; D006801:Humans; D008540:Meiosis / Q000235:genetics; D008928:Mitochondria / Q000235:genetics; D008969:Molecular Sequence Data; D009865:Oocytes / Q000166:cytology*; D059705:Polar Bodies / Q000166:cytology*; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial