Influence of Intergeneric/Interspecies Mitochondrial Injection; Parthenogenetic Development of Bovine Oocytes after Injection of Mitochondria Derived from Somatic Cells

Abstract

Abstract. Interspecies/intergeneric mitochondrial heteroplasmy can occur in interspecies/intergeneric hybrid embryos or following nuclear transfer. In the present study, intergeneric buffalo (Bubalus bubalis) mitochondria (WB-mt) or interspecies murine (Mus spretus) mitochondria (M-mt) were injected into bovine (Bos taurus) oocytes, and the subsequent embryonic development was characterized. Fibroblast mitochondria (WB-mt or M-mt) were microinjected into in vitro matured bovine oocytes followed by oocyte activation by a combination of electrical stimulation and 6-dimethylaminopurine treatment. After seven days of culture, embryo development was evaluated. The copy number of specific mtDNA populations (introduced and native mtDNA) from heteroplasmic oocytes was estimated using real-time PCR. The results illustrated that oocytes injected with either WB-mt or M-mt can develop to the blastocyst stage (20.6% and 19.6%). Cleavage division rates and development to the morula stage in oocytes injected with WB-mt were lower (76.2% and 45.9%, respectively) in comparison with uninjected oocytes (89.2% and 59.1%, respectively) (P<0.05). However, no differences were found in comparing M-mt injected oocytes and controls (P>0.05). An increase in bovine mtDNA copy number was observed at the expanded blastocyst stage of injected embryos (P<0.01), while the number of injected mtDNA was stable throughout development. This study demonstrates that interspecies/intergeneric mitochondrial injected bovine oocytes have the ability to develop to the blastocyst stage after parthenogenetic activation and that injected mtDNA was neither selectively destroyed nor enhanced through development. Moreover, injected intergeneric mitochondria had a demonstrated influence on bovine parthenogenetic development and mtDNA replication. Key words: Bovine oocyte, Mitochondria, Mouse, mtDNA, Water buffalo (J. Reprod. Dev. 58: [323][324][325][326][327][328][329] 2012) S omatic cell nuclear transfer (SCNT) offers the possibility of preserving endangered species, and SCNT has been applied to many mammalian species [1]. However, owing to the limited availability of oocytes from wild animals, the cloning of endangered species benefits from the use of recipient oocytes from a related domestic species. However, this methodology results in the production of nuclear-cytoplasmic hybrids [2,3]. Despite numerous attempts in a wide variety of species, the number of live births of cloned offspring is still limited in instances that combine genetic compartments of closely related species [4,5]. The generation of animals through interspecies/intergeneric SCNT (iSCNT) poses several problems including mitochondrial/genomic DNA incompatibility, embryonic genome activation of the donor nucleus by the recipient oocyte, and availability of suitable foster mothers for iSCNT embryos. The species-specific nature of mitochondrial biogenesis and function makes this modeling particularly significant for iSCNT.F1 hybrids and iSCNT live offspring obtained using river buffalo (Bubal...

Manipulating the Mitochondrial Genome To Enhance Cattle Embryo Development

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