Proliferation of donor mitochondrial DNA in nuclear transfer calves (Bos taurus) derived from cumulus cells.
In embryos derived by nuclear-transfer (NT), fusion of donor cell and recipient oocyte caused mitochondrial heteroplasmy. Previous studies from other laboratories have reported either elimination or maintenance of donor-derived mitochondrial DNA (mtDNA) from somatic cells in cloned animals. Here we examined the distribution of donor mtDNA in NT embryos and calves derived from somatic cells. Donor mitochondria were clearly observed by fluorescence labeling in the cytoplasm of NT embryos immediately after fusion; however, fluorescence diminished to undetectable levels at 24 hr after nuclear transfer. By PCR-mediated single-strand conformation polymorphism (PCR-SSCP) analysis, donor mtDNAs were not detected in the NT embryos immediately after fusion (less than 3-4%). In contrast, three of nine NT calves exhibited heteroplasmy with donor cell mtDNA populations ranging from 6 to 40%. These results provide the first evidence of a significant replicative advantage of donor mtDNAs to recipient mtDNAs during the course of embryogenesis in NT calves from somatic cells.
Takeda
Kumiko
K
Department of Animal Breeding and Reproduction, National Institute of Livestock and Grassland Science, National Agricultural Research Organization, Ikenodai 2, Tsukuba, Ibaraki 305-0901, Japan. kumiko@affrc.go.jp
Akagi
Satoshi
S
Kaneyama
Kanako
K
Kojima
Toshiyuki
T
Takahashi
Seiya
S
Imai
Hiroshi
H
Yamanaka
Mariko
M
Onishi
Akira
A
Hanada
Hirofumi
H
D000818:Animals; D002417:Cattle; D019976:Cloning, Organism; D004272:DNA, Mitochondrial / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000378:metabolism*; D005838:Genotype
D004272:DNA, Mitochondrial