02452naa a2200253 a 450000100080000000500110000800800410001902400310006010000200009124501200011126000090023152017140024065300190195465300150197365300140198870000210200270000170202370000210204070000220206170000160208370000170209970000180211677300640213410481562023-03-08       2007    bl uuuu     u00u1 u    #d7 a10.1089/clo.2006.00822DOI1 aFERREIRA, C. R.  aThe kinetics of donor cell mtDNA in embryonic and somatic donor cell-derived bovine embryos.h[electronic resource]  c2007  aThe mechanisms controlling the outcome of donor cell-derived mitochondrial DNA (mtDNA) in cloned animals remain largely unknown. This research was designed to investigate the kinetics of somatic and embryonic mtDNA in reconstructed bovine embryos during preimplantation development, as well as in cloned animals. The experiment involved two different procedures of embryo reconstruction and their evaluation at five distinct phases of embryo development to measure the proportion of donor cell mtDNA (Bos indicus), as well as the segregation of this mtDNA during cleavage. The ratio of donor cell (B. indicus) to host oocyte (B. taurus) mtDNA (heteroplasmy) from blastomere(NT-B) and fibroblast(NT-F) reconstructed embryos was estimated using an allele-specific PCR with fluorochrome-stained specific primers in each sampled blastomere, in whole blastocysts, and in the tissues of a fibroblast derived newborn clone. NT-B zygotes and blastocysts show similar levels of heteroplasmy (11.0% and 14.0%, respectively), despite a significant decrease at the 916 cell stage (5.8%; p &lt 0.05). Heteroplasmy levels in NT-F reconstructed zygotes, however, increased from an initial low level (4.7%), to 12.9% (p &lt 0.05) at the 9?16 cell stage. The NT-F blastocysts contained low levels of heteroplasmy (2.2%) and no somatic-derived mtDNA was detected in the gametes or the tissues of the newborn calf cloned. These results suggest that, in contrast to the mtDNA of blastomeres, that of somatic cells either undergoes replication or escapes degradation during cleavage, although it is degraded later after the blastocyst stage or lost during somatic development, as revealed by the lack of donor cell mtDNA at birth.  aBovine embryos  aCell mtDNA  aEmbryonic1 aMEIRELLES, F. V.1 aYAMAZAKI, W.1 aCHIARATTI, M. R.1 aNICIURA, S. C. M.1 aPERECIN, F.1 aSMITH, L. C.1 aGARCIA, J. M.  tCloning and Stem Cells.gv. 9, n. 4, p. 618-629, dec. 2007.