Tóm tắt
To preserve the female genetics of an endangered breed of cattle, adapted to
sub-Antarctic con-ditions, adult somatic cell nuclear transfer was used to
clone the last surviving Enderby Island cow from mural granulosa cells.
Embryos reconstructed with metaphase II cytoplasts and quiescent cells were
either activated and fused simultaneously (AFS) at 24 or 30 hours post
maturation (hpm) or alternatively, fused 4–6 h before activation at
26–30 hpm (FBA). A significantly higher proportion of fused embryos
developed in vitro to grade 1–3 blastocysts on Day
7 with FBA (39.82.8%) compared to AFS with activation either at 24 hpm
(10.63.9%, P<0.01) or at 30 hpm (18.64.1%, P<0.01).
Following the transfer of 74 embryos from the FBA treatment over two
experiments, survival rates on Days 30, 55, 85, 150 and 190 of pregnancy were
38%, 30%, 23%, 16% and 15%, respectively.
Of 22 embryos transferred in the first experiment, two calves were born alive
with one calf surviving. DNA analyses confirmed that the calves were
genetically identical to the Enderby Island cow. Additional pregnancies are
currently ongoing. These data show that embryo development is increased by
prolonged exposure of quiescent somatic cell nuclei to oocyte cytoplasm before
artificial activation, possibly facilitating nuclear reprogramming. The
successful demonstration of somatic cell nuclear transfer in animal
conservation extends the applications of the technology beyond the main
agri-cultural and biomedical interests.
