Abstract:
Somatic cell nuclear transfer or cloning has been developed and successfully
used to produce cloned animals in many mammalian species. However, the knowledge
of somatic cell cloning in swamp buffalo has been extremely rare. The objective of
the present study was to establish an effective somatic cell cloning protocol for this
species. Buffalo and bovine oocytes obtained from abattoir ovaries were matured in
vitro and used for parthenogenetic activation, in vitro fertilization and nuclear transfer
experiments.
The results showed that calcium ionophore or ethanol used in combination
with 6-dimethylaminopurine effectively induces buffalo oocyte activation and
parthenogenetic development. The cleavage, blastocyst rate, and total number of cells
did not significantly differ in the four cell groups used: cumulus cells, fetal, calf and
adult fibroblast cells. Buffalo fetal fibroblasts can be successfully synchronized in the
quiescent G0/G1 phase of the cell cycle by serum starvation or roscovitine treatment
and in G1/S phase by aphidicolin treatment. The rates of blastocyst development of
embryos reconstructed with quiescent G0/G1 cells synchronized by serum starvation
were improved as compared to those derived from roscovitine and aphidicolin
treatments. The nuclear remodeling event of cloned embryos derived from serum
starved cells can occur in enucleated oocyte, mitotic division and can reach more
advanced stages faster than serum fed cells. Telomerase activity detection indicates the
successful reprogramming of telomerase activity in cloned embryos follow a similar
pattern as in embryos derived from in vitro fertilization and parthenogenetic
activation. The interspecies cloning experiments showed that the cytoplasm of
enucleated bovine oocyte has the ability to support the mitotic division of buffalo
somatic nuclei up to the blastocyst stage, and buffalo fetal fibroblasts can support the
in vitro development of interspecies cloned embryos after transfer to enucleated
bovine oocytes better than that of cumulus and oviductal cells.
These findings indicate that an effective somatic cell cloning protocol in
swamp buffalo was established in the present study and buffalo somatic cell nuclei can
be reprogrammed in enucleated bovine oocytes, resulting in the production of
interspecies cloned blastocysts.