Interspecies somatic cell nuclear transfer (iSCNT) is a promising method to clone endangered animals
from which oocytes are difficult to obtain. Monomeric red fluorescent protein 1 (mRFP1) is an excellent
selection marker for transgenically modified cloned embryos during somatic cell nuclear transfer (SCNT).
In this study, mRFP-expressing rhesus monkey cells or porcine cells were transferred into enucleated por-
cine oocytes to generate iSCNT and SCNT embryos, respectively. The development of these embryos was
studied
in vitro
. The percentage of embryos that underwent cleavage did not significantly differ between
iSCNT and SCNT embryos (
P
> 0.05; 71.53% vs. 80.30%). However, significantly fewer iSCNT embryos than
SCNT embryos reached the blastocyst stage (2.04% vs. 10.19%,
P
< 0.05). Valproic acid was used in an
attempt to increase the percentage of iSCNT embryos that developed to the blastocyst stage. However,
the percentages of embryos that underwent cleavage and reached the blastocyst stage were similar
between untreated iSCNT embryos and iSCNT embryos treated with 2 mM valproic acid for 24 h
(72.12% vs. 70.83% and 2.67% vs. 2.35%, respectively). These data suggest that porcine-rhesus monkey
interspecies embryos can be generated that efficiently express mRFP1. However, a significantly lower
proportion of iSCNT embryos than SCNT embryos reach the blastocyst stage. Valproic acid does not
increase the percentage of porcine-rhesus monkey iSCNT embryos that reach the blastocyst stage. The
mechanisms underling nuclear reprogramming and epigenetic modifications in iSCNT need to be inves-
tigated further.