Combined activation treatments of recipient cytoplasts prior to nuclear transfer improves development of cloned embryos

Abstract

The ibex (Capra ibex) is currently listed as a priority protected animal by the Chinese government. Due to the limited availability of ibex oocytes, the objective of this study was to explore the feasibility of using domestic goat (Capra hircus) cytoplasts to reprogram nuclei from ibex donor fibroblasts in interspecies nuclear transfer (iSCNT). An effort was thus made to produce ibex embryos via iSCNT. The trial was performed using three treatment groups. The embryo cleavage rates on day 3 of in vitro culture and the blastocyst development rates on day 7 were recorded. In Treatment A, the female ibex fibroblasts were used as donor cells and of the fused cell-cytoplast couplets, 68% cleaved and 11% reached the blastocyst stage. In Treatment B, domestic adult dairy doe fibroblasts were used as donor cells and as comparison of homologous nuclear transfer (NT). Of fused cell-cytoplast couplets, 76% cleaved and 31% reached the blastocyst stage. In Treatment C, the development of parthenogenetic goat oocytes was used as the control and 90% of the embryos cleaved and 43% reached the blastocyst stage. No significant difference was found between treatment groups A and B in embryo cleavage rate, but a significant difference (P < 0.01) was recorded between treatment groups A and B in the blastocyst production rate. There was a significant difference (P < 0.01) between Treatment C and Treatment A/B in embryo cleavage rate and blastocyst production rate. The results indicated that although both cleavage rate (68%) and blastocyst yield (11%) of iSCNT embryos derived from female ibex fibroblasts (Treatment A) were lower than those of nuclear transfer embryos (Treatment B) and parthenogenetic development embryos (Treatment C). The domestic goat (C. hircus) cytoplasts supported the mitotic cleavage of ibex karyoplasts and were capable of reprogramming the nucleus to achieve a blastocyst stage embryo in exotic Capra which has the potential of alleviating species on the endangered list.