Published online by Cambridge University Press: 05 April 2012
Interspecies somatic cell nuclear transfer (ISCNT) has been proposed as a technique to produce cloned offspring of endangered species as well as to investigate nucleus–cytoplasm interactions in mammalian embryo. However, it is still not known which embryo culture medium is optimal for ISCNT embryos for the nuclear donor or the oocyte recipient. We assessed the effects of the culture medium on the developmental competence of the ISCNT embryos by introducing cynomolgus monkey (Macaca fascicularis) fibroblast nuclei into enucleated rabbit (Oryctolagus cuniculus) oocytes (monkey–rabbit embryo). The monkey–rabbit ISCNT embryos that were cultured in mCMRL-1066 developed to the blastocyst stage, although all monkey–rabbit ISCNT embryos cultured in M199 were arrested by the 4-cell stage. When monkey–rabbit ISCNT and rabbit–rabbit somatic cell nuclear transfer (SCNT) embryos were cultured in mCMRL-1066, the blastocyst cell numbers of the monkey–rabbit ISCNT embryos corresponded to the cell numbers of the control rabbit–rabbit SCNT embryos, which were produced from a rabbit fibroblast nucleus and an enucleated rabbit oocyte. In addition, the presence of mitochondria, which were introduced with monkey fibroblasts into rabbit recipient cytoplasm, was confirmed up to the blastocyst stage by polymerase chain reaction (PCR). This study demonstrated that: (1) rabbit oocytes can reprogramme cynomolgus monkey somatic cell nuclei, and support preimplantation development; (2) monkey–rabbit ISCNT embryos developed well in monkey culture medium at early embryonic developmental stages; (3) the cell number of monkey–rabbit ISCNT embryos is similar to that of rabbit–rabbit SCNT embryos; and (4) the mitochondrial fate of monkey–rabbit ISCNT embryos is heteroplasmic from the time just after injection to the blastocyst stage that has roots in both rabbit oocytes and monkey fibroblasts.