57 Embryo development following interspecies nuclear transfer of African buffalo (Syncerus Caffer), bontebok (Damaliscus Dorcus Dorcus) and eland (Taurotragus Oryx) somatic cells into bovine cytoplasts

Abstract

Wildlife conservation requires traditional as well as innovative conservation strategies in order to preserve gene and species diversity. Interspecies nuclear transfer has the potential to conserve genes from critically endangered wildlife species where few or no oocytes are available from the endangered species, and where representative cell lines have been established for the wildlife population while numbers were still abundant. The purpose of this study was to investigate the developmental ability of embryos reconstructed with transfer of somatic cells from the African buffalo (Syncerus caffer), bontebok (Damaliscus dorcus dorcus) and eland (Taurotragus oryx) to enucleated domestic cattle (Bos taurus) oocytes. Skin tissue from the three wildlife species were collected by surgically removing approx. 1.0�_�1.0�cm ear skin notches from animals immobilized with a combination of etorphine hydrochloride (M99; South Africa) and azaperone (Stressnil, South Africa). The biopsies were placed into physiological saline and transported to the laboratory at 4�C within 2�h, cleaned with chlorohexidine gluconate and sliced finely in Minimal Essential Medium supplemented with 10% fetal calf serum. The resultant tissue explants were treated as previously described (Baumgarten and Harley 1995 Comp. Biochem. Physiol. 110B, 37-46) and actively growing fibroblast cultures made available for the nuclear transfer process. Nuclear transfer was performed using the HMC technique (Vajta et al., 2003 Biol. Reprod. 68, 571-578) using slaughterhouse-derived bovine oocytes. Culture was performed in SOFaaci (Vajta et al., 2003 Biol. Reprod. 68, 571-578) medium supplemented with 5% cattle serum using WOWs (Vajta et al., Mol. Reprod. Dev. 50, 185-191). Two identical replicates were made with somatic cells of each species. After successful reconstruction, 57, 42 and 48 nuclear transferred and activated buffalo, bontebok and eland embryos were cultured, respectively. All except for 2 buffalo embryos cleaved; 22 (39%) developed to or over the 8-cell stage, and 2 (3.5%) of them to the blastocyst stage. All but 3 bontebok embryos cleaved, 17 (40%) developed to or over the 8-cell stage, but none of them reached the compacted morula or blastocyst stage. Sixteen (33%) of the eland embryos developed to or over the 8-cell stage with one (2%) reaching the blastocyst stage. In conclusion, buffalo, bontebok and eland embryos developed from reconstruction using their respective somatic cells combined with bovine cytoplasts, however, in vitro developmental ability to the blastocyst stage was limited. Additional basic research that establishes the regulative mechanisms involved with early preimplantation development together with optimising nuclear transfer techniques may have the potential to one day play a role in the conservation of critically endangered wildlife species.