65 BLASTOCYSTS DERIVED FROM ADULT FIBROBLASTS OF RHESUS MONKEY (MACACA MULATTA) USING INTERSPECIES SOMATIC CELL NUCLEAR TRANSFER

Abstract

Interspecies somatic cell nuclear transfer (iSCNT) has alternatively chosen in primate SCNT because of the difficulty in collecting enough oocytes for research. The purpose of this experiment is to produce iSCNT-derived blastocysts using enucleated cow (Bos taurus) metaphase II oocytes and adult rhesus monkey (Macaca mulatta) fibroblasts. Ear skin tissueofrhesus monkey (male, 6 years old) was collected by biopsy and fibroblasts were isolated. Immature COCs from cow ovaries were collected and matured in vitro in TCM-199. Squish enucleation was done in the presence of bisbenzimide and cytochalasin B. After enucleation, a single rhesus monkey somatic cell was injected into the perivitelline space of an enucleated oocyte through the slit in the zona pellucida made during enucleation. Subsequently, the rhesus monkey somatic cell and cow oocyte membranes were electrically fused. The nonactivated interspecies cloned couplets were cultured for 2 h to allow reprogramming to occur. Then, couplets were activated using a 2-step protocol consisting of treatment with 5 μM ionomycin for 4 to 5 min and subsequently with 2mM 6-DMAP for 4 h. Activated iSCNT embryos were cultured for 10 days inmodified SOF with various conditions (at 37 to39°C, 5 to 5.5% CO₂ and 5 to 20% O₂) to examine the effects ofIVC conditions. As a results, most embryos were arrested at the 8- to 16-cell stage and only 3 blastocysts were derived from rhesus monkey iSCNT. The blastocyst developmental rate was 0.26% generated from the total IVC activated interspecies embryos (n = 1153). Among the 3 blastocysts, 2 of them were used for counting nuclear number using bisbenzimide staining. The nuclear number of the 2 iSCNT-derived blastocysts was 51 and 24, respectively. The other iSCNT-derived blastocyst was used for analyzing mitochondrial (mt)DNAto confirm that it contained both cow and rhesus monkey mtDNA. As a result, mtDNA from both rhesus monkey and cow were detected inPCR analysis. The band intensity was more dominant for cow mtDNA than for rhesus monkey mtDNA. Although the blastocyst developmental rate is extremely low, it is confirmed that two phylogenetically distant species including primate could develop in vitro until the blastocyst stage by iSCNT. The in vitro developmental system of this rhesus monkey iSCNT-derived blastocysts provides a platform for further improvement of developmental rate and quality of rhesus monkey iSCNT-derived blastocysts. It also provides an opportunity to establish rhesus monkey iSCNT-derived embryonic stem cell lines for study of rhesus monkey nucleus and cow mitochondria interaction mechanisms during early developmental stages.

This study was financially supported by the Korean MEST, through the BK21 program for Veterinary Science, and SNU foundation (Benefactor; RNL Bio).