Abstract

Somatic cell nuclear transfer (SCNT) has been successfully performed in various mammals including sheep, cow, pig, and mouse using a variety of somatic cell types as nuclear donors. Several reports of livestock SCNT indicate that fetal fibroblasts are superior to adult fibroblasts as donor cells. In canine SCNT, however, only adult ear fibroblasts have been used as donor cells (Lee et al. 2005 Nature 436, 641; Jang et al. 2007 Theriogenology 67, 941–947). Accordingly, in the present study, we evaluated the ability of canine fetal fibroblasts to support fetal development to term after nuclear transfer. For SCNT, in vivo-matured oocytes flushed (approximately 72 h after ovulation) from the oviducts of six estrus females were used. Donor cells (fetal fibroblasts) were isolated from the fetus of a beagle bitch obtained at 28 days after artificial insemination. Before using fetal fibroblasts as donor cells, sex was determined by SRY gene detection using PCR. Oocytes were enucleated, microinjected with a female fetal fibroblast, fused by electrical stimulation, and activated chemically (Jang et al. 2007). A total of 50 cloned presumptive embryos were transferred (Day 0) into the oviducts of two naturally synchronous recipient bitches. One pregnancy, detected by ultrasonography on Day 23, was maintained to term and two healthy female puppies weighing 250 and 260 g were born by natural delivery on Day 60. They were genotypically identical to the donor cells, and had phenotypically similar black and white coat color patterns. Analysis of their mtDNA distribution showed that mtDNA in the two cloned beagles originated from one of the six oocyte donor dogs. In conclusion, our results demonstrate the potential of using fetal fibroblasts to facilitate nuclear transfer in the dog. The cloned beagle dogs, which had identical nucleus and mitochondrial DNA, will be provided for biomedical research as bioresources.