Nuclear transplantation using bovine primordial germ cells from male fetuses.

The developmental potential of nuclei of bovine gonial cells was investigated by nuclear transfer. Gonial cells were collected from male fetuses at about 175 days post coitum (p.c.). They were fused with enucleated oocytes; reconstituted embryos were cultured in vitro for 7 days. Embryos reaching the compacted morula or blastocyst stage were either fixed for cell counting or transferred into recipients. Out of 115 oocyte-gonia fusions, 101 (87.8%) gave rise to cleaved embryos at Day 3 and 26 (22.6%) had reached the 8-cell stage. At Day 7, 1 (1%) developed to the morula stage and 5 (4%) reached the blastocyst stage. Three blastocysts were fixed and showed normal cell numbers (135; 90; 76 cells). Three blastocysts and one morula were transferred in four recipients; two recipients were pregnant at Day 21 but only one was positive at Day 35 p.c.; this last one aborted around Day 40 p.c. No conceptus was collected. These results indicate that gonial cell nuclei can be partially reprogrammed; they are able to develop into blastocysts and to initiate gestation. However, more experiments will be necessary to prove the nuclear totipotency of bovine gonial cells