The generation of cloned embryos by somatic cell nuclear transfer (SCNT) into enucleated mature oocytes is inefficient because epigenetic reprogramming is limited in these embryos. However, treatment of somatic nuclei with a cytoplasmic extract from germinal vesicle (GV) stage oocytes before SCNT is known to improve the efficiency of cloned mouse production. Now (p. ), Hong-Thuy Bui, Jin-Hoi Kim and co-workers use an extract from GV stage pig oocytes (GVcyto-extract) to investigate epigenetic reprogramming events in pig fibroblasts. The researchers report that fibroblasts treated with GVcyto-extract express the stem cell-associated proteins Oct4 and Nanog and re-differentiate into three primary germ cell layers in vitro and in vivo. Moreover, the use of donor nuclei treated with GVcyto-extract, they report, increases the number of high quality SCNT-generated blastocysts that exhibit levels of histone H3-K9 methylation and acetylation and Oct4 and Nanog expression similar to those in embryos fertilised in vitro. These results suggest that a combination of epigenetic reprogramming techniques might improve the efficiency of development in SCNT-generated embryos.
