No abstract

No abstract

Parthenogenesis is an activation process of oocytes that occur without the participation of sperm. Evidence suggests that normal development of embryos requires proper expression of several imprinted genes inherited from both the paternal and maternal genomes. Compared to gene expression, histone modifications and chromatin remodeling are not well-documented. In this research, by using immunofluorescence staining for several developmental-associated histone modifications, we investigated whether epigenetic impairments in parthenogenetic embryos act as constraints for proper development. At early stages, fertilized embryos exhibited high methylation of histone H3 at lysine 9 (Me-H3-K9) and Heterochromatin Protein 1 (HP1) present in the maternal chromatin, while paternal chromatin showed weaker HP1 signals. We found that at the two-cell stage in fertilized embryos, HP1, initially detected around the nucleolus, colocalized with chromocenters at one pole of the blastomere, while parthenotes showed a diffused distribution pattern of HP1 throughout the entire nucleoplasm. At the four-cell stage, methylation of histone H3 at arginine 26 (Me-H3-R26) increased at nascent RNA repression sites in fertilized embryos, while parthenotes recorded weaker signals throughout the nucleoplasm, suggesting differences in pluripotency of the ICM cells between the two types of embryos. Moreover, at the blastocyst stage, we observed that the acetylation level of histone H4 at lysine 12 (Ac-H4-K12) was significantly decreased in parthenogenetic ICM compared to that in its fertilized counterpart. To summarize, differences in epigenetic modifications correlating with paternal chromatin’s capacity to regulate nascent RNA repression may contribute to aberrant development and lineage allocation in mouse parthenogenetic embryos.

Genomic reprogramming factors in the cytoplasm of mature oocytes could be reprogrammed somatic cell cells to totipotency cells and full-term development (cloned animals). Since then, this technique has been considered an important toot not only for animal reproduction but also for regenerative medicine, concervation of endangered species, and for study of genes function and cell biology. Moreover, in order to produce nuclear transfer embryonic stem (ntES) cells using somatic cell nuclear transfer (SCNT), the SCNT technique requires donated fresh oocytes, which raises ethical problems for production in human cloned embryo. For this reason, the use of induced pluripotent stem (iPS) cells for genomic reprogramming and for regenerative medicine is currently a hot topic in this field. However, the use of iPS cells for human therapy by the technique of retroviruses used to insert the pluripotent genes into somatic cells could cause tumors in tissues grown from the host iPS cells. Recently, we found that genomic reprogramming factors in the cytoplasm of pig germinal vesicle (GV)-stage oocytes has been shown to improve the efficiency of producing cloned mouse offspring and could reprogram pig fibroblasts to stem-like cells. In this talk, we will discuss whether pig GV cytoplasmic extract could induce pluripotent stem cells from mouse fibroblast cells (interspecies reprogramming). We first established stem-like cells from mouse fibroblast cells treated with GV oocytes extracted (gviPS cells). We demonstrated that reactivation of Oct4 promoter in mouse Oct4-GFP fibroblast cells at day 10 after treated with pig GV oocyte cytoplasmic extract and the formation of colonies is observed at 3 weeks after treatment. In addition, mouse gviPS cells reprogrammed with pig GV cytoplasmic extract can in vitro re-differentiate into neuron-like cells. Interestingly, mouse gviPS cells injected into embryos of different mouse strain could be produced chimeric mice.

No abstract