embryonic rosettes · Investigating embryonic development at the time of implantation using embryos and ES cells

Investigating embryonic development at the time of implantation using embryos and ES cells

Nuclear organization during the pre-implantation development of the mouse embryo displays features necessary for the reprogramming of chromatin. These involve histone modifications, nuclear repositioning, and the reorganization of chromatin associated with activation of specific genes. These changes occur in the embryo after fertilization and are necessary for the establishment of the three lineages of the blastocyst: the pluripotent epiblast (EPI) that gives rise to the future body of the animal and which together with extra-embryonic primitive endoderm (PE) is derived from the inner-cell-mass (ICM), and the trophectoderm (TE), the other extra-embryonic tissue that forms the placenta. It has been shown that differences in epigenetic modification between early blastomeres are linked to their fate. Therefore, cells with increased histone H3 arginine 26 methylation (H3R26me2), considered as an activating mark, show higher expression of a subset of pluripotency genes that include Nanog, Sox2 or Oct4, and are destined to contribute to embryonic rather than extra-embryonic tissues . Differential levels of histone H3R26me2 between 4-cell blastomeres are mediated by the heterogeneous activity of the histone coactivator associated arginine methyltransferase 1 (CARM1). However, nuclear organization has never been carefully examined during early mammalian development at the stages leading to establishment of ICM and TE.

Data: CORDIS, © European Union