Wilhelm bernhard workshop on the cell nucleus

CHROMATIN


DYNAMICS OF NUCLEAR COMPARTMENTS DURING EARLY EMBRYOGENESIS IN THE MOUSE

Martin C.¹, Zatsepina O.³, Migné C.¹, Chebrout M.¹, Beaujean N.¹, Zink D.⁴ and Debey P^1,2.

¹ UMR Biologie du Développement de Reproduction, INRA, Jouy-en-Josas, France, ²USM 503, Département Régulation Développement et Diversité Moléculaire, Muséum national d’Histoire naturelle, Paris, France, ³A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russia, and ⁴Department Biologie II, LMU München , Germany
The beginning of embryonic life is characterized by major structural remodelling of nuclear compartments, together with the progressive establishment of nuclear activities, namely RNA polymerases II (pol II) and RNA polymerase I (pol I). We have earlier shown that, in the mouse embryo, pol II activity starts at the beginning of the first celle cycle, whereas pol I starts at the end of the second cell cycle (Bouniol et al., 1995; Zatsepina et al., 2002). Using different markers of centromeres and centromeric heterochrochromatin, in combination with labeling of DNA which is replicated in late S phase of the first cell cycle, we analyze the dynamics of chromosomal domains during the first cell cycles. We show a complete redistribution of chromosomal domains, mainly occuring between the first and second, and later between the second and third cell stages, and involving also the nucleolus-like bodies (NLBs). Differential recruitment of the hetero-chromatin proteins HP1 and HP1 occur during the same period. Similar, though not identical, changes occur in somatic cell nuclei transfered to activated oocytes, such as performed in “cloning” experiments.

References:

Bouniol et al : Exp Cell Res 218, 57-62, 1995

Zatsepina et al: Dev. Biol. 253, 66-83, 2002