Heterochromatin establishment in the context of genome-wide epigenetic reprogramming.

Heterochromatin at pericentric satellites, characterized by a specific chromatin signature and chromocenter organization, is of paramount importance for genome function. Re-establishment of this organization after fertilization takes place in the context of genome-wide epigenetic reprogramming. We review how the asymmetry in histone variants and post-translational modifications between paternal and maternal genomes and their respective pericentric heterochromatin domains evolve during early cleavage stages in mouse. We draw a parallel between these data and the burst of pericentric satellite transcription that occurs concomitantly with the dynamic reorganization of the pericentric domains into chromocenters in two-cell stage embryos. Based on this new angle, we propose that a crucial developmental transition at the two-cell stage allows chromocenter formation by involving non-coding satellite transcripts to trigger specific chromatin changes.