The cell cycle of early mammalian embryos: lessons from genetic mouse models.

Genes coding for cell cycle components predicted to be essential for its regulation have been shown to be dispensable in mice, at the whole organism level. Such studies have highlighted the extraordinary plasticity of the embryonic cell cycle and suggest that many aspects of in vivo cell cycle regulation remain to be discovered. Here, we discuss the particularities of the mouse early embryonic cell cycle and review the mutations that result in cell cycle defects during mouse early embryogenesis, including deficiencies for genes of the cyclin family (cyclin A2 and B1), genes involved in cell cycle checkpoints (Mad2, Bub3, Chk1, Atr), genes involved in ubiquitin and ubiquitin-like pathways (Uba3, Ubc9, Cul1, Cul3, Apc2, Apc10, Csn2) as well as genes the function of which had not been previously ascribed to cell cycle regulation (Cdc2P1, E4F and Omcg1).