Fig. 1. Working hypothesis summarizing the relationships of molecular events that drive CR. This synopsis is drawn from several recent review articles (Swynghedauw, 1999; Bogoyevitch, 2000; Akazawa and Komuro, 2003; Sugden, 2003; Knöll et al., 2003; Barki-Harrington and Rockman, 2003; Katsumi et al., 2004). The hypothesis is based on the sequence of events proposed elsewhere (MacLellan and Schneider, 2000). It includes a mechanical trigger, a cytoplasmic cascade, and then a series of phosphorylations/dephosphorylations that finally activate several transcription factors. These factors are known to act synergistically in a combinatorial fashion. It is hypothesized that (i) the foetal reprogramming depends upon transcription factors expressed during embryogenesis, and (ii) non-specific gene activation is a consequence of growth factor secretion. The scheme does not include autocrine/paracrine factors. The functions of the immediate early genes are unknown; several of them are not translated into proteins (Snoeckx et al., 1991).