Developmental Plasticity and Cellular Reprogramming in Caenorhabditis elegans

International audienceWhile Caenorhabditis elegans was originally regarded as a model for investigating determinate developmental programs, landmark studies have subsequently shown that the largely invariant pattern of development in the animal does not reflect irrevers-ibility in rigidly fixed cell fates. Rather, cells at all stages of development, in both the soma and germline, have been shown to be capable of changing their fates through mutation or forced expression of fate-determining factors, as well as during the normal course of development. In this chapter, we review the basis for natural and induced cellular plasticity in C. elegans. We describe the events that progressively restrict cellular differentiation during embryogenesis, starting with the multipotency-to-commitment transition (MCT) and subsequently through postembryonic development of the animal, and consider the range of molecular processes, including transcriptional and translational control systems, that contribute to cellular plasticity. These findings in the worm are discussed in the context of both classical and recent studies of cellular plasticity in vertebrate systems. Abstract 723 Cellular Plasticity 724 Definitions 724 Origin of the concept, relationship with cellular potential 725 Classical examples of cellular plasticity: toti-, pluri-, multi-or uni-potent cells and their demonstration 725 Developmental Programming: Regulative vs. Mosaic Models 726 Programming in the worm: classical view and fixed lineage 726 Early specification suggests plasticity is lost early 726 Founder cells are largely specified by apparent cell-intrinsic mechanisms at the time of their birth 726 Cleavage-arrest experiments and exclusivity of cell fate 727 Importance of DNA replication in specification 727 The C. elegans embryo: regulative development and early cellular plasticity clues 728 Nonlinear segregation of developmental potential 728 Continue