In Caenorhabditis elegans, the early embryo contains five somatic founder cells (known as AB, MS, E, C and D) which give rise to very different lineages. Two simply produce twenty intestinal (E) or muscle (D) cells each, whereas the remainder produce a total of 518 cells which collectively contribute in a complex pattern to a variety of tissues. A central problem in embryonic development is to understand how the developmental potential of blastomeres is restricted to permit the terminal expression of such complex differentiation patterns. Here we identify a gene,
lit-1, that appears to play a central role in controlling the asymmetry of cell division during embryogenesis in C. elegans. Mutants in
lit-1 suggest that its product controls up to six consecutive binary switches which cause one of the two equivalent cells produced at each cleavage to assume a posterior fate. Most blastomere identities in C. elegans may therefore stem from a process of stepwise binary diversification.AD - Max-Planck-Institut fur Biochemie, Martinsried, Germany.FAU - Kaletta, TAU - Kaletta TFAU - Schnabel, HAU - Schnabel HFAU - Schnabel, RAU - Schnabel RLA - engPT - Journal ArticleCY - ENGLANDTA - NatureJID - 0410462SB - IM