Determinants of blastomere identity in the early C. elegans embryo.

Genetic and molecular studies of development in Caenorhabditis elegans have identified regulators that appear to control pattern formation in the cellularized nematode embryo. Two genes, skn-1 and pie-1, are required for specifying the different identities of two sister blastomeres in a 4-cell embryo, called P2 and EMS. The skn-1 gene encodes a DNA binding protein that may control blastomere development by regulating transcription in EMS and its descendants. ABa and ABp, the other two sisters in a 4-cell embryo, are influenced to develop differently by cell signaling events that require the two genes apx-1 and glp-1. In this review, I summarize evidence that some or all of these genes may encode embryonic determinants of blastomere identity.