Abstract
Cell-cell interactions mediated by the Notch signaling pathway occur throughout C. elegans embryogenesis. These interactions have major roles in specifying cell fates and in tissue morphogenesis. The network of Notch interactions is linked in part through the Notch-regulated expression of components of the pathway, allowing one interaction to pattern subsequent ones. The Notch signal transduction pathway is highly conserved in animal embryogenesis. The REF-1 family of bHLH transcription factors are major targets of Notch signaling in the C. elegans embryo, and are distantly related to HES proteins that are targets of Notch signaling in Drosophila and vertebrates.
Highlights
Notch signaling in the C. elegans embryo interactions mediated by these receptors have been documented throughout embryonic and postembryonic development of C. elegans
The general mechanism of signal transduction, here called the Notch pathway for simplicity, has been elucidated primarily through studies in C. elegans and Drosophila, and is reviewed in detail in LIN-12/Notch signaling in C. elegans
A principal target of Notch signaling in the embryo is the ref-1 gene family, consisting of ref-1, hlh-25, hlh-26, hlh-27, hlh-28, and hlh-29 (Neves and Priess, 2005)
Summary
The first division of the fertilized egg produces two cells called AB and P (Figure 1). The requirement for GLP-1 in the interaction between ABp and P was deduced from later discoveries that (1) the P ligand was a Delta-like protein, (2) temperature-sensitive2GLP-1 alleles had an additional temperature-sensitiv2e period before the 12-cell stage, (3) glp-1 mutants had lineage defects in ABp as well as in ABa descendants, and that (4) preventing P from contacting ABp in wild-type embryos caused lineage defects similar to those seen in glp-1 mutants (Hutter and Schnabel, 1994; Mello et al, 1994; Moskowitz et al 1994). At the 24-cell stage, when TBX-37, -38 is first detectable, the REF-1 family is present at high levels in ABp and EMS descendants, but present at only low levels in the Notch-activated ABa descendants (Figure 4; Neves and Priess, 2005). The target(s) of the second Notch interaction that collaborates with TBX-37, -38 to induce expression of PHA-4, and promote mesodermal development, has not yet been identified
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