The lin-3/let-23 pathway mediates inductive signalling during male spicule development in Caenorhabditis elegans.
During Caenorhabditis elegans male spicule development, four pairs of precursor cells respond to multiple positional cues and establish a pattern of fates that correlates with relative anterior-posterior cell position. One of the extracellular cues is provided by the F and U cells, which promote anterior fates. We show that the genes in the lin-3/let-23 signalling pathway required for hermaphrodite vulval induction also mediate this F/U signal. Reduction-of-function mutations in lin-3, let-23, sem-5, let-60 or lin-45 disrupt the fate of anterior cells. Likewise, activation of the pathway with ubiquitously produced signal results in posterior cells inappropriately adopting the anterior fates even in the absence of F and U. We have further used this genetic pathway to begin to understand how multiple positional cues are integrated to specify cell fate. We demonstrate that lin-15 acts in spicule development as it does in vulval induction, as a negative regulator of let-23 receptor activity. A second extracellular cue, from Y.p, also acts antagonistically to the lin-3/let-23 pathway. However, this signal is apparently integrated into the lin-3/let-23 pathway at some step after lin-45 raf and is thus functionally distinct from lin-15. We have also investigated the role of lin-12 in forming the anterior/posterior pattern of fates. A lin-12 gain-of-function defect is masked by redundant positional information from F and U.
Chamberlin
H M
HM
Howard Hughes Medical Institute, California Institute of Technology, Pasadena 91125, USA.
Sternberg
P W
PW
D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D004627:Embryonic Induction / Q000235:genetics*; D017238:Genes, Helminth; D005837:Genitalia, Male / Q000196:embryology; D008297:Male; D009024:Morphogenesis / Q000235:genetics; D010641:Phenotype