Cell signals allow the expression of a pre-existent neural pattern in C. elegans.
In C. elegans, a simple pattern develops within a row of epidermal precursor cells, V1-V6. One cell, V5, gives rise to a neuroblast called the postdeirid neuroblast, while the other V cells produce epidermal cells instead. Here we describe experiments suggesting that in order for V5 to produce the postdeirid it must be in close or direct contact with neighboring V cells. Signaling between V cells is required for the formation of the neuroblast; however, which of the V cells can make a postdeirid is not determined by these signals but rather by the action of the homeotic lin-22 and pal-1 genes. These genes prevent V cells in specific body regions from responding to intercellular signals and producing postdeirids. This is a clear example of cell signals playing a permissive rather than an instructive role in neuroblast induction.
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0554.
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Waring
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Wrischnik
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Kenyon
D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000235:genetics; D004627:Embryonic Induction / Q000502:physiology*; D005801:Genes, Homeobox / Q000502:physiology; D009420:Nervous System / Q000196:embryology*; D012867:Skin / Q000196:embryology