Notch inhibition of RAS signaling through MAP kinase phosphatase LIP-1 during C-elegans vulval development

During Caenorhabditis elegans vulval development, a signal from the anchor cell stimulates the RTK/RAS/MAPK (receptor tyrosine kinase/RAS/mitogen-acti vated protein kinase) signaling pathway in the closest vulval precursor cel l P6.p to induce the primary fate. A Lateral signal from P6.p then activate s the Notch signaling pathway in the neighboring tells P5.p and P7.p to pre vent them from adopting the primary fate and to specify the secondary fate. The MAP kinase phosphatase LIP-1 mediates this lateral inhibition of the p rimary fate. LIN-12/NOTCH up-regulates lip-1 transcription in P5.p and P7.p where LIP-1 inactivates the MAP kinase to inhibit primary fate specificati on. LIP-1 thus Links the two signaling pathways to generate a pattern.