Practice question

Vulval development provides model for lateral inhibition via Notch. Anchor cell secretes LIN-3 EGF inducing P5.p-P7.p to become vulval precursor cells. Among these, P6.p receiving highest LIN-3 dose adopts primary fate and expresses DSL ligands LAG-2, APX-1, DSL-1. These activate LIN-12 Notch receptor in neighboring P5.p and P7.p, triggering transcription of secondary fate genes lip-1, lst genes and repressing primary fate gene lin-39 hyperactivation. LIN-12 signaling thus ensures only one central cell becomes primary, flanking cells become secondary, preventing excessive primary lineage formation, central mechanism of lateral signaling patterning.