Probable secreted Notch ligand involved in the mediation of Notch signaling (PubMed:14960273, PubMed:18700817). Involved in the lin-12/Notch pathway-mediated signaling of cell fate in vulval precursor cells (VPCs), acting redundantly with lag-2, apx-1 and osm-11 (PubMed:14960273, PubMed:18700817). May also be involved in glp-1/Notch signaling (PubMed:14960273). May interact with lin-12/Notch receptor. Causes adjacent vulval precursor cells (VPCs) to adopt altered cell fate; phenotype exacerbated when combined with simultaneous RNAi-mediated knockdown of apx-1 and lag-2, and further worsened on lin-15 mutant background (PubMed:14960273). Severe vulval precursor cell (VPC) fate abnormalities, vulval defects and failure to up-regulate lip-1 expression, on an osm-11 mutant background (PubMed:18700817).