Essential signaling protein which has a major role in many developmental processes; involved in cell fate decisions that require cell-cell interactions (PubMed:3419531, PubMed:3000611). Probable membrane-bound receptor for putative ligands lag-2, apx-1, dsl-1 and osm-11 (PubMed:18036582, PubMed:18700817, PubMed:32053105, PubMed:3419531). Upon ligand activation, and releasing from the cell membrane, the lin-12/Notch intracellular domain (NICD) forms a transcriptional activator complex with lag-1 and lag-3 and regulates expression of various genes (PubMed:8343960, PubMed:7566091, PubMed:16197940, PubMed:10830967, PubMed:16530045, PubMed:18381292). Required for ventral cell fates in the postembryonic mesodermal lineage (M lineage) and in uterine precursor cells (PubMed:3419531, PubMed:18036582). Activity in cell fate decisions and tumorigenesis is negatively regulated by sel-10 (PubMed:9389650). Best known for involvement in cell-fate decisions during development, but also plays roles in other events (PubMed:10903169, PubMed:18599512, PubMed:21549604, PubMed:27661254). Regulates recovery from the dauer larval state (PubMed:18599512). Modulates chemosensory avoidance of octanol and quiescence during molting (PubMed:21549604). Promotes basement membrane mobility during tissue remodeling (PubMed:27661254). Involved in establishing left-right asymmetry during intestinal organogenesis (PubMed:10903169). May interact with dsl-1 (PubMed:18700817). May interact with lag-2 (PubMed:18700817). May interact with osm-11 (PubMed:18700817). Interacts with sel-10 (PubMed:9389650). When activated, the lin-12/Notch intracellular domain (NICD) can become a component of a complex consisting of at least the NICD, lag-1 and sel-8/lag-3 (PubMed:16530045, PubMed:18381292). The NICD probably facilitates ordered assembly of the ternary complex via allosteric interactions of its RBP-j associated molecule (RAM) domain with lag-1 (PubMed:16530045, PubMed:18381292). Localizes to the apical cell membrane of vulval precursor cells. Becomes localized to the nucleus during signal transduction. Expressed in the postembryonic mesodermal lineage (M lineage) at the 4-M to 8-M stages, at similar levels in both the dorsal and the ventral sides (PubMed:18036582). At the 10-M stage and later, expression becomes more restricted along the anterioposterior axis and gradually lost in the anterior M lineage cells, but retained in the posterior M lineage cells (PubMed:18036582). Upon binding its ligands, it is cleaved (S2 cleavage) in its extracellular domain, close to the transmembrane domain (By similarity). S2 cleavage is probably mediated by the metalloproteases adm-4 and sup-17 (PubMed:16197940). It is then cleaved (S3 cleavage) downstream of its transmembrane domain, releasing it from the cell membrane; S3 cleavage requires a multiprotein gamma-secretase complex, which may include presenilin sel-12 (PubMed:7566091). RNAi-mediated knockdown in cells of the pi uterine cell lineage results in impaired basement membrane mobility (PubMed:27661254). Knockdown on a glp-1 mutant background impairs octanol response when animals are shifted to the restrictive temperature (PubMed:21549604). Belongs to the NOTCH family.