Required for specification of the AIA and AIY interneurons and the NSM neurons. Positively regulates the expression of a number of genes including ceh-23, kal-1, hen-1, ser-2, unc-17 and sra-11 in AIY interneurons and cat-4, flp-4, bas-1, ptps-1 and mgl-1 in NSM neurons. Also acts in an autoregulatory feedback loop to maintain its own expression. Plays a role in the thermotactic response, olfactory imprinting, regulation of longevity, control of dauer formation and axon outgrowth and pathfinding. Not required for normal chemosensory behavior. Expressed in the AIA, AIN and AIY interneurons, and in the NSM neurons. Expressed also in ADL and ASI sensory neurons in 60-70% of L2 larvae. Expression is also detected in head muscles of embryos and some early larvae but not late larvae or adults. Expressed during embryogenesis and persists through to adulthood in AIY interneurons. Expressed at L1 stage and through adulthood in AIA and NSM neurons. Expression is detected in head muscles of all 1.5 and 2-fold embryos, 47% of embryos just before hatching and 6% of early larvae with no expression in head muscles of late stage larvae or adults. Animals are cryophilic and move toward lower temperatures irrespective of cultivation temperature in contrast to wild-type animals which move toward their cultivation temperature when placed on a temperature gradient. AIA and AIY interneurons display defective neurite morphology. NSM neurons display loss of or reduced expression of a number of terminal identity markers including cat-4, flp-4, bas-1, ptps-1 and mgl-1. Reduced expression of ceh-23, kal-1, C36B7.7, ser-2, unc-17 and sra-11 is observed in AIY interneurons. Preexposure to odorants fails to leave an olfactory imprint. Mean lifespan is reduced by 10% with decreased pharyngeal pumping and increased intestinal autofluorescence caused by lysosomal deposits of lipofuscin, indicative of cellular damage and aging. Formation of very few dauers in starvation conditions. No defects observed in brood size, egg number or chemotactic behavior toward volatile chemicals.