Probable transcriptional regulator that is required in neural development for the normal formation of sublateral cholinergic motor neuron processes. Plays a role in regulating the expression of acetylcholine transporter protein unc-17 in the sublateral processes. In particular, it is required in sublateral motor neurons for a left-right turning behavior that occurs during the lethargus phase of the normal sleep process called 'flipping'. During 'flipping' animals rotate 180 degrees about their longitudinal axis. Expressed in the 8 vulval muscles, 8-10 ventral neurons in the head and in the most posterior pharyngeal muscle cell, m8 (PubMed:9425137). Expressed in SIA, SIB and SMB sublateral motor neurons, and in muscles of the pharynx and vulva (PubMed:28244369). First expressed in the m8 pharyngeal muscle cell and in ventral head neurons in embryos 400 minutes after the first cell cleavage. Normal growth, coordination, egg-laying, mating, chemotaxis, pharyngeal pumping and VC neuron synapses as in wild-type animals (PubMed:9425137). Abnormal sleep behavior with mutant larvae displaying a reduced, if not absent, type of turning behavior called 'flipping' (PubMed:28244369). Irregular formation and extension of sublateral motor neuron processes (PubMed:28244369). Belongs to the NK-2 homeobox family.