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. Belongs to the NK-2 homeobox family.