Acts in a cell autonomous fashion to specify the properties of the sensory ray and non-autonomously in the choice of hypodermal versus neuroblast cell fate. Expressed from the onset of gastrulation, beginning with the dorsal hyp7 cells. Subsequently detected in other cell types including hypodermal cells, neuronal cells near the pharyngeal bulbs, neurons along the ventral nerve cord, the AVM, HOA, HOB, PLM and VA3 neurons, some body wall muscles, and the ray cells. During the L4 stage, expressed within neuron A of all ray cells, neuron B of rays 3 and 6, and the structural cell of ray 6. Transcription is repressed by heat shock. In the male tail, ray precursor cells show altered fates. Conical sensory ray 6 is absent as it appears to fuse with ray 4. Males show reduced body length and uncoordinated movement in a backwards locomotion. Hermaphrodites produce a reduced brood size due to a decreased number of laid eggs. Belongs to the mab-21 family.