Motoneurons and motoneuron-like pancreatic β cells arise from radial glia and ductal cells, respectively, both tube-lining progenitors that share molecular regulators. To uncover programs underlying motoneuron formation, we studied a similar, cell-division-independent transformation of the C. elegans tube-lining Y cell into the PDA motoneuron. We find that
lin-12/Notch acts through
ngn-1/Ngn and its regulator
hlh-16/Olig to control transformation timing.
lin-12 loss blocks transformation, while
lin-12(gf) promotes precocious PDA formation. Early basal expression of
ngn-1/Ngn and
hlh-16/Olig depends on
sem-4/Sall and
egl-5/Hox. Later, coincident with Y cell morphological changes,
ngn-1/Ngn expression is upregulated in a
sem-4/Sall and
egl-5/Hox-dependent but
hlh-16/Olig-independent manner. Subsequently, Y cell retrograde extension forms an anchored process priming PDA axon extension. Extension requires
ngn-1-dependent expression of the cytoskeleton organizers UNC-119, UNC-44/ANK, and UNC-33/CRMP, which also activate PDA terminal-gene expression. Our findings uncover cell-division-independent regulatory events leading to motoneuron generation, suggesting a conserved pathway for epithelial-to-motoneuron/motoneuron-like cell differentiation.