The
unc-4 gene is expressed in several ventral cord motor neurons: the DA cells in the embryo, the VA cells in first and second larval stages (L1 and L2), and the VC cells in L4 larvae and young adults. The number of ventral cord motor neurons expressing detectable GFP from the
unc-4 promoter increases as animals develop, with adults having many more fluorescent cells than accounted for by the VC cells.