In all lines, expression of
unc-3::GFP was first observed in late stage embryos (3-fold) in neurons of the ventral cord. In L1 larvae, 16 cells were counted that expressed
unc-3::GFP among the 22 embryonic motor neurons present in the ventral cord at this stage. By late L1 and early L2, when 57 new motor neurons are added to the ventral cord, an increase was observed in the number of GFP-positive cells. In two lines expressing GFP from an extrachromosomal array, there are up to 41 ventral cord motor neurons expressing the reporter at similar intensity. In the integrated line examined, the 23 VA and VB motor neurons expressed GFP at high levels, while 3 strongly staining and up to 11 additional faintly expressing cells were also detected. High levels of expression were maintained in these neurons through the L3 stage, but diminished in later stages. No GFP expression was observed in the ventral cord of a majority of adult worms.