Animals transgenic for madd-4Ap::RFP express RFP in the commissural GABAergic and cholinergic motor neurons. RFP expression is weak in hatchlings and increases dramatically in only the cholinergic commissural motor neurons during the second larval stage, which is coincident with the period of larval muscle arm extension (Dixon and Roy, 2005). This pattern of commissural motor neuron-specific expression persists into adulthood and no other cells or stages express RFP from the
madd-4A promoter.