Involved in the development of several major noradrenergic neuron populations, including the locus coeruleus. Transcription factor which could determine a neurotransmitter phenotype in vertebrates. Enhances second-messenger-mediated activation of the dopamine beta-hydrolase and c-fos promoters, and of several enhancers including cAMP-response element and serum-response element. Interacts with TRIM11. Expressed in neuroblastoma, brain and adrenal gland. The disease is caused by variants affecting the gene represented in this entry. Disease susceptibility is associated with variants affecting the gene represented in this entry. Belongs to the paired homeobox family.