May be involved in regulating the specificity of expression of the catecholamine biosynthetic genes. Acts as a transcription activator/factor. Could maintain the noradrenergic phenotype. Expressed in sympathetic superior cervical ganglia and in noradrenergic, dopamine beta-hydroxylase (DBH)-positive tissues. Not expressed in brain. Expressed at E18 day in sympathetic ganglia. Belongs to the paired homeobox family.