Transcription factor required for the formation of correct projections from nociceptive sensory neurons to the dorsal horn of the spinal cord and normal perception of pain. Interacts with RGMB. Expressed in the dorsal horn of the spinal cord and dorsal root ganglia. Isoform 1 is higher expressed than isoform 2 both in the dorsal root ganglia and in the spinal cord. Isoform 2 is exclusively localized in neurons primarily involved in the processing of the pain somatosensory modality. First detected at 12.5 dpc in newly generated neurons adjacent to the ventricular zone of the dorsal spinal cord. Later expressed in lateral region of the dorsal spinal cord and dorsal root ganglia at 13.5 dpc with increased levels at 15.5 dpc. Defects in the projection pattern of nociceptive sensory neurons to the dorsal horn of the developing spinal cord leading to reduced sensitivity to painful stimuli. They die within 3 weeks of birth. Mice lacking Drgx exhibit reduced expression of Rgmb in dorsal root ganglion sensory neurons. Belongs to the paired homeobox family.