Highlights d Phox2a is transiently expressed in embryonic anterolateral system (AS) spinal neurons d Phox2a AS neuron development reflects AS neuron diversity d Spinal Phox2a knockout causes aberrant AS connectivity and nociceptive defects d Human and mouse embryonic spinal Phox2a neurons are similar

Highlights d Activation of CR neurons elicits mechanical allodynia and increased spontaneous pain d CR neurons engage pain processing sites such as the parabrachial nucleus and the amygdala d CR neurons directly engage spinoparabrachial neurons to elicit nocifensive responses d Reduced excitatory output from CR neurons impairs sensitivity to painful stimuli

Avoidance of environmental dangers depends on nociceptive topognosis, or the ability to localize painful stimuli. This is proposed to rely on somatotopic maps arising from topographically organized point-to-point connections between the body surface and the CNS. To determine the role of topographic organization of spinal ascending projections in nociceptive topognosis, we generated a conditional knockout mouse lacking expression of the netrin1 receptor DCC in the spinal cord. These mice have an increased number of ipsilateral spinothalamic connections and exhibit aberrant activation of the somatosensory cortex in response to unilateral stimulation. Furthermore, spinal cord-specific Dcc knockout animals displayed mislocalized licking responses to formalin injection, indicating impaired topognosis. Similarly, humans with DCC mutations experience bilateral sensation evoked by unilateral somatosensory stimulation. Collectively, our results constitute functional evidence of the importance of topographic organization of spinofugal connections for nociceptive topognosis.