Na_V1.7  (Scn9a) is predominantly expressed in dorsal root ganglions (DRG) of the peripheral nervous system. Dominant gain-of-function mutations in the Na_V1.7 gene are associated with erythermalgia (a rare autosomal disease characterized by sporadic burning pain accompanied by redness and heat in the extremities). Loss-of-function mutations in Na_V1.7 channels, lead to complete ablation of pain perception in humans. Scn9a is a major therapeutic target for pain.