SCN9A and hereditary sensory and autonomic neuropathy: Given the finding of reduced IENFD in CIP patients and a previous report linking NaV1.7 gain-of-function mutations to altered neurite outgrowth of sensory neurons in vitro (Persson et al., 2013), we sought to test whether iPSC nociceptors lacking NaV1.7 had a defect in neurite outgrowth.