ChR2 expression in DRGs is ubiquitous among all sensory subtypes (Supplementary Figures 1A, B), however, previous studies reported CCL21 expression specifically in small diameter TRPV1+ nociceptors after peripheral nerve injury (13, 34), so we hypothesized that this CCL21 increase after optogenetic stimulation could be specific of this neuronal subtype. This evidence concerns the gene CCL21 and peripheral nerve injury.