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Figure 2
(A) Lateral confocal micrograph of the scale epidermis from an adult expressing an MC reporter immunostained for peripheral axons (zn-12). (B) Lateral confocal micrograph of the scale epidermis showing that somatosensory peripheral axons (Tg(p2rx3b:EGFP)) innervate MCs. Inset of dotted region shows axonal varicosities adjacent to an MC (arrowheads). (C) Quantification of MC innervation in the scale epidermis (17–30 mm standard length [SL]). Each dot represents measurements from an individual scale. Innervation frequencies: zn-12, 91% (284/311 cells; N=3 adults); Tg(p2rx3a>mCherry), 86% (196/228 cells; N=4 adults); Tg(p2rx3b:EGFP), 99% (225/228 cells; N=4 adults); Tg(trpa1b:EGFP), 96% (217/225 cells; N=9 adults). Error bars represent 95% CIs. (D–F) High-magnification confocal micrographs showing examples of somatosensory axons forming extended, ring-like contacts with MCs within the scale epidermis. (G) Three-dimensional (3D) reconstruction of an axon (zn-12 immunostaining, arrowheads) forming a bouton-like ending (asterisk) that terminates in close proximity to an MC. DAPI staining labels epidermal nuclei. (H) 3D reconstruction of a single somatosensory axon (Tg(p2rx3a>mCherry)) that forms en passant-like contacts (asterisks) with multiple MCs. Scale bars: 10 μm (A and B), 5 μm (D–H).
Somatosensory axons innervate Merkel cells (MCs) in the adult epidermis.