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Figure 3
(A and B) Anti-SV2 (A–A’’) or anti-5-hydroxytryptamine (5-HT) (B–B’’) immunostaining of the scale epidermis from an adult expressing an MC reporter. Insets of dotted regions show the punctate localization of SV2 and 5-HT staining in MCs (arrowheads), consistent with a vesicular localization. 96% of MCs (178/185) were SV2+. 98% of MCs (326/332) were 5-HT+. Cells analyzed from n=3 scales from N=2 adults (25–27 mm standard length [SL]). DAPI labels epidermal nuclei. (C) Scale epidermis from an adult expressing an MC reporter stained with AM1-43. 98% of MCs (90/92) were AM1-43+. Cells analyzed from n=6 scales from N=2 adults. Inset of dotted region shows puncta within an MC labeled by AM1-43 (arrowheads). AM1-43 has been reported to stain neurites innervating MCs in murine whisker vibrissae (Meyers et al., 2003). However, our AM1-43 staining regimen did not strongly label cutaneous axons, although we cannot exclude low levels of staining. (D) Scale epidermis from an adult expressing an MC reporter stained with hybridization chain reaction (HCR) probes against piezo2 and an anti-GFP antibody. 99% of MCs (310/314) were piezo2+. Cells analyzed from n=7 scales from N=2 adults. Arrowheads indicate examples of positive staining within an MC. Scale bars: 5µm.
Merkel cells (MCs) in the adult epidermis express neurosecretory and mechanosensory machinery.