Fig. S1.

Characterisation of Sox2+ K8− Merkel cells. Horizontal wholemounts (A–D) showing (A, B) Sox2GFP expression (green) or (C, D) endogenous Sox2 (red) in skin sections labelled with antibodies to PDGFRa (red in A; white in B), K8 (green in C, D) or K14 (blue in C, D) and counterstained (A, B) with DAPI (blue). Sox2+K8+PDGFRa− cell is indicated by white arrow in B. Green arrow in C shows dermal sheath. White arrows in C, D show K8+K14+Sox2− cells. At E18.5 some weakly Sox2-positive cells are seen in the dermis (x) and around the hair follicles in the bulge area (*). These could potentially be nerve cells. (E, F) Wholemounts of E19.5 wild type touch domes immunolabelled for Sox2 (red) and K8 (green). Arrows show Sox2+K8− Merkel cells. Scale bar: 10 mm.