(a) Photomicrographs of cutaneous sensory nerves in control mouse skin, labeled with PGP9.5, showing normal organization of sensory nerves into deep dermal plexus (double-headed arrows), radial fibers (large arrows), subepidermal plexus (small arrows), and epidermal free nerve endings (arrowheads). (b) Cutaneous innervation of Egfr null skin. Note the increased density and absence of normal pattern. The normal plexiform arrangement was replaced by a rete of nerves throughout the superficial layer of the dermis. (c) Acetylated tubulin immunolabeled sensory nerves of the wild-type skin showing the normal pattern of deep dermal plexus (double-headed arrows), subepidermal plexus (small arrows), and epidermal free nerve branches (arrowheads). (d) Acetylated tubulin immunolabeling of the cutaneous nerves of Egfr null showing consistently denser and disorganized pattern of sensory fibers. Note that epidermal and follicular keratinocytes (green cells) are immunostained for keratin 14 (K14) in (c) and (d). (e) Normal innervation pattern of the wild-type skin as revealed by GAP-43 immunolabeling. (f) Cutaneous innervation of Egfr null showing denser and disorganized pattern with GAP-43 immunolabeling. Scale bar is 100 μm in all figures.