Fig. 6. Immunofluorescence images of follicle innervation labeled with anti-PGP or anti-NF200 in P0 Ntf3^–/–, trkC_K^–/– and trkC_E^–/– mice. In addition to axons (arrows), anti-PGP labels Merkel endings and cells (white arrowheads), and anti-NF200 labels only Merkel endings (open arrowheads). Brackets span locations where Merkel endings are missing. (A,B) Newborn Ntf3^–/– have only a few Merkel cells and a few fragmented axons. Anti-NF200 labels only a few axons and rarely any endings. (C,D) Newborn trkC_K^–/– have fewer Merkel endings and cells than normal, but much more than Ntf3^–/–. Most Merkel cells have endings. (E,F) Newborn trkC_E^–/– lack any detectable Merkel endings or cells labeled with either anti-PGP or anti-NF200. Both trkC_K^–/– and trkC_E^–/– have lanceolate endings (open arrows) and reticular endings (broad arrows) supplied by large caliber myelinated axons as well as epidermal endings (curved arrows) supplied by C-fibers that are not dependent upon intact kinase (Fundin et al., 1997) or trkC_Tr. However, these other endings are severely depleted in the absence of NT3 which, in these cases, may normally signal through trkA_K or trkB_K (Fundin et al., 1997; Rice et al., 1998). Scale bar: 50 µm.

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