Figure 4.

Expression of SAI LTMR endings and other nerve endings in the glabrous and hairy skin of male Merkel cell-deficient and control mice. A–D, Whole-mount immunostaining for tdTomato (red), K8 (green), and K17 (blue) in the glabrous (A) and hairy (B) skin from control Cre-negative Atoh1^fl/fl;TrkC^tdtomato mice, and the glabrous (C) and hairy (D) skin from K14^Cre+;Atoh1^fl/fl;TrkC^tdtomato mice. Insets, Expanded view of TrkC^tdtomato+ nerve endings. Long structures in K8 staining (B,D) are autofluorescent or crossreacting hair shafts. Compact structures (arrows in B) are Merkel cells. Scale bar, 100 µm. E–H, Whole-mount staining for CGRP (blue) and tdTomato (red) in the glabrous (E) and hairy (F) skin of control mice, and the glabrous (G) and hairy (H) skin of K14^Cre+;Atoh1^fl/fl;TrkC^tdtomato mice, respectively. Scale bar, 100 µm. I, Quantification of the number of TrkC⁺ nerve terminals in hind paw glabrous skin of K14^Cre+;Atoh1^fl/fl;TrkC^tdtomato (n = 9) and control (n = 9) mice. Data are mean ± SEM. Unpaired two-tailed Student's t test. J, Quantification of the total branch length per TrkC⁺ nerve terminal complex in glabrous hind paw skin from K14^Cre+;Atoh1^fl/fl;TrkC^tdtomato (n = 9) and control (n = 9) mice. Data are mean ± SEM. Unpaired two-tailed Student's t test. K, Whole-mount immunostaining for tdTomato in hairy skin of control (left) and K14^Cre+;Atoh1^fl/fl;TrkC^tdtomato (right) mice. Insets, Amplified view of TrkC^tdtomato+ circumferential nerve endings, which are presumably field LTMRs. Scale bar, 100 µm.