Jun SC deletion interferes with neuronal survival and regeneration. (A and B) Recovery of whisker hair movement (WHM). (A) WHM was scored on a scale of 0 (no movement) to 3 (strong, normal movement); see Materials and methods for details. The data points show mean ± SEM for Jun^ΔSC (n = 6) and their littermate controls (n = 9). *, P < 0.05 in unpaired two-tailed t test in this and all the following graphs. (B) WHR recovery index (WHM RI) based on area under the curve (AUC) for each individual animal that was assessed in A. Jun^ΔSC show a very significant poorer overall recovery with 0.82 ± 0.09 for Jun^f/f animals and 0.31 ± 0.03 for Jun^ΔSC (mean ± SEM); P < 0.05, Student’s t test. (C–G) Peripheral target reinnervation of the whisker pad is reduced in the absence of Jun in SC; same animals as in A and B. (C) Ratio of retrogradely labeled facial motoneurons on the axotomized (Ax) versus contralateral (Co) side after application of FG to both whisker pads, 28 d after facial cut followed by 72 h survival. (D–G) Representative images of retrograde labeling with FG. On the uninjured (contralateral) side, retrogradely labeled facial motoneurons are mainly found in the lateral subnucleus (D and F), but appear randomly distributed throughout the nucleus after cut (E and G). Note the sharp decrease in the number of labeled neurons on the axotomized side in mutant Jun^ΔSC (n = 6) and their littermate controls (n = 9) (G) compared with control (E) animals. (H and I) Nissl-stained brainstem coronal sections 31 d after unilateral axotomy of control (H) and mutant (I) animals. The facial motor nucleus (7n) is circumscribed with a dashed line. Note the sharp decrease in motoneurons in Jun^ΔSC animals in the axotomized side (ax). Bar in H (applies also to I), 0.2 mm. Quantification is shown in J. Motoneuron cell count showing a strong decrease in survival 31 d after nerve cut in the absence of SC c-Jun in Jun^ΔSC (n = 6) and their littermate controls (n = 9), same animals as in A–I. (K) Number of αX+ microglial nodules in the axotomized facial motor nucleus per 20-µm-thick section (n = 5 Jun^ΔSC mutants and n = 5 Jun^f/f controls). (L) Regeneration distance (in mm, distal from crush) for the fastest growing CGRP+ and galanin+ motor axons, 4 d after facial nerve crush (n = 4 Jun^ΔSC mutants and n = 4 Jun^f/f controls). (M) Density of αM+ macrophages 4 d after crush, at the facial nerve injury site (0 mm) and 2 and 4 mm distally (n = 4 Jun^ΔSC mutants and n = 4 Jun^f/f controls). (J–M) *, P < 0.05 in Student’s t test.