Fig. 1.

Hyperpigmentation in C57BL/6 adult mice after nerve injury. A–D, Gross photographs of mice hindlimb areas 1 month after nerve transection and/or deflection. Skin has been removed. A, Wild-type mouse with nerve cut shows little pigmentation (arrows). B,Nf1+/− mouse with nerve cut shows slightly more pigmentation compared with A. C, Wild-type mouse with nerve transection and deflection of the nerve shows some pigmentation. D, Nf1+/− mouse with nerve transection and deflection shows dramatic clusters of highly pigmented cells (arrowheads). E, Toluidine blue-stained plastic section of skin from the lesion area of an Nf1+/− mouse 3 months after nerve cut. Clusters of pigmented cells present in the facia underneath the hypodermis are within the black box. Scale bar, 100 μm. This area was evaluated at the EM level and is shown in F, showing cytoplasmic pigment granules characteristic of a melanocyte (magnification, 2700×). G, Gross photograph of a ventral view of mutant mouse skin over lesioned area 1 month after nerve transection showing pigmentation (arrows).H, In a mutant mouse 1 month after nerve transection, spots of pigmentation extended ventral to the sciatic nerve (arrows).