Dsk3 and Dsk4 pigmentary phenotype. (a,b) Whole footpads and tails (a) or separated tail epidermis and dermis (b) from adult animals. (c) Skin darkness (mean ± s.e.m.) of epidermis and dermis for each genotype. (d) Histological sections of footpad epidermis show pigment accumulation in the epidermis (arrow). (e–h) Xgal-stained adult footpad epidermis (e, inset), whole footpad (f) and E15.5 embryos (h) from +/+ and Dsk4/+ animals that also carry the Dct-lacZ transgene. A dashed circle denotes the area without Xgal-positive cells. (g) Number of Xgal-positive cells (mean ± s.e.m.) from the location shown in e (inset). For c and g, P values for mutant versus control (based on a two-tail t-test) are 1.53 × 10–5 and 0.0036 (c), and 0.0017 and 0.0036 (g), for Dsk3/+ and Dsk4/+, respectively. Scale bars: b, 500 μm; d,f, 50 μm; e,h, 300 μm.