Fig. 8 Impaired apoptotic response of K1014chim skin in response to UV-B irradiation. The back skin of newborn K1014chim mutants (Mut; n=5) and wild-type littermates (WT; n=4) was irradiated with 100 mJ/cm2 UV-B. 24 hours later, the skin was isolated and processed for (a) TUNEL and (b) BrdU staining. The number of TUNEL- and BrdU-positive keratinocytes in the interfollicular epidermis was determined (the average value for the wild-type samples was defined as 100%). Note that K1014 skin showed a 27% decrease in TUNEL-positive cells compared with wild-type control skin (Mut: 57±4, WT: 78±11; P<0.05). The proliferation indices of mutant and wild-type samples were essentially the same (Mut: 26±5; WT: 25±5). Error bars show standard deviation.