Fig. 4.

Functional studies of keratin 18 (Krt18)-knockout (KO) and Krt18-dominant-negative (DN) genotypes. A: wild-type (WT), Krt18-KO, and Krt18-DN mice were placed on a treadmill and their ability to run was assayed as the treadmill speed was increased. The bar graph shows the speed (y-axis) at which the mice in that group stopped running. No differences were apparent (ANOVA, with Prism, with Tukey’s post hoc multiple-comparisons test: WT, n = 7; Krt18-KO, n = 4; Krt18-DN, n = 4; results averaged over 3 separate experiments with each cohort). B: tibialis anterior (TA) muscles were analyzed for specific force in vivo by attaching their distal tendons to a force transducer, followed by stimulation via transcutaneous electrodes to the fibula nerve. n = 6 for each group. Krt18-KO and Krt18-DN muscles differed significantly in maximal force compared with WT (P < 0.05) at levels similar to those seen with the Krt19-KO. Muscles lacking desmin (Des KO, double knockout, DKO) showed a larger effect. *P < 0.001; n = 5–6/genotype compared with WT. Statistics determined by ANOVA followed by pairwise multiple comparison (Holm-Sidak), performed on SigmaPlot.