Figure 3. Differential protection of tibialis anterior (TA) and soleus (SO) muscles after denervation in MuRF1-KO mice.

A, B) Comparison of whole muscle mass 14 days after denervation (DEN). TA muscles were strongly protected from atrophy in a MuRF1-KO background and only lost 6% mass during 14 days of denervation. SO atrophied in both WT and MuRF1-KO mice; atrophy protection in the MuRF1-KO mice was 13% when compared to WT. a: p<0.05 vs WT control group; b: p<0.05 vs MuRF1 KO control group and c: p<0.05 vs WT denervated group.

C) Consistent with the total muscle mass protection of TA, single fiber cross sectional areas (CSA) from MuRF1-KO mice remained strongly protected after DEN. Elevated CSAs before DEN contributed to this effect. a: p<0.05 vs WT control group; b: p<0.05 vs MuRF1 KO control group and c: p<0.05 vs WT denervated group.

D) Fiber type composition in SO and its dependence on DEN and MuRF1 expression. Black bars represent type I, white bars type II and grey bars intermediate fiber type occurrence as percentile of total fibers. DEN resulted in the prominent appearance of an intermediate fiber type in the MuRF1-KO background (also detectable in WT after DEN at low frequency). a: p<0.05 vs WT control group; b: p<0.05 vs MuRF1 KO control group and c: p<0.05 vs WT denervated group.

Error bars represent the mean of at least 3 measurements from 3 independent experiments, lines represent standard deviation.