Figure 6. Utrophin expression was reduced on the extrasynaptic sarcolemma of dko fast 2b fibers.

A) Utrophin expression in transverse sections of the near pure population of fast 2b fibers in the most superficial region of the gastrocnemius muscles. Shown are single sections from mdx^4cv or dko gastrocnemius fast 2b fibers labeled with utrophin in red, α2-laminin in magenta, DAPI in cyan and fast 2b fibers in green. B) Quantitation of maximal extrasynaptic utrophin fluorescence intensity in fast 2b fibers and C) the proportion of fast 2b fibers expressing extrasynaptic utrophin in the mdx^4cv and dko. All bars represent the mean +/− S.D. from n = 4 mice. ^# P<0.05 and ^### P<0.001 compared with mdx^4cv fibers. D) Regenerating fibers expressed utrophin in the mdx^4cv fibers, but not in the dko. Shown are single sections from mdx^4cv or dko superficial gastrocnemius muscles labeled with utrophin in red, developmental myosin heavy chain in green, α2-laminin in yellow and DAPI in cyan. Note that utrophin is on the expanding sarcolemma in mdx^4cv muscles, but not in the dko (arrows). Scale bars  = 50 µm.