Fig. 5. Immunohistochemistry analysis of dystrophin expression in muscles of utrophin-transgenic mdx mice. (A) Immunohistochemistry with anti-utrophin and anti-dystrophin antibodies in mdx mice and transgenic mdx mice expressing full-length utrophin (utro/mdx) at 1 year of age (note that a proportion of fibers are centrally nucleated in the muscle of mice of the same age that are transgenic for full-length utrophin). Only a single RF is seen in the transgenic mouse compared with a large cluster in the control mdx mouse. (B) The number of RFs in mdx mice (black columns), mdx mice expressing mini-utrophin (gray columns) and mdx mice expressing full-length utrophin (white columns), at 1 month, 6 months and 1 year of age. Each point is the mean ± s.e.m. of 3-8 muscles per group. *Significant difference (P<0.05) from mdx muscles of the same age. Bar, 100 µm.