The most prominent differences were seen for MYH4 (specific for fast twitch type IIB fibers), which was 4-fold more abundant in 3-month-old vs. 2-day-old WT pigs, whereas in DMD pigs no significant age-related increase was observed, resulting in a markedly reduced MYH4 level in 3-month-old DMD vs. WT muscle. The gene discussed is MYH4; the disease is Duchenne muscular dystrophy.