Fig. 1. RT-PCR analysis of somites from HH 10, 12, 15, 17 and 19 embryos, as well as ED6 wing bud, using primers specific for sMyHC1, 2, 3, efast MyHC and nfast MyHC. Total RNA was isolated from the three rostral-most somites of embryos at each stage and subjected to 36 cycles of RT-PCR. The first transcripts to appear are efast MyHC and sMyHC3, followed by sMyHC1 and finally sMyHC2. Transcripts of nfast MyHC were not detected in the somites at these stages, but were easily detected with 36 cycles in the wing bud at ED6.