Accumulation of muscle-specific RNA sequences during myogenesis

DNA complementary to rat skeletal muscle polyadenylated RNA was enriched for sequences specific for terminal differentiation by hybridization to RNA extracted from cloned mononucleated myogenic cells and subsequent removal of the hybridized cDNA. The remaining cDNA (musclespecific cDNA) was hybridized to RNA extracted from primary skeletal muscle cultures harvested at short time intervals during differentiation. The experiments indicate that sequences specific for terminal differentiation accumulate close to the time of cell fusion, possibly a few hours prior to it. DNA complementary to polyadenylated muscle RNA was fractionated by hybridization to its template at a low R₀t and separation of the hybridized (abundant) and nonhybridized (rare) cDNA. Hybridization of these fractions to RNA extracted from cultures harvested prior to or after cell fusion showed that the abundant cDNA is very much enriched for sequences specific for terminal differentiation.