Mouse skeletal muscle C2C12 cells were initially plated on 15 cm plates in DMEM with 20% fetal bovine serum. At confluence, the cells were switched to low serum medium to initiate myogenic differentiation. For extraction of total RNA, cells were first rinsed in PBS and then lysed in Trizol reagent (Invitrogen catalog # 15596-026) either during exponential growth in high serum medium, or at 60 hrs, 5 days and 7 days after medium shift. Residual contaminating genomic DNA was removed from the total RNA fraction using Turbo DNA-free (Ambion catalog # AM1907M). mRNA was isolated from DNA-free total RNA using the Dynabeads mRNA Purification Kit (Invitrogen catalog # 610-06).