Comparison of Notch signals transmitted to C2C12 myoblasts from OP9-Jagged1 and OP9-Delta1. (A) Differentiation of C2C12 myoblast cells after 7 days coculture on OP9-MigR1, OP9-Jagged1, or OP9-Delta1 in the presence of carrier alone (0.1% DMSO) or increasing concentrations of γ-secretase inhibitor X. (B) RT-PCR analysis for expression of a myotube differentiation marker, MLC2, in C2C12 myoblasts shown in panel A. Total RNA extracted from a single well was reverse transcribed and normalized by TaqMan PCR for HPRT.