Disrupted differentiation of C2C12 cells by Igf2 KD. (A) Relative expression levels of Cav3, Csrp3, and Myoz1 in Igf2 KD cells. (B) Relative expression levels of Igf2 and muscle genes during differentiation of C2C12 cells. The cells were transduced with empty vector (Emp Vec), Per1, Per2, CBE (Clock, Bmal1, and empty vector), CBP1 (Clock, Bmal1, and Per1), and CBP2 (Clock, Bmal1, and Per2) before differentiation. Igf2 KD cells and control cells were compared. (C and D) Differentiation index (C) and fusion index (D) of the cells used in B. Data are presented as mean + SEM of biological triplicates. Each replicate includes n = 1,000–1,500 nuclei in C and D. *, P < 0.05; **, P < 0.01; and ***, P < 0.001 with Student’s t test compared with control KD cells in A and with empty vector cells in B–D.