Figure 5.

MAP kinase signaling is altered in ΔICR/ΔICR myoblasts and myotubes. (A and B) Comparison of gene expression changes that occur during myoblast differentiation in wild type and in ΔICR/ΔICR cells. We used RNA sequencing to identify genes where expression changed by >2-fold (FDR < 0.01) after 24 h in differentiation medium. (A) Venn diagram shows that more than 75% (1713 out of 2268) genes changed during normal myoblast differentiation are misregulated in LOI cells. (B) Top five pathways altered in wild type, but not ΔICR/ΔICR cells, during differentiation. Cell cycle and DNA replication pathways are highly over-represented among these genes. (C and D) Direct comparison of wild type and LOI cells at each developmental stage. (C) Selected pathways enriched in genes differentially expressed in LOI cells compared to wild type at the myoblast and myotube stages. Cell cycle, p53 signaling and the upstream MAP kinase signaling pathways are affected in both myoblast and myotube cells. (D) Heatmap of genes in the MAP kinase signaling pathway that are differentially expressed in LOI vs. wild type cells at the myoblast or myotube stage. Differentially expressed genes in this pathway show the same effect of the LOI mutation in both cell types, indicating early developmental defects.