Similarly, five causal genes of muscle-relevant diseases, including MSTN and DLK1 of muscular hypertrophy, TNNT1 of muscular dystrophy, CLCN1 of myotonia, and PYGM of glycogen storage disease, exhibited a strong muscle-specific expression, but showed different expression patterns as development progressed (Figure 7G). The gene discussed is PYGM; the disease is disorder of glycogen metabolism.