Representative members of the core dystrophin-glycoprotein complex were identified by mass spectrometry, i.e., dystrophin (DMD), α/β-dystroglycan (DAG1), α-sarcoglycan (SGCA), β-sarcoglycan (SGCB), α-dystrobrevin (DTNA) and α1-syntrophin (SNTA1), and shown to be greatly reduced in both young and aged mdx-4cv diaphragm (Figure 3). Here, DAG1 is linked to Duchenne muscular dystrophy.