Expression of dystrophin-associated protein 35DAG (A4) and 50DAG (A2) is confined to striated muscles

A monoclonal antibody MA4-2 against a dystrophin-associated protein 35DAG (A4) was established and applied to examine the distribution of 35DAG in monkey tissue and its expression in DMD patients. In immunoblotting after two-dimensional gel electrophoresis of crude skeletal muscle extracts, MA4-2 reacted exclusively with an apparent single spot located in a similar position to rabbit 35DAG in each animal examined. 35DAG was detected only in striated muscles (quadriceps femoris and cardiac muscles), but not in other tissues examined, including smooth muscle (aorta, uterus), brain, nerve, lung, and liver. This distribution pattern is the same as that of 50DAG but different from that of 43DAG (A3a) [Mizuno et al. (1993) J. Biochem. 114, 936-941]. In Duchenne muscular dystrophy muscles, 35DAG was distinctly present, but greatly reduced in amount. This is also the case with 50DAG. On the basis of these results, it is concluded that 35DAG and 50DAG are striated muscle-specific and may be important in the pathogenesis of Duchenne muscular dystrophy.