Dystroglycan contributes to the formation of multiple dystrophin-like complexes in brain

In muscle, dystrophin anchors a complex of proteins at the cell surface which includes alpha-dystroglycan, beta-dystroglycan, syntrophins and dystrobrevins. Mutations in the dystrophin gene lead to muscular dystrophy and mental retardation. In contrast to muscle, little is known about the localization and the molecular interactions of dystrophin and dystrophin associated proteins (DAPs) in brain. In the present study, we show that alpha-dystroglycan and dystrophin are localized to large neurones in cerebral cortex, hippocampus, cerebellum and spinal cord. Furthermore, we show that dystroglycan is a member of three distinct dystrophin-containing complexes. Two of these complexes contain syntrophin and both dystrophin and syntrophin are enriched in post-synaptic densities. These data suggest that dystrophin and DAPs may have a role in the organization of CNS synapses. Interestingly, the enrichment for syntrophin in post-synaptic densities is not affected in mice mutant for all dystrophin isoforms. Thus in the brain, unlike in muscle, the association of syntrophin with dystrophin is not crucial for the DAP complex which suggests that it may be associated with other proteins.