The beta1D protein is a recently characterized isoform of the integrin @entity11952 subunit that is present in cardiac and skeletal muscles. In this study, we have examined the expression of beta1D in different types of skeletal muscle and in cardiac muscle and studied its distribution during @entity19 development, using new monoclonal antibodies specific for beta1D. Immunoprecipitation studies revealed that, while beta1A is strongly expressed in proliferating C2C12 myoblasts, beta1D is only expressed after their differentiation to myotubes. In these myotubes, beta1D is associated with different alpha subunits, namely alpha3A, alpha5, alpha7A, or alpha7B. Initially, during embryogenesis, the @entity1226 subunit is the only @entity11952 variant expressed in skeletal and cardiac muscle. The beta1D subunit is first detected in skeletal muscle at E17.5, whereas in cardiac muscle its expression begins around the time of birth. Later the expression of beta1A in skeletal and cardiac muscle becomes restricted to capillary cells, whereas beta1D eventually becomes the only variant expressed in adult @entity299 cells. The switch from the beta1A to the beta1D subunit in cardiac muscle cells coincides with the expression of @entity34220 . In adults there is a distinct concentration of beta1D at the myotendinous junctions of muscle fibers and at costameres in both @entity299 . In addition, beta1D is present at intercalated discs in cardiac muscle and at neuromuscular junctions in skeletal muscle cells. The amount of beta1D in different types of skeletal muscle (fast, slow, and mixed-type) was similar, but cardiac muscle expressed almost five times as much of this protein. We suggest that beta1D plays a role in the maintenance of the cytoarchitecture of mature muscle and in the functional integrity of the muscle cells.

Spatial and temporal expression of the beta1D integrin during XXXX development.

@entity19 :: ('10090', 'Species') :: ['mouse'] @entity1226 :: ('12286(Tax:10090)', 'Gene') :: ['alpha1A'] @entity34220 :: ('16404(Tax:10090)', 'Gene') :: ['alpha7'] @entity11952 :: ('15129(Tax:10090)', 'Gene') :: ['beta1'] @entity299 :: ('MESH:D006331', 'Disease') :: ['cardiac and skeletal muscle']
@entity19 :: (10090,Species) :: ['mouse']
