Astrocyte dystroglycan complexes in brain development

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DESCRIPTION (Applicant's abstract): The dystrophin-glycoprotein complex (DGC) is a well characterized array of cytoplasmic, membrane spanning, and extracellular matrix proteins that form a critical linkage between the cytoskeleton and the basal lamina of striated muscle. Within the central nervous system (CNS), similar dystroglycan linkages to basal laminae are present at two interfaces formed by astrocytes: (1) foot processes abutting on cerebral blood vessels and (2) foot processes that form the glia limitans at the pial surface of the brain. The former interface is critical for formation and maintenance of the blood-brain barrier, while the latter is likely to play important roles in anchoring radial glia during neuronal migration. Basal lamina abnormalities at the glia limitans have been identified in some forms of congenital muscular dystrophy in humans (e.g. Fukuyama muscular dystrophy) and basal lamina disruption at the glia limitans leads to abnormal CNS development in animal models. In this proposal, we will focus attention on the central protein in the astrocyte-basal lamina linkage, dystroglycan. Our Specific Aims propose to identify protein elements of the astrocyte-dystroglycan complex, elucidate protein interactions within the complex, and demonstrate the importance of the astrocyte dystroglycan complex during CNS development. Through the use of Cre-lox methodology, we plan to create a novel murine model of CNS developmental disorders. This project is a cross-discipline collaboration among investigators with expertise in clinical neuropathology and in basic neuroscience, molecular biology, cell biology, and membrane physiology who are uniquely situated to carry out the proposed studies. Aim 1: To define the composition of the astrocyte-dystroglycan complex(es), we will test the hypothesis that one-or-more dystroglycan complexes are present in astrocytes using a combination of biochemical and immunohistochemical methods. These studies will utilize tissue sections and cultured astrocytes from wild type mice and mice with naturally occurring or genetically engineered mutations of one or more of the DGC components known to be expressed in astrocytes. Aim 2: To create a new model of CNS developmental abnormalities by selectively disrupting the astrocyte-dystroglycan complex. Dystroglycan +/-, dystroglycan lox/lox, and GFAP-Cre mice will be bred to produce GFAP-Cre/dystroglycan lox/- and GFAP-Cre/dystroglycan lox/lox mice. This strategy should disrupt the astrocyte DGC beginning in the latter half of embryonic development. We believe this strategy will produce mice with neuronal migration and cerebrovascular defects.