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

Genetic variation in the 6p22.3 gene DTNBP1, the human ortholog of the mouse dysbindin gene, is associated with schizophrenia

Prior evidence has supported the existence of multiple susceptibility genes for schizophrenia. Multipoint linkage analysis of the 270 Irish high-density pedigrees that we have studied, as well as results from several other samples, suggest that at least one such gene is located in region 6p24-21. In the present study, family-based association analysis of 36 simple sequence-length-polymorphism markers and of 17 SNP markers implicated two regions, separated by approximately 7 Mb. The first region, and the focus of this report, is 6p22.3. In this region, single-nucleotide polymorphisms within the 140-kb gene DTNBP1 (dystrobrevin-binding protein 1, or dysbindin) are strongly associated with schizophrenia. Uncorrected, empirical P values produced by the program TRANSMIT were significant (P<.01) for a number of individual SNP markers, and most remained significant when the data were restricted to include only one affected offspring per nuclear family per extended pedigree; multiple three-marker haplotypes were highly significant (P=.008-.0001) under the restricted conditions. The pattern of linkage disequilibrium is consistent with the presence of more than one susceptibility allele, but this important issue is unresolved. The number of markers tested in the adjacent genes, all of which are negative, is not sufficient to rule out the possibility that the dysbindin gene is not the actual susceptibility gene, but this possibility appears to be very unlikely. We conclude that further investigation of dysbindin is warranted.

Dystroglycan is selectively associated with inhibitory GABAergic synapses but is dispensable for their differentiation

The dystrophin glycoprotein complex (DGC) is a multimolecular complex that links the extracellular matrix to the cytoskeleton. The DGC is present at the skeletal neuromuscular junction and required for its maturation and maintenance. Members of the DGC are also expressed in brain. We used cultured hippocampal neurons to analyze the distribution, regulation, and role in synaptogenesis of the major transmembrane component of the DGC, dystroglycan; one of its extracellular ligands, agrin; and one of its cytoskeletal binding partners, dystrophin. alpha-Dystroglycan, beta-dystroglycan, and dystrophin clustered at a subset of inhibitory synapses containing GABA(A)R subunits alpha1, alpha2, and gamma2, and the inhibitory receptor anchoring protein gephyrin. DGC components were not detected at excitatory glutamatergic synapses. Dystroglycan is the first identified adhesive macromolecule at mature GABA synapses. Developmentally, dystroglycan clustered at synaptic loci after synaptic vesicles, GABA(A)R, and gephyrin, the latter being closely associated with GABA(A)R at all stages of synaptogenesis analyzed. Analysis of gephyrin -/-, agrin -/-, and mdx mouse hippocampal neurons in culture indicated that synaptic clustering of dystroglycan occurs independently of gephyrin, agrin, and dystrophin. In dystroglycan-deficient neurons, cultured from a conditional mutant strain, GABAergic synapses differentiated with clusters of gephyrin and GABA(A)R apposed to synaptic terminals, but these synapses did not contain detectable dystrophin. Thus the DGC is not essential for GABAergic synaptogenesis but is likely to function in modulating inhibitory synapses or conferring specialized properties on a subset of them.

Targeted transduction patterns in the mouse brain by lentivirus vectors pseudotyped with VSV, Ebola, Mokola, LCMV, or MuLV envelope proteins

Lentiviral vectors have proven to be promising tools for transduction of central nervous system (CNS) cells in vivo and in vitro. In this study, CNS transduction patterns of lentiviral vectors pseudotyped with envelope glycoproteins from Ebola virus, murine leukemia virus (MuLV), lymphocytic choriomeningitis virus (LCMV), or the rabies-related Mokola virus were compared to a vector pseudotyped with the vesicular stomatitis virus glycoprotein (VSV-G). Mokola-, LCMV-, and VSV-G-pseudotyped vectors transduced similar populations, including striatum, thalamus, and white matter. Mokola-pseudotyped vectors were the most efficient of the three. MuLV-pseudotyped lentivirus efficiently transduced striatum and hippocampal dentate gyrus. In contrast, no transduction resulted from injection of Ebola-pseudotyped virus in the CNS. The same pattern was observed in vitro with primary cultured oligodendrocytes. LCMV, MuLV, and Ebola pseudotypes were the most stable. These results demonstrate that targeted transduction in the CNS can be achieved using specific envelope glycoproteins to pseudotype lentiviral vectors, and support the use of Mokola-pseudotyped and MuLV-pseudotyped lentiviral vectors as efficient and stable alternatives to VSV-G-pseudotyped vectors for experiments in the mouse CNS.