Deletion of brain dystroglycan recapitulates aspects of congenital muscular dystrophy

Fukuyama congenital muscular dystrophy (FCMD), muscle-eye-brain disease (MEB), and Walker-Warburg syndrome are congenital muscular dystrophies (CMDs) with associated developmental brain defects. Mutations reported in genes of FCMD and MEB patients suggest that the genes may be involved in protein glycosylation. Dystroglycan is a highly glycosylated component of the muscle dystrophin-glycoprotein complex that is also expressed in brain, where its function is unknown. Here we show that brain-selective deletion of dystroglycan in mice is sufficient to cause CMD-like brain malformations, including disarray of cerebral cortical layering, fusion of cerebral hemispheres and cerebellar folia, and aberrant migration of granule cells. Dystroglycan-null brain loses its high-affinity binding to the extracellular matrix protein laminin, and shows discontinuities in the pial surface basal lamina (glia limitans) that probably underlie the neuronal migration errors. Furthermore, mutant mice have severely blunted hippocampal long-term potentiation with electrophysiologic characterization indicating that dystroglycan might have a postsynaptic role in learning and memory. Our data strongly support the hypothesis that defects in dystroglycan are central to the pathogenesis of structural and functional brain abnormalities seen in CMD.     

Isolation and partial sequence of recombinant plasmids containing human alpha-, beta- and gamma-globin cDNA fragments.

Human globin cDNA-derived recombinants with plasmid pCR1 have been prepared for use as specific hybridisation probes and for the partial sequencing of alpha-, beta- and gamma-globin genes.     

The role of heteroduplex correction in gene conversion in Saccharomyces cerevisiae

Two different models have been proposed to explain the relative frequencies of the non-mendelian allelic segregations which are detected by tetrad analysis after meiosis in fungi. The first model maintains that 6:2 type tetrads result from correction of heteroduplexes containing mismatched sites and 5:3 type tetrads result from failure to correct mismatched sites. The second model suggests that 6:2 segregations result from the filling-in of double-strand gaps using information obtained from both strands of a homologous duplex. In this model 5:3 type tetrads result if the allele is included in the heteroduplex regions flanking the gap and the resulting mismatched nucleotides are not corrected. We have studied the correction of heteroduplex plasmid DNA in pms1 mutant strains of Saccharomyces cerevisiae, which are known to exhibit higher frequencies of 5:3 type tetrads and lower frequencies of 6:2 tetrads than wild-type strains. Our results suggest that the pms1 mutation causes a defect in mismatch correction, supporting the hypothesis that meiotic gene conversion in wild-type yeast cells often results from the correction of heteroduplex DNA.     

Cellulose synthesis: mutational analysis and genomic perspectives using Arabidopsis thaliana

Cellulose microfibrils containing crystalline β-1,4-glucan provide the major structural framework in higher-plant cell walls. Genetic analyses of Arabidopsis thaliana now link specific genes to plant cellulose production just as was achieved some years earlier with bacteria. Cellulose-deficient mutants have defects in several members of one family within a complex glycosyltransferase superfamily and in one member of a small family of membrane-bound endo-1,4-β-glucanases. The mutants also accumulate a readily extractable β-1,4-glucan that has short chains which, in at least one case, are lipid linked. Cellulose could be made by direct extension of the glucan chain by the glycosyltransferase or, as the mutant suggests, by an indirect route which makes lipid-linked oligosaccharides. Models discussed incorporate the known enzymes and lipo-glucan and raise the possibility that different CesA glycosyltransferases may catalyse different steps. Received 5 January 2001; received after revision 25 April 2001; accepted 25 April 2001     

Collaborative genome-wide association analysis supports a role for ANK3 and CACNA1C in bipolar disorder

To identify susceptibility loci for bipolar disorder, we tested 1.8 million variants in 4,387 cases and 6,209 controls and identified a region of strong association (rs10994336, P = 9.1 x 10(-9)) in ANK3 (ankyrin G). We also found further support for the previously reported CACNA1C (alpha 1C subunit of the L-type voltage-gated calcium channel; combined P = 7.0 x 10(-8), rs1006737). Our results suggest that ion channelopathies may be involved in the pathogenesis of bipolar disorder.