Evidence for a susceptibility locus on chromosome 6q influencing phonological coding dyslexia.

A linkage study of 96 dyslexia families containing at least two affected siblings (totaling 877 individuals) has found evidence for a dyslexia susceptibility gene on chromosome 6q11.2-q12 (assigned the name DYX4). Using a qualitative phonological coding dyslexia (PCD) phenotype (affected, unaffected, or uncertain diagnoses), two-point parametric analyses found highly suggestive evidence for linkage between PCD and markers D6S254, D6S965, D6S280, and D6S251 (LOD(max) scores = 2.4 to 2.8) across an 11 cM region. Multipoint parametric analysis supported linkage of PCD to this region (peak HLOD = 1.6), as did multipoint nonparametric linkage analysis (P = 0.012). Quantitative trait linkage analyses of four reading measures (phonological awareness, phonological coding, spelling, and rapid automatized naming speed) also provided evidence for a dyslexia susceptibility locus on chromosome 6q. Using a variance-component approach, analysis of phonological coding and spelling measures resulted in peak LOD scores at D6S965 of 2.1 and 3.3, respectively, under 2 degrees of freedom. Furthermore, multipoint nonparametric quantitative trait sibpair analyses suggested linkage between the 6q region and phonological awareness, phonological coding, and spelling (P = 0.018, 0.017, 0.0005, respectively, for unweighted sibpairs < 18 years of age). Although conventional significance thresholds were not reached in the linkage analyses, the chromosome 6q11.2-q12 region clearly warrants investigation in other dyslexia family samples to attempt replication and confirmation of a dyslexia susceptibility gene in this region.

Context-dependent Pax-5 repression of a PU.1/NF-kappaB regulated reporter gene in B lineage cells.

Enhancers located in the 3' end of the locus in part regulate immunoglobulin heavy chain (IgH) gene expression. One of these enhancers, HS 1,2, is developmentally regulated by DNA binding proteins like NF-kappaB, Pax-5 and the protein complex NF-alphaP in B lineage cells. Here we report that NF-alphaP is the ets protein PU.1. A glutathione-S-transferase (GST)-pulldown assay demonstrated that PU.1 can physically interact with NF-kappaB in solution. Experiments in COS cells showed that PU.1 and NF-kappaB (p50/c-Rel) can activate transcription of an enhancer linked reporter gene. The paired domain protein Pax-5 has previously been shown to repress enhancer-dependent transcription. Additional co-transfection experiments revealed that PU.1/NF-kappaB dependent transcription could be repressed in a context dependent manner by Pax-5, but not by the paired domain of Pax-5. When the PU.1 binding site was substituted with a binding site for the ets-protein Elf-1, Pax-5 could no longer repress reporter gene activity. Our data indicate a model where Pax-5 mediated repression of the HS 1,2 enhancer requires the recruitment of a co-factor which is dependent on Pax-5/PU.1 but which cannot be recruited by Pax-5/Elf-1.

Novel Salmonella typhimurium properties in host--parasite interactions.

Inflammatory bowel disease (IBD) comprises different diseases in the gastrointestinal tract in human, of which Crohn's disease (CD) and ulcerative colitis (UC) are the most prominent. A key factor in the etiology of IBD is the chronic inflammatory process, and a large body of evidence suggests that the transcription factor nuclear factor-kappa B (NF-kappaB) is the key regulator of responses determining the clinical inflammatory condition. Recent findings using antisense oligonucleotides provide direct evidence that the p65 subunit of NF-kappaB plays a central role in chronic intestinal inflammation. It has previously been shown that the Gram negative bacteria Yersinia pseudotubercolosis targets the eukaryotic signal transduction pathway(s) that lead to NF-kappaB activation (and thus avoid an anti-bacterial inflammatory response). In this paper, growth-based selected Salmonella typhimurium clones have been used to generate a clearer picture of the molecular mechanisms involved in host-parasite interactions. From the results presented here, S. typhimurium and Y. pseudotubercolosis may use the same mechanism to block NF-kappaB activation, following host cell infection. A new adaptational feature could also be shown, where a growth-based selected bacteria avoided the normally induced translocation of NF-kappaB in host cells.

Suppression of tumorigenicity in Ras-transformed fibroblasts by alpha 2(I) collagen.

Transformed fibroblasts exhibit reduced adhesion to substrata, a characteristic attributable in part to reduced expression/increased degradation of extracellular matrix (EM) proteins such as type I collagen. To directly assess the role of EM proteins in cellular transformation, a vKRas-transformed mouse fibroblast cell line was transfected with an alpha 2(I) collagen expression construct. Stable transfectants displaying a partial restoration of type I collagen expression showed a flatter morphology with increased adherence to the substratum. These clones also exhibited a reduced ability to clone in soft agar, slower growth kinetics, and suppression of tumorigenicity in nude mice. Restoration of type I collagen is correlated with down-regulation of ras oncogene-responsive NVL3 VL30 gene expression. These results suggest that in addition to suppressing tumorigenicity by promoting cellular adhesion and cytoskeletal organization, EM proteins such as type I collagen may also act to subvert oncoprotein signaling pathways associated with the malignant phenotype.

Analysis of retrotransposon families in genomic DNA by two-dimensional restriction mapping: detection of VL30 insertions in mouse thymic lymphoma.

Reinsertion of mammalian retrotransposable genetic elements is known to be causally associated with tumourigenesis, typically through mechanisms involving insertional deregulation of cellular protooncogene expression. We report here on the application of a two-dimensional restriction mapping-Southern hybridisation approach for analysis of retrotransposon families of low to moderate genetic complexity, which is particularly suited to pairwise comparisons between DNA samples. By using this method, non-constitutional mink-cell-focus-forming type retro-elements were readily detectable in AKR mouse thymic lymphomas against a background of approx. 30 related elements in control DNA. However, in the WEHI 3B myeloid leukaemia cell line, the resolution of two-dimensional mapping permitted detection of only occasional reinsertions of intracisternal A particle retro-elements (genetic complexity: 10(3)). In analysing the VL30 family of retrotransposon (genetic complexity: 150) we developed a strategy for identifying the known transcriptionally active sub-set of these elements in genomic DNA through the generation of an internal, diagnostic restriction fragment. Moreover, in some cases of thymic lymphoma, several candidate re-insertions of VL30 elements were detected, consistent with a suggested role for retrotransposition of this class of element in lymphomagenesis of retroviral aetiology.