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Deleted in malignant brain tumors 1 (DMBT1) is a secreted glycoprotein displaying a broad bacterial-binding spectrum. Recent functional and genetic studies linked DMBT1 to the suppression of LPS-induced TLR4-mediated NF-jB activation and to the pathogenesis of Crohn's disease. Here, we aimed at unraveling the molecular basis of its function in mucosal protection and of its broad pathogen-binding specificity. We report that DMBT1 directly interacts with dextran sulfate sodium (DSS) and carrageenan, a structurally similar sulfated polysaccharide, which is used as a texturizer and thickener in human dietary products. However, binding of DMBT1 does not reduce the cytotoxic effects of these agents to intestinal epithelial cells in vitro. DSS and carrageenan compete for DMBT1-mediated bacterial aggregation via interaction with its bacterial-recognition motif. Competition and ELISA studies identify poly-sulfated and poly-phosphorylated structures as ligands for this recognition motif, such as heparansulfate, LPS, and lipoteichoic acid. Dose-response studies in Dmbt1 À/À and Dmbt1 1/1 mice utilizing the DSS-induced colitis model demonstrate a differential response only to low but not to high DSS doses. We propose that DMBT1 functions as pattern-recognition molecule for poly-sulfated and polyphosphorylated ligands providing a molecular basis for its broad bacterial-binding specificity and its inhibitory effects on LPS-induced TLR4-mediated NF-jB activation. IntroductionCrohn's disease (CD) is one of the major subtypes of inflammatory bowel disease (IBD) and is thought to emerge through the complex interplay of various environmental and genetic factors. Nutritional compounds, bacterial pathogens, and the endogenous bacterial microflora have been considered as environmental factors contributing to the etiology of CD [1,2]. The putative involvement of bacteria is also reflected at the level of susceptibility genes for CD, of which some appear to exert important functions in innate mucosal immunity [1,3,4]. Genetic variants of the gene nucleotide-binding oligomerization domain 2/Caspase recruitment domain 15 (NOD2/CARD15) at the IBD1 locus, for example, have been shown to be associated with an increased risk for CD [5][6][7]. NOD2 encodes an intracellular pattern-recognition receptor with specificity for muramyldipeptide, and is thought to function in the sensing of intracellular bacteria [8]. Dysfunction of NOD2 may result in altered NF-kB signaling and attenuated expression of secreted anti-bacterial factors such as a-defensin-2 [9-11]. In addition, decreased copy numbers of the b-defensin-4 gene DEFB4 (HBD-2) at chromosome 8p23.1 have been reported to result in reduced DEFB4 expression levels and to confer an increased risk for CD [4].Recent studies demonstrated that deleted in malignant brain tumors 1 (DMBT1) is up-regulated in the inflamed mucosa of CD patients with normal NOD2 but not in those with the frequent CD-associated L1007fsinsC mutation in NOD2 [12,13]. The DMBT1 gene locates at human chromosome 10q26.13 and ...

Saethre-Chotzen syndrome, a common autosomal dominant craniosynostosis in humans, is characterized by brachydactyly, soft tissue syndactyly and facial dysmorphism including ptosis, facial asymmetry, and prominent ear crura. Previously, we identified a yeast artificial chromosome that encompassed the breakpoint of an apparently balanced t(6;7) (q16.2;p15.3) translocation associated with a mild form of Saethre-Chotzen syndrome. We now describe, at the DNA sequence level, the region on chromosome 7 affected by this translocation event. The rearrangement occurred approximately 5 kb 3' of the human TWIST locus and deleted 518 bp of chromosome 7. The TWIST gene codes for a transcription factor containing a basic helix-loop-helix (b-HLH) motif and has recently been described as a candidate gene for Saethre-Chotzen syndrome, based on the detection of mutations within the coding region. Potential exon sequences flanking the chromosome 7 translocation breakpoint did not hit known genes in database searches. The chromosome rearrangement downstream of TWIST is compatible with the notion that this is a Saethre-Chotzen syndrome gene and implies loss of function of one allele by a positional effect as a possible mechanism of mutation to evoke the syndrome.