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Steven R Brant

Publications and source records attributed to Steven R Brant.

24 records · Page 2Linked to original sources
PubMed2003

MDR1 Ala893 polymorphism is associated with inflammatory bowel disease.

Crohn disease (CD) and ulcerative colitis (UC) are overlapping chronic inflammatory bowel diseases (IBDs). Suggestive evidence for linkage at chromosome 7q has been reported for both CD and UC. Contained within this region is the gene for MDR1 (multidrug resistance), a membrane transport protein for which human polymorphisms have been reported in Ala893Ser/Thr and C3435T that alter pharmacokinetic profiles for a variety of drugs. Because mdr1 knockout mice spontaneously develop colitis, exonic regions were resequenced and tested for IBD association in a large, multicenter North American cohort. Two missense mutations, Asn21Asp and Ala893Ser/Thr, as well as the expression-associated polymorphism C3435T, described elsewhere, were genotyped in the entire cohort. Significant association of Ala893 with IBD was observed by both case-control analysis (P=.002) and the pedigree disequilibrium test (PDT [P=.00020-.00030]) but not for the Asn21Asp or C3435T polymorphisms. Significant association by PDT was observed within the subset with CD (P=.0014-.00090), with similar, nonsignificant trends in a smaller subset with UC. The Ala893Ser/Thr variant is triallelic, and the associated, common allele is Ala893, with undertransmission of the 893Ser (common) and the 893Thr (rare) variants. The Ala893 variant has decreased activity compared with the 893Ser variant; therefore, the association with human IBD is consistent with the murine model of mdr1 deficiency. Taken together, these data support the association of the common Ala893 polymorphism with IBD specifically and, more broadly, provides additional support for its contribution to interindividual pharmacogenetic variation.

Alanine↗
PubMed2003

Crohn's disease-associated NOD2 variants share a signaling defect in response to lipopolysaccharide and peptidoglycan.

BACKGROUND & AIMS: The NOD2 variants R702W, G908R, and L1007fsinsC are strongly associated with Crohn's disease (CD) in both European and American populations, but whether this susceptibility extends to all ethnic groups remains unknown. Except for the L1007fsinsC mutation, which produces a truncated NOD2 protein, the functional activity of the major CD-associated variants G908R and R702W is unknown. METHODS: Individuals were genotyped for R702W, G908R, and L1007fsinsC. The ability of G908R, R702W, and L1007fsinsC variants in the presence and absence of P268S to confer responsiveness to lipopolysaccharide (LPS) and peptidoglycan (PGN) was determined in HEK293T kidney cells. RESULTS: G908R and L1007fsinsC, but not R702W, were associated with disease susceptibility in Ashkenazi Jews. Ashkenazi Jews with CD had significantly higher allele frequency carriage of G908R and lower carriage of R702W compared with non-Jewish whites with CD. Functional studies revealed that the G908R, R702W, and L1007fsinsC variants in the presence and absence of P268S are defective in their ability to respond to bacterial LPS and PGN, whereas P268S alone exhibited wild-type activity. CONCLUSIONS: R702W is not associated with susceptibility to CD in Ashkenazi Jews. The G908R, R702W, and L1007fsinsC variants share a common signaling defect in response to bacterial components, providing evidence for a unifying molecular mechanism whereby NOD2 mutations contribute to disease susceptibility.

Alleles↗
PubMed2003

Defining complex contributions of NOD2/CARD15 gene mutations, age at onset, and tobacco use on Crohn's disease phenotypes.

BACKGROUND: Multiple factors, particularly IBD family history, tobacco use, age at diagnosis and recently, NOD2 mutant genotypes may influence Crohn's disease (CD) heterogeneity. METHODS: We performed a multicenter retrospective record analysis of 275 unrelated patients with CD. Age at diagnosis, IBD family history, Jewish ethnicity, tobacco use at diagnosis, surgical history, disease site and clinical behavior were correlated with genotypes for NOD2 mutations, and all risk factors were assessed for independent influence on outcomes of disease site, behavior and surgery free survival. RESULTS: Risk of ileal disease was increased for CD patients with two NOD2 mutations (Odds Ratio, O.R. 10.1), a smoking history (O.R. 2.25 per pack per day at diagnosis) or a younger age at diagnosis (O.R. 0.97 per each increased year). Presence of ileal disease (O.R. 4.8) and carrying one or two NOD2 mutations (O.R. 1.9 and 3.5, respectively) were independent risk factors for stricturing or non-perianal fistulizing behavior. Ileal disease, youthful onset and smoking at diagnosis (but not NOD2 mutations) were risk factors for early surgery. CONCLUSIONS: Carrying two NOD2 mutations predicts youthful onset, ileal disease involvement, and development of stricturing or non-perianal fistulizing complications. Smoking and early onset independently influence ileal site and time to surgery.

Adult↗
PubMed2002

Evidence for an inflammatory bowel disease locus on chromosome 3p26: linkage, transmission/disequilibrium and partitioning of linkage.

Crohn's disease and ulcerative colitis, the two major forms of idiopathic inflammatory bowel disease (IBD), are heritable, complex traits that appear to share some but not all susceptibility loci. We report that transmission/disequilibrium test analysis of a Crohn's disease genome scan dataset has detected an inflammatory bowel disease locus on chromosome 3p26 (nominal P=0.000052 and genome-wide corrected P=0.039 at D3S1297). An allele sharing method shows significant linkage (multipoint lod=3.69) in a larger, independent sample of inflammatory bowel disease-affected sibling pairs. A survey of 16 chromosome 3p26 short tandem repeat polymorphisms in a combined sample of 234 independent nuclear families with 324 IBD-affected sibling pairs shows significant linkage to chromosome 3p26 (multipoint lod=3.78) and significant transmission/disequilibrium test results at two adjacent markers (nominal P values in two different transmission/disequilibrium analysis methods=0.00011 and 0.0011 for the first marker, and 0.00071 and 0.00013 for the second marker). There is highly significant under-transmission of a common allele and modest over-transmission of other alleles at both markers. Families with no transmission to affected individuals of the under-transmitted alleles show significant linkage (multipoint lod=4.50) that is significantly greater in four simulation studies (P=0.0001, 0.0000625, 0.0000625 and 0.0000625, respectively) than the linkage evidence in families with transmission of the under-transmitted alleles (multipoint lod=0.12). Thus, the existence of an inflammatory bowel disease locus on chromosome 3p26 is supported by significant linkage, transmission/disequilibrium and partitioning of linkage evidence.

Chromosome Mapping↗
PubMed2002

Genetics of inflammatory bowel disease.

The etiology of inflammatory bowel diseases, Crohn's disease and ulcerative colitis, is uncertain. Studies of specific environmental factors and immune dysfunction have provided limited insight into disease pathogenesis. There is ample evidence that these diseases are in part the result of genetic predisposition. The early search for candidate genes focused on genes involved in the regulation of immune function. Recent genome-wide searches reported several susceptibility loci for Crohn's disease and ulcerative colitis. The recent identification of the IBD1 gene (NOD2) with mutations that are associated with susceptibility to Crohn's disease will have a major impact on the understanding of the genetics of this disease.

Australia↗