Limits...
Association of a functional variant in the Wnt co-receptor LRP6 with early onset ileal Crohn's disease.

Koslowski MJ, Teltschik Z, Beisner J, Schaeffeler E, Wang G, Kübler I, Gersemann M, Cooney R, Jewell D, Reinisch W, Vermeire S, Rutgeerts P, Schwab M, Stange EF, Wehkamp J - PLoS Genet. (2012)

Bottom Line: Different ileal CD-associated genes including NOD2, ATG16L1, and recently the β-catenin-dependant Wnt transcription factor TCF7L2 have been linked to impaired PC antimicrobial function.In addition, we confirmed a direct relationship between LRP6 activity and the transcriptional expression of HD-5 using transient transfection.Impairments in Wnt signalling and Paneth cell biology seem to represent pathophysiological hallmarks in small intestinal inflammation and should therefore be considered as interesting targets for new therapeutic approaches.

View Article: PubMed Central - PubMed

Affiliation: Dr. Margarete-Fischer-Bosch Institute for Clinical Pharmacology and University of Tübingen, Stuttgart, Germany.

ABSTRACT
Ileal Crohn's Disease (CD), a chronic small intestinal inflammatory disorder, is characterized by reduced levels of the antimicrobial peptides DEFA5 (HD-5) and DEFA6 (HD-6). Both of these α-defensins are exclusively produced in Paneth cells (PCs) at small intestinal crypt bases. Different ileal CD-associated genes including NOD2, ATG16L1, and recently the β-catenin-dependant Wnt transcription factor TCF7L2 have been linked to impaired PC antimicrobial function. The Wnt pathway influences gut mucosal homeostasis and PC maturation, besides directly controlling HD-5/6 gene expression. The herein reported candidate gene study focuses on another crucial Wnt factor, the co-receptor low density lipoprotein receptor-related protein 6 (LRP6). We analysed exonic single nucleotide polymorphisms (SNPs) in a large cohort (Oxford: n = 1,893) and prospectively tested 2 additional European sample sets (Leuven: n = 688, Vienna: n = 1,628). We revealed an association of a non-synonymous SNP (rs2302685; Ile1062Val) with early onset ileal CD (OR 1.8; p = 0.00034; for homozygous carriers: OR 4.1; p = 0.00004) and additionally with penetrating ileal CD behaviour (OR 1.3; p = 0.00917). In contrast, it was not linked to adult onset ileal CD, colonic CD, or ulcerative colitis. Since the rare variant is known to impair LRP6 activity, we investigated its role in patient mucosa. Overall, LRP6 mRNA was diminished in patients independently from the genotype. Analysing the mRNA levels of PC product in biopsies from genotyped individuals (15 controls, 32 ileal, and 12 exclusively colonic CD), we found particularly low defensin levels in ileal CD patients who were carrying the variant. In addition, we confirmed a direct relationship between LRP6 activity and the transcriptional expression of HD-5 using transient transfection. Taken together, we identified LRP6 as a new candidate gene in ileal CD. Impairments in Wnt signalling and Paneth cell biology seem to represent pathophysiological hallmarks in small intestinal inflammation and should therefore be considered as interesting targets for new therapeutic approaches.

Show MeSH

Related in: MedlinePlus

Known exonic SNPs in LRP6.(A) LRP6 gene card with locations of exonic SNPs published in the NCBI SNPdb. Variants which lead to an amino acid exchange are marked in red. A deletion mutation causing a different protein chain is marked in blue, silent variants are marked in green. (B) Linkage disequilibria (LD) of the exonic SNPs in CD patients of the Oxford cohort. 7 of the genotyped SNPs were not present. We conclude that there is no significant LD between the sole coding variant (rs2302685) and any of the synonymous SNPs.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3285585&req=5

pgen-1002523-g001: Known exonic SNPs in LRP6.(A) LRP6 gene card with locations of exonic SNPs published in the NCBI SNPdb. Variants which lead to an amino acid exchange are marked in red. A deletion mutation causing a different protein chain is marked in blue, silent variants are marked in green. (B) Linkage disequilibria (LD) of the exonic SNPs in CD patients of the Oxford cohort. 7 of the genotyped SNPs were not present. We conclude that there is no significant LD between the sole coding variant (rs2302685) and any of the synonymous SNPs.

Mentions: We studied frequency distributions and linkage disequilibria of all SNPs reported in the NCBI SNPdatabase in the exonic regions of LRP6 (Figure 1 upper panel). For a first analysis we used a well-defined cohort from Oxford including almost 2000 DNA samples from healthy controls and IBD patients. We determined frequencies for 5 of the 12 exonic SNPs described in the NCBI SNPdb (Figure 1 lower panel). SNPs with a minor allele frequency (MAF) of 0 in the Oxford samples were either not previously validated or so far not been found in western European cohorts. None of the tested SNPs were associated with CD or UC overall. However, in this first analysis, the coding rare allele of rs2302685 exhibited an association with a subgroup: an early disease onset phenotype in ileal CD (odds ratio (OR) 1.524, 95% confidence interval (CI) 0.988 to 2.345, p = 0.05511; for homozygous carriers OR 3.152, 95% CI 1.128 to 8.845, p = 0.02144). Since none of the other analysed SNPs showed frequency differences between controls and the different analysed disease groups we focused only on rs2302685 for additional tests. We also did not find a significant linkage between this variant and any of the other tested polymorphic SNPs and therefore did not include them in the analysis of the two additional cohorts (Figure 1 lower panel).


Association of a functional variant in the Wnt co-receptor LRP6 with early onset ileal Crohn's disease.

Koslowski MJ, Teltschik Z, Beisner J, Schaeffeler E, Wang G, Kübler I, Gersemann M, Cooney R, Jewell D, Reinisch W, Vermeire S, Rutgeerts P, Schwab M, Stange EF, Wehkamp J - PLoS Genet. (2012)

Known exonic SNPs in LRP6.(A) LRP6 gene card with locations of exonic SNPs published in the NCBI SNPdb. Variants which lead to an amino acid exchange are marked in red. A deletion mutation causing a different protein chain is marked in blue, silent variants are marked in green. (B) Linkage disequilibria (LD) of the exonic SNPs in CD patients of the Oxford cohort. 7 of the genotyped SNPs were not present. We conclude that there is no significant LD between the sole coding variant (rs2302685) and any of the synonymous SNPs.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3285585&req=5

pgen-1002523-g001: Known exonic SNPs in LRP6.(A) LRP6 gene card with locations of exonic SNPs published in the NCBI SNPdb. Variants which lead to an amino acid exchange are marked in red. A deletion mutation causing a different protein chain is marked in blue, silent variants are marked in green. (B) Linkage disequilibria (LD) of the exonic SNPs in CD patients of the Oxford cohort. 7 of the genotyped SNPs were not present. We conclude that there is no significant LD between the sole coding variant (rs2302685) and any of the synonymous SNPs.
Mentions: We studied frequency distributions and linkage disequilibria of all SNPs reported in the NCBI SNPdatabase in the exonic regions of LRP6 (Figure 1 upper panel). For a first analysis we used a well-defined cohort from Oxford including almost 2000 DNA samples from healthy controls and IBD patients. We determined frequencies for 5 of the 12 exonic SNPs described in the NCBI SNPdb (Figure 1 lower panel). SNPs with a minor allele frequency (MAF) of 0 in the Oxford samples were either not previously validated or so far not been found in western European cohorts. None of the tested SNPs were associated with CD or UC overall. However, in this first analysis, the coding rare allele of rs2302685 exhibited an association with a subgroup: an early disease onset phenotype in ileal CD (odds ratio (OR) 1.524, 95% confidence interval (CI) 0.988 to 2.345, p = 0.05511; for homozygous carriers OR 3.152, 95% CI 1.128 to 8.845, p = 0.02144). Since none of the other analysed SNPs showed frequency differences between controls and the different analysed disease groups we focused only on rs2302685 for additional tests. We also did not find a significant linkage between this variant and any of the other tested polymorphic SNPs and therefore did not include them in the analysis of the two additional cohorts (Figure 1 lower panel).

Bottom Line: Different ileal CD-associated genes including NOD2, ATG16L1, and recently the β-catenin-dependant Wnt transcription factor TCF7L2 have been linked to impaired PC antimicrobial function.In addition, we confirmed a direct relationship between LRP6 activity and the transcriptional expression of HD-5 using transient transfection.Impairments in Wnt signalling and Paneth cell biology seem to represent pathophysiological hallmarks in small intestinal inflammation and should therefore be considered as interesting targets for new therapeutic approaches.

View Article: PubMed Central - PubMed

Affiliation: Dr. Margarete-Fischer-Bosch Institute for Clinical Pharmacology and University of Tübingen, Stuttgart, Germany.

ABSTRACT
Ileal Crohn's Disease (CD), a chronic small intestinal inflammatory disorder, is characterized by reduced levels of the antimicrobial peptides DEFA5 (HD-5) and DEFA6 (HD-6). Both of these α-defensins are exclusively produced in Paneth cells (PCs) at small intestinal crypt bases. Different ileal CD-associated genes including NOD2, ATG16L1, and recently the β-catenin-dependant Wnt transcription factor TCF7L2 have been linked to impaired PC antimicrobial function. The Wnt pathway influences gut mucosal homeostasis and PC maturation, besides directly controlling HD-5/6 gene expression. The herein reported candidate gene study focuses on another crucial Wnt factor, the co-receptor low density lipoprotein receptor-related protein 6 (LRP6). We analysed exonic single nucleotide polymorphisms (SNPs) in a large cohort (Oxford: n = 1,893) and prospectively tested 2 additional European sample sets (Leuven: n = 688, Vienna: n = 1,628). We revealed an association of a non-synonymous SNP (rs2302685; Ile1062Val) with early onset ileal CD (OR 1.8; p = 0.00034; for homozygous carriers: OR 4.1; p = 0.00004) and additionally with penetrating ileal CD behaviour (OR 1.3; p = 0.00917). In contrast, it was not linked to adult onset ileal CD, colonic CD, or ulcerative colitis. Since the rare variant is known to impair LRP6 activity, we investigated its role in patient mucosa. Overall, LRP6 mRNA was diminished in patients independently from the genotype. Analysing the mRNA levels of PC product in biopsies from genotyped individuals (15 controls, 32 ileal, and 12 exclusively colonic CD), we found particularly low defensin levels in ileal CD patients who were carrying the variant. In addition, we confirmed a direct relationship between LRP6 activity and the transcriptional expression of HD-5 using transient transfection. Taken together, we identified LRP6 as a new candidate gene in ileal CD. Impairments in Wnt signalling and Paneth cell biology seem to represent pathophysiological hallmarks in small intestinal inflammation and should therefore be considered as interesting targets for new therapeutic approaches.

Show MeSH
Related in: MedlinePlus