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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.

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Correlation of HD-5 and LRP6.Linear regression and Spearman rank analysis were used on all samples from the mRNA analysis. The samples were grouped according to A) their disease state (diseased mucosa or non-inflamed mucosa of patients) as well as in all samples B) according to the LRP6 genotype. Interestingly the two factors exhibit a correlating pattern in controls (independent of the genotype) as well as in all wild type samples but not in the C-allele carrying individuals.
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pgen-1002523-g004: Correlation of HD-5 and LRP6.Linear regression and Spearman rank analysis were used on all samples from the mRNA analysis. The samples were grouped according to A) their disease state (diseased mucosa or non-inflamed mucosa of patients) as well as in all samples B) according to the LRP6 genotype. Interestingly the two factors exhibit a correlating pattern in controls (independent of the genotype) as well as in all wild type samples but not in the C-allele carrying individuals.

Mentions: Studying the transcriptional expression level of LRP6 in our cohort mucosal biopsy samples, we found generally diminished LRP6 mRNA levels in ileal CD (Figure 3B). As expected, according to the known effect on signalling impairment -but not expression level- [30] the reduction of LRP6 was independent from the functional mutation. The reduced transcriptional expression of LRP6 might be an additional factor which contributes to the especially low levels seen in LRP6 mutated ileal CD patients. Consistent with the latter interpretation, levels of LRP6 showed a significant correlation with the Paneth cell antimicrobial HD-5 in healthy controls (Figure 4A). When analysing all samples according to the genotype we found a significant correlation in all LRP6 wild type individuals (Figure 4B). Interestingly, in carriers of the rare mutant allele (Figure 4B) the correlation was absent supporting a possible direct effect of rs2302685. Similar to HD-5 (Figure 4A), inflammation per se did not seem to affect LRP6 in our sample set, clearly it did not account for the described reduction (Figure 4B). Taken together the data suggest that both, the mutation, as well as the diminished expression level of LRP6 contribute to the reduced levels of HD-5 in ileal CD patients.


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)

Correlation of HD-5 and LRP6.Linear regression and Spearman rank analysis were used on all samples from the mRNA analysis. The samples were grouped according to A) their disease state (diseased mucosa or non-inflamed mucosa of patients) as well as in all samples B) according to the LRP6 genotype. Interestingly the two factors exhibit a correlating pattern in controls (independent of the genotype) as well as in all wild type samples but not in the C-allele carrying individuals.
© Copyright Policy
Related In: Results  -  Collection

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

pgen-1002523-g004: Correlation of HD-5 and LRP6.Linear regression and Spearman rank analysis were used on all samples from the mRNA analysis. The samples were grouped according to A) their disease state (diseased mucosa or non-inflamed mucosa of patients) as well as in all samples B) according to the LRP6 genotype. Interestingly the two factors exhibit a correlating pattern in controls (independent of the genotype) as well as in all wild type samples but not in the C-allele carrying individuals.
Mentions: Studying the transcriptional expression level of LRP6 in our cohort mucosal biopsy samples, we found generally diminished LRP6 mRNA levels in ileal CD (Figure 3B). As expected, according to the known effect on signalling impairment -but not expression level- [30] the reduction of LRP6 was independent from the functional mutation. The reduced transcriptional expression of LRP6 might be an additional factor which contributes to the especially low levels seen in LRP6 mutated ileal CD patients. Consistent with the latter interpretation, levels of LRP6 showed a significant correlation with the Paneth cell antimicrobial HD-5 in healthy controls (Figure 4A). When analysing all samples according to the genotype we found a significant correlation in all LRP6 wild type individuals (Figure 4B). Interestingly, in carriers of the rare mutant allele (Figure 4B) the correlation was absent supporting a possible direct effect of rs2302685. Similar to HD-5 (Figure 4A), inflammation per se did not seem to affect LRP6 in our sample set, clearly it did not account for the described reduction (Figure 4B). Taken together the data suggest that both, the mutation, as well as the diminished expression level of LRP6 contribute to the reduced levels of HD-5 in ileal CD patients.

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