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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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HD-6 but not lysozyme is reduced in patients who carry the rare LRP6 variant.Linear regression and Spearman rank analysis were used on all samples from the mRNA analysis according to the LRP6 genotype. (A) The two Paneth cell α-defensins correlate in both subgroups fitting the also found genotype dependent decrease of HD-6 in ileal CD patients. This, as well as the independence from inflammation matches the pattern seen for HD-5. (B) Lysozyme on the other hand does not correlate with HD-5 and seems to be uninfluenced by the LRP6 genotype in ileal CD.
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pgen-1002523-g005: HD-6 but not lysozyme is reduced in patients who carry the rare LRP6 variant.Linear regression and Spearman rank analysis were used on all samples from the mRNA analysis according to the LRP6 genotype. (A) The two Paneth cell α-defensins correlate in both subgroups fitting the also found genotype dependent decrease of HD-6 in ileal CD patients. This, as well as the independence from inflammation matches the pattern seen for HD-5. (B) Lysozyme on the other hand does not correlate with HD-5 and seems to be uninfluenced by the LRP6 genotype in ileal CD.

Mentions: Since HD-6, the second most abundant Paneth cell product is also reduced in ileal CD, we additionally analysed its expression according to the LRP6 genotype in our patients. It is known that both Paneth cell α-defensins are regulated by the Wnt pathway, so we expected a similar effect. As hypothesized, the two factors showed a correlating pattern in wild type as well as in mutated individuals in our cohort and HD-6 exhibited the same dependence on the LRP6 genotype which was seen for HD-5 in ileal CD (Figure 5A). We also measured lysozyme, another antimicrobial found in Paneth cells which is not decreased in ileal CD and also not known to be dependent on canonical Wnt. As expected, there was no change in lysozyme mRNA levels in ileal CD carriers of the rare LRP6 SNP compared to the wild type ileal CD subgroup and also no correlation with HD-5 in either subgroup.


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)

HD-6 but not lysozyme is reduced in patients who carry the rare LRP6 variant.Linear regression and Spearman rank analysis were used on all samples from the mRNA analysis according to the LRP6 genotype. (A) The two Paneth cell α-defensins correlate in both subgroups fitting the also found genotype dependent decrease of HD-6 in ileal CD patients. This, as well as the independence from inflammation matches the pattern seen for HD-5. (B) Lysozyme on the other hand does not correlate with HD-5 and seems to be uninfluenced by the LRP6 genotype in ileal CD.
© Copyright Policy
Related In: Results  -  Collection

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

pgen-1002523-g005: HD-6 but not lysozyme is reduced in patients who carry the rare LRP6 variant.Linear regression and Spearman rank analysis were used on all samples from the mRNA analysis according to the LRP6 genotype. (A) The two Paneth cell α-defensins correlate in both subgroups fitting the also found genotype dependent decrease of HD-6 in ileal CD patients. This, as well as the independence from inflammation matches the pattern seen for HD-5. (B) Lysozyme on the other hand does not correlate with HD-5 and seems to be uninfluenced by the LRP6 genotype in ileal CD.
Mentions: Since HD-6, the second most abundant Paneth cell product is also reduced in ileal CD, we additionally analysed its expression according to the LRP6 genotype in our patients. It is known that both Paneth cell α-defensins are regulated by the Wnt pathway, so we expected a similar effect. As hypothesized, the two factors showed a correlating pattern in wild type as well as in mutated individuals in our cohort and HD-6 exhibited the same dependence on the LRP6 genotype which was seen for HD-5 in ileal CD (Figure 5A). We also measured lysozyme, another antimicrobial found in Paneth cells which is not decreased in ileal CD and also not known to be dependent on canonical Wnt. As expected, there was no change in lysozyme mRNA levels in ileal CD carriers of the rare LRP6 SNP compared to the wild type ileal CD subgroup and also no correlation with HD-5 in either subgroup.

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