Identification of Novel Gene Mutations and Interactions That Determine Paneth Cell Granule Phenotype in Crohn's Disease
Ta-Chiang Liu, Kelli L VanDussen, Robi D Mitra, Rich Head, Elizabeth A Montgomery, Thaddeus S Stappenbeck. Johns Hopkins U, Baltimore; Washington U., St. Louis
Background: Previous studies have identified >90 susceptibility genes for Crohn's disease (CD). We have shown that combination of ATG16L1 hypomorphism and persistent norovirus infection results in CD-like pathology in mouse models through altering Paneth cell (PC) granule phenotypes. However, little is known about the biologic implications of these abnormal granules and whether other susceptible genes have similar impact. The aims of this study are to investigate if abnormal PC phenotypes were associated with changes in ileal gene expression, and to correlate susceptibility genotype and PC phenotype in CD patients.
Design: Adult CD patients who underwent ileocolectomy between 2005 - 2010 with available genotype and tissue material were enrolled. H&E sections of uninvolved ileum were selected for lysozyme immunofluorescent stains and corresponding tissue blocks were used for microarray and RNA-Seq to assess gene transcription. PC were categorized based on previously described lysozyme stain patterns. Peripheral blood was collected and genotyped by Illumina HumanOmni1-Quad BeadChip. PC phenotypes were then correlated with genotype results.
Results: Seventy-seven patients who met the criteria were enrolled. Unsupervised hierarchal clustering of the microarray data set segregated the CD patients into 2 major clusters; ∼6000 genes were differentially expressed between these clusters, including those involved in autophagy and viral sensing. Patients with an abnormal PC phenotype tended to associate with one cluster vs. the other. In addition, the presence of 1 or 2 NOD2 risk alleles was associated with an increased proportion of abnormal granules (p<0.05). PTPN2 mutation alone showed significantly reduced normal granules and when presented with NOD2 mutation, showed further increased abnormal granules (p<0.05). Mutations of MUC19, TNFSF15 and IBD-5 showed increased abnormal granules exclusively in the presence of NOD2 mutation, whereas mutations of IL-12B and C13orf31 showed increased abnormal granules exclusively in patients with wildtype NOD2.
Conclusions: Abnormal PC phenotype correlates with more global changes in gene expression in CD. NOD2 is a major determinant in PC phenotype and shows similar but distinct changes from that associated with ATG16L1 risk allele. MUC19, PTPN2, TNFSF15, and IBD-5 mutations result in additive/synergistic effects in conjunction with NOD2 mutation. Mutations of IL-12B and C13orf31 show altered PC phenotype exclusively in NOD2 wildtype background. These data provide valuable implication in interaction of these genes.
Tuesday, March 20, 2012 11:00 AM
Platform Session: Section D, Tuesday Morning