Human sample analyses

Frozen colon tissue and formalin‐fixed paraffin‐embedded (FFPE) samples from adult normal, Crohn's disease, and ulcerative colitis patients were obtained from the Cooperative Human Tissue Network (CHTN) via the University of Pennsylvania Center for Molecular Studies in Digestive and Liver Diseases Molecular Biology and Gene Expression Core. Patient demographics are listed in Table 1. RNA was extracted from frozen tissue using Trizol (Thermo Fisher, Waltham, MA). Publicly available RNA‐sequencing data from the RISK cohort of pediatric ileal Crohn's 38 were evaluated for differential expression of IGF2BP1 (IMP1), IMP2, and IMP3. Sequenced reads were trimmed using Trim Galore! (version 0.4.4), and aligned to the GRCh37 reference genome using STAR, version 2.5.3a. Uniquely mapped reads were quantified by Ensembl gene IDs using featureCounts from Subread version 1.6.0. Lowly or unexpressed genes were removed from the analysis if they showed < 2 counts per million in < 5 samples across all conditions. Read counts were transformed with voom and evaluated for differential expression using limma. Immunohistochemistry for IMP1 in human tissue sections was performed using anti‐IMP1 (Santa Cruz, sc‐21026, Table EV4) using Animal‐Free Blocker (Vector Laboratories).