Systematic association mapping identifies NELL1 as a novel IBD disease gene

Area of Science:

• Genetics
• Gastroenterology
• Immunology

Background:

• Crohn disease (CD) is a complex polygenic disorder within inflammatory bowel disease (IBD).
• Existing CD-associated genetic variants explain only a portion of the disease's heritability.
• Identifying novel susceptibility loci is crucial for understanding IBD pathogenesis.

Purpose of the Study:

• To conduct a genome-wide scan to identify novel genetic variants associated with Crohn disease in a German population.
• To validate potential CD susceptibility loci in independent German and international cohorts.
• To investigate the role of identified loci in other forms of inflammatory bowel disease, such as ulcerative colitis (UC).

Main Methods:

• Multi-stage genome-wide scan of 393 German CD cases and 399 controls.
• Testing 116,161 single-nucleotide polymorphisms (SNPs) for association.
• Replication and fine-mapping in independent German, French/Canadian, and UK patient samples, including family-based studies (trios).

Main Results:

• Confirmed associations with known CD loci: NOD2, 5q31 haplotype, and 5p13.1.
• Identified a novel association with NELL1 (rs1793004) in German samples, consistently replicated in independent cohorts.
• NELL1 demonstrated a significant association with IBD across German UC patients (p<10(-6), OR=1.66).
• The 5p13.1 locus was also replicated in French/Canadian and UK CD samples.
• Replicated associations with additional genes: ITGB6, GRM8, OR5V1, PPP3R2, NM_152575, and HNF4G.

Conclusions:

• NELL1 represents a novel, ubiquitous susceptibility locus for inflammatory bowel disease.
• The 5p13.1 locus is a confirmed susceptibility region for Crohn disease.
• These findings expand the understanding of the genetic architecture of IBD and identify new targets for research.