MIP4IBD: An Easy and Rapid Genotyping-by-Sequencing Assay for the Inflammatory Bowel Diseases Risk Loci

Inflammatory bowel diseases (IBD) are polygenic, with many genetic variants contributing to disease risk. Knowing the genotype of specific variants or calculating a combined genetic risk score benefits translational and functional research. To address this, we developed MIP4IBD, a flexible and cost-effective genotyping-by-sequencing assay using molecular inversion probes (MIPs).

The assay targets 463 IBD risk variants, and 77 additional relevant variants. Molecular inversion probes capture and library preparation were optimized using 15 IBD DNA samples, comparing genotypes with immunochip. A custom GitHub pipeline was created for data processing, performance testing, and genotype calling. The final design was validated on a larger scale (149 IBD patients, 104 non-IBD controls, and 3 external cell lines), incorporating post hoc quality control criteria.

The assay achieved a 3.5-day turnaround time at €15 per sample with optimal sample throughput, demonstrating a 92.6% success rate in variant capture and genotype concordance rates of 99.3% and 99.6% with Infinium Global Screening Array24 BeadChip and WGS, respectively. A downstream application involved the calculation of a weighted IBD polygenic risk score (PRS), which was significantly higher in IBD patients than controls (mean 0.42 vs -0.49, P = 1.95E-11). Individuals in the highest PRS quartile had a 15.7-fold (95% CI: 6.5-38.3) risk of developing IBD and an earlier age of onset (26 vs 37 years, P = 0.02), compared to the lowest quartile.

MIP4IBD is a validated, scalable genotyping assay targeting IBD risk loci, with an integrated bioinformatics pipeline from sequencing data to genotypes and PRS calculation. Its cost-effectiveness and flexibility for additional variants make it particularly appealing for translational and clinical applications.