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DOP36 Family-specific host genetic and gut microbial signatures have a beneficial role in early identification of familial inflammatory bowel diseases

G.Y. SHIN1, Y.M. Park1, E. Ha2, K.N. Gu2, K. Kim2, C.K. Lee1, H.J. Kim1

1Department of Gastroenterology, Center for Crohn’s and Colitis, Kyung Hee University College of Medicine, Seoul, Korea Republic of, 2Department of Biology, Kyung Hee University College of Sciences, Seoul, Korea Republic of

Background

Familial IBD may have its own signatures with respect to host genetic variants and/or gut microbiome. However, available data focussing on this topic is still limited, particularly for Asian patients with familial IBD. We aimed to investigate the possible host genetic and gut microbial signatures in familial IBD through a combined analysis of genomic and metagenomic profiles.

Methods

All patients were affiliated with a prospectively recruited cohort of patients with IBD (NCT03589183) and met the diagnostic criteria of Crohn’s disease (CD) or ulcerative colitis (UC). We constructed a unique family cohort comprising ≥2 affected individuals with familial IBD and ≥1 their unaffected, healthy first-degree relative (FDR) in each family. Whole-exome sequencing for rare variants followed by a genome-wide single-nucleotide polymorphism analysis for common variants was performed. A polygenic risk score (PRS) was calculated separately in Crohn’s disease (CD), ulcerative colitis (UC) or IBD. Gut microbial community was analysed by 16s rRNA sequencing of stool samples.

Results

Eight Korean families comprising 16 with familial IBD (12 concordant IBD, 4 discordant IBD) and 9 FDRs were included for analysis. Whole-exome sequencing identified four family-specific candidate genes (LAMA5, MYO15B, TTN, and WDR66) with rare missense variants that were transmitted preferentially to the affected FDRs in at least ≥3 families (Figure 1). An in silico analysis identified the deleterious effect of the identified variants on the gene products including LAMA5 (SIFT = 0, PolyPhen-2 = 0.72). The patients with CD, but not those with UC, had a significantly higher mean PRS than controls (PRS = 2.137 vs. 0.742, p-value = 0.030). Metagenomic sequencing revealed significant differences in α- and β-diversity of gut microbiota among the patients with CD, those with UC, and unaffected FDRs (all p < 0.05), showing lower microbial richness in the patients with familial IBD (p = 0.02). In various taxonomic levels, compared with unaffected FDRs, the patients with familial IBD showed the significantly differential abundance of several gut bacteria (all corrected p < 0.05; Figure 2).

Conclusion

Family-specific host genetic and gut microbial signatures have a beneficial role in early-identification of familial IBD (NCT03515070).

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