15 - Genetic and Functional Genomic Data Implicate Monocytes/Macrophages in the Pathobiology of Scleroderma/Systemic Sclerosis

Poster Number: 15
Publication Number: 15.110

Elizabeth A. Crinzi, Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo, BUFFALO, NY, United States; Emma K. Haley, Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo, Buffalo, NY, United States; James N. Jarvis, Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo, Buffalo, NY, United States

Background: Scleroderma/systemic sclerosis (SSc) refers to a spectrum of multisystem connective tissue disorders. While the peak age of onset is between the ages of 20 and 50 years, pediatric cases are well documented, and early-onset disease is associated with a worse prognosis. Genetic variants on non-HLA SSc risk haplotypes contribute to the risk of developing SSc. We recently showed significant enrichment for enhancer associated histone marks in 11 non-HLA SSc risk haplotypes. Since that time, another 27 risk haplotypes for SSc have been identified.

Objective: We surveyed the chromatin architecture in SSc risk haplotypes to gain new insight into how genetic variation may influence disease risk and pathobiology.

Design/Methods: We queried publicly available H3K27ac/H3K4me1 ChIP-seq data in CD14+ monocytes to determine whether the 27 SSc risk haplotypes show enrichment for epigenetic markers of enhancer function. We also queried existing monocyte/macrophage GROseq data, which provides a functional readout of active enhancers. Finally, we analyzed THP-1 cell data using publicly available HiC data to define topologically associated domains (TADs) associated with monocyte enhancers. We refined this process by referring to human monocyte CTCF ChIPseq data and rejecting any putative TAD that was not anchored at each end by CTCF. We undertook ontological analysis of the genes within each TAD to gain insight into the functionality of target genes of enhancers within the TADs that encompass the SSc risk haplotypes.

Results: Of the 27 SSc risk haplotypes we investigated, 20 were significantly enriched (p < 0.001) for both H3K4me1 and H3K27ac markers, and four others were significantly enriched for H34me1 alone. In resting monocytes, 12 were significantly enriched for GROseq peaks (p < 0.01), and within these twelve haplotypes there were forty six H3K27ac peaks. Using HiC data supplemented by CTCF ChIPseq data, we identified 248 genes expressed in monocytes and lying within the TADs that encompass the SSc haplotypes .Conclusion(s): The analysis of twenty-seven non-HLA SSc risk haplotypes reveals significant enrichment for enhancer associated histone markers H3K4me1/H3K27ac and GROseq peaks in CD14+ monocytes. We identified 248 genes that are likely to be influenced by monocyte/macrophage enhancers on these haplotypes.