Sarcoidosis is characterized by a hyperimmune response resulting in granuloma formation in multiple organs. It affects African Americans (AAs) more frequently and more severely than whites. While previous linkage, admixture, candidate gene and genome-wide association (GWA) studies show statistically compelling effects, causal variants are still unknown and much of sarcoidosis heritability is yet to be explained. This "missing" heritability likely includes effects of both common (minor allele frequency (MAF)>5%) and rare variants (MAF<5%), since, in AAs, the former are inadequately represented and the latter are completely unexplored by commercial genotyping arrays. These facts, coupled with the availability of next-generation sequencing compel us to perform an exhaustive search for genetic variants that form the basis of sarcoidosis. For this proposal, we will integrate massivel parallel human exome and targeted sequencing data with previously collected genotype and phenotype data in AA sarcoidosis families to identify undiscovered genetic variants. Our extensive, one-of-a-kind sample will maximize power to detect RV association and help to establish phase, which is critical in understanding the molecular physiology of variants. We will 1) identify coding region variants by exome sequencing, 2) capture variants in the coding and noncoding sequence of 39 regions identified by previous studies via targeted resequencing, and 3) replicate, in an independent sample, true positive CV and RV effects. Our assembled team has led the search for sarcoidosis genes in AAs, and with expertise in pulmonology, genetics, epidemiology, genome sequencing, biostatistics and bioinformatics, we are the only group in the world perfectly poised to successfully complete the proposed projects. The data generated are certain to identify candidate causal variants, provide fundamental insight for functional studies and lead to important new hypotheses of inflammation resulting in new treatments in not only sarcoidosis but other inflammatory diseases as well.
Sarcoidosis is a debilitating disease that affects African Americans (AAs) far more frequently and severely than US whites. Identifying common and rare causal variants and characterizing their role in AA sarcoidosis susceptibility will bridge a significant gap in our understanding of sarcoidosis genetics and provide insight into etiology and pathology.
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|Levin, Albert M; Iannuzzi, Michael C; Montgomery, Courtney G et al. (2014) Admixture fine-mapping in African Americans implicates XAF1 as a possible sarcoidosis risk gene. PLoS One 9:e92646|
|Levin, Albert M; Adrianto, Indra; Datta, Indrani et al. (2014) Performance of HLA allele prediction methods in African Americans for class II genes HLA-DRB1, -DQB1, and -DPB1. BMC Genet 15:72|