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High-throughput characterization of functional variants highlights heterogeneity and polygenicity underlying lung cancer susceptibility

ABSTRACT: Genome-wide association studies (GWAS) have identified multiple lung cancer risk loci including those that are distinct in the major histological types. However, most of these loci have not been functionally characterized. Here we employed massively parallel reporter assays (MPRA) to assess allelic transcriptional activity of risk-associated variants en masse. We tested 2,245 variants in 42 loci from 3 recent GWASs of East Asian and European populations in the context of lung adenocarcinoma and squamous cell carcinoma cells while incorporating exposure to a tobacco-smoke carcinogen, benzo[a]pyrene. At FDR < 0.01, we identified 844 MPRA-significant variants with allelic transcriptional activity across 88% of lung cancer loci. Further variant scoring using lung-specific epigenomic annotation demonstrated that 63% of the loci harbored multiple equally functional variants in linkage disequilibrium. Cell-type-specific variants were observed in 72% of the loci, a subset of which aligned with histology-specific association in the GWAS. Distinct subsets of transcription factors were predicted to bind to cell-type-specific variants and those affecting multiple GWAS loci in trans. Linking MPRA-significant variants to target genes based on four different approaches identified candidate susceptibility genes including essential genes for lung cancer cell growth. CRISPR-interference of a high-scoring MPRA-significant variant validated multiple variant-gene connections from different datasets, including RTEL1, SOX18, and ARFRP1. Our data provide a comprehensive catalog of functional characterization of lung cancer GWAS loci and the molecular basis of heterogeneity and polygenicity of lung cancer susceptibility.

ORGANISM(S): Homo sapiens

PROVIDER: GSE245699 | GEO | 2024/05/16

REPOSITORIES: GEO

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Project description:Background: The identification of causal variants responsible for disease associations from genome-wide association studies (GWAS) facilitates functional understanding of the disease mechanisms implicated by GWAS. One of the earliest GWAS associations to COPD spans an intragenic region within FAM13A, but the causal variants at this loci have not yet been identified. Massively parallel reporter assays (MPRA) can be used to prioritize functional regulatory variants in a high-throughput manner. Methods: We used an integrated approach using fine-mapping in over 10,000 subjects from COPD GWAS studies, two MPRA experiments, traditional reporter assays, chromatin conformation capture, and CRISPR-based gene editing to characterize COPD-associated regulatory variants in FAM13A in human bronchial epithelial cell lines. Results: Conditional genetic association and fine mapping analyses identified two independent COPD association signals in FAM13A. MPRA identified 45 common functional regulatory variants, and six COPD-associated putative functional variants were prioritized for further functional investigation. Three variants demonstrated significant activity in traditional reporter assays, and one variant, rs2013701, was selected for further testing in the endogenous genomic context based on a direction of effect consistent with postulated mechanisms of FAM13A-mediated COPD susceptibility. CRISPR-based genome editing for this variant confirmed allele-specific effects on FAM13A expression and altered rates of cellular proliferation, providing multiple levels of functional characterization for this COPD-associated variant. Conclusions: Comprehensive screening for regulatory variants near FAM13A identified the presence of extensive functional regulatory variation within a 250kb window of FAM13A in HBECs. Focused functional evaluation of the COPD-associated functional variants in LD with the two independent association signals in this region prioritized the common variant rs2013701, for which multiple parallel lines of functional evidence confirm allelic effects on FAM13A regulation.

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High-throughput characterization of functional variants highlights heterogeneity and polygenicity underlying lung cancer susceptibility

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