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Chunk #66 — Methods — Within- and cross-ancestry fine mapping

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Multi-ancestry study of the genetics of problematic alcohol use in over 1 million individuals.
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removed one from the analysis. The second is cross-ancestry fine mapping for the 100 regions with independent variants identified in cross-ancestry meta-analyses. For each region, we performed clumping (within 500 kb and LD r2 > 0.1) in EUR, AFR and LA summary data for the lead SNP separately, to select three sets of SNPs (P < 0.05) for fine mapping, with corresponding LD reference panels from the 1000 Genomes Project. For each set of SNPs, we calculated the pair-wise LD and randomly removed one SNP if r2 = 1. If the lead SNP was not presented in the EUR SNP set, we did not perform fine mapping for this region. Loci with limited numbers of variants cannot have convergent results, so they are not included in the results. After that, this cross-ancestry analysis included 92 regions. For the ten regions in which the lead SNPs are missing in both AFR and LA populations, we did within-ancestry fine mapping in EUR instead to keep the lead SNP (cross-ancestry fine mapping will only analyze the SNPs common in analyzed ancestries). Next, because the credible set length identified is related to the number of variants in the input, to provide a more direct