HaploReg v4 defines a core set of 52 054 804 variants, consisting primarily of single-nucleotide polymorphisms (SNPs) using all refSNP IDs, hg19 positions and alleles from dbSNP release b137 (12). Corresponding hg38 coordinates for these variants were obtained from dbSNP release b141. This core set of dbSNP variants was integrated with other data sets either by rsID (for GWAS, eQTL and 1000 Genomes data) or by intersecting intervals by coordinate using the BEDTools software package (13) (for all other functional tracks.)
