The chromosome X (SLC6A14; panel (a) of Fig 2) and chromosome 1 (SLC26A9; panel (b) of Fig 2) loci were identified as genome-wide significant in an earlier meconium ileus study by the GMC [12] using a subset of the current study sample (S3 Table); this earlier study also demonstrated that a set of 157 genes that code for constituents of the apical plasma membrane where CFTR resides (see Supplementary Table 3 in [12]) were significantly enriched for variants associated with meconium ileus, and this gene-set association was replicated in the French Gene Modifier Study (FGMS) cohort [12, 32]. Here, SLC6A14 is linked to Meconium ileus.