SLC6A14 and intestinal obstruction in the newborn due to guanylate cyclase 2C deficiency: The associated modifier loci colocalized with expression quantitative trait loci (eQTLs) for ATP12A (p = 3.35x10-8), SLC6A14 (p = 1.12x10-10) and SLC26A9 (p = 4.48x10-5) in the pancreas, even though meconium ileus manifests in the intestine.