Evaluation of the colocalization of uromodulin with the ER luminal marker protein PDI, whose abundance was not altered in presence of ADTKD–SEC61A1 mutations (Fig 1), revealed an aberrant maturation of uromodulin only in cells with the Sec61α–V67G mutation (Fig 4A). Here, P4HB is linked to autosomal dominant medullary cystic kidney disease with or without hyperuricemia.