MUC1 and autosomal dominant medullary cystic kidney disease with or without hyperuricemia: Additional studies focused on MUC1 (a gene responsible for medullary cystic kidney disease (MCKD) type 1) reveal that renal expression of alternatively spliced mRNA isoform of MUC1 may be the key biological mechanism behind the genetic association signal captured in previous GWAS of CKD-dt.