The molecular basis of the Kidd blood group polymorphism and its lack of association with type 1 diabetes susceptibility

The Kidd blood group locus encodes a urea transporter which is expressed onhuman red cells and in the kidney. This gene is located on chromosome18q12, and evidence for linkage and association with type 1 diabetesmellitus has been reported. To investigate this further, the genetic basisfor the blood group Jk(a)/Jk(b) polymorphism was first determined bysequencing reverse-transcribed reticulocyte RNAs from Jk(a+b-) and Jk(a-b+)donors. The Jk(a)/Jk(b) polymorphism was caused by a transition (G838A),resulting in a Asp280Asn amino acid substitution and an MnlI restrictionfragment length polymorphism (RFLP). Using the MnlI RFLP, we found that theJk(a)/Jk(b) polymorphism was not in linkage disequilibrium with type 1diabetes in 228 multiplex UK and US families tested.