Linkage of the human inducible nitric oxide synthase gene to type 1 diabetes

Exposure of human pancreatic islets to a mixture of cytokines induces expre ssion of the inducible nitric oxide synthase (iNOS), impairs p-cell functio n, and induces apoptosis. We performed a mutational scanning of all 27 exon s of the human NOS2 gene and linkage transmission disequilibrium testing of identified NOS2 polymorphisms in a Danish nationwide type 1 diabetes melli tus (IDDM) family collection. Mutational screening was performed using PCR- amplified exons, followed by single stranded conformation polymorphism and verification of potential polymorphisms by sequencing. The transmission dis equilibrium test was performed in an IDDM family material comprising 257 Da nish families; 154 families were affected sibling pair families, and 103 fa milies were simplex families. In total, 10 polymorphisms mere identified in 8 exons, of which 4 were tested in the family material. A C/T single nucle otide polymorphism in exon 16 resulting in an amino acid substitution, Ser( 608)Leu, showed linkage to IDDM in human leukocyte antigen DR3/4-positive a ffected offspring (P = 0.008; corrected P = 0.024). No other distorted tran smission patterns were found for any other tested single nucleotide polymor phism or constructed haplotypes with the exception of those including data from exon 16. In conclusion, linkage of the human NOS2 gene to IDDM in a su bset of patients supports a pathogenic role of nitric oxide in human IDDM.