title: Mutations in the insulin gene can cause MODY and autoantibody-negative type 1 diabetes.
abstract: OBJECTIVE
  Mutations in the insulin (INS) gene can cause neonatal diabetes. We hypothesized that mutations in INS could also cause maturity-onset diabetes of the young (MODY) and autoantibody-negative type 1 diabetes.
  
  
  METHODS
  We screened INS in 62 probands with MODY, 30 probands with suspected MODY, and 223 subjects from the Norwegian Childhood Diabetes Registry selected on the basis of autoantibody negativity or family history of diabetes.
  
  
  RESULTS
  Among the MODY patients, we identified the INS mutation c.137G>A (R46Q) in a proband, his diabetic father, and a paternal aunt. They were diagnosed with diabetes at 20, 18, and 17 years of age, respectively, and are treated with small doses of insulin or diet only. In type 1 diabetic patients, we found the INS mutation c.163C>T (R55C) in a girl who at 10 years of age presented with ketoacidosis and insulin-dependent, GAD, and insulinoma-associated antigen-2 (IA-2) antibody-negative diabetes. Her mother had a de novo R55C mutation and was diagnosed with ketoacidosis and insulin-dependent diabetes at 13 years of age. Both had residual beta-cell function. The R46Q substitution changes an invariant arginine residue in position B22, which forms a hydrogen bond with the glutamate at A17, stabilizing the insulin molecule. The R55C substitution involves the first of the two arginine residues localized at the site of proteolytic processing between the B-chain and the C-peptide.
  
  
  CONCLUSIONS
  Our findings extend the phenotype of INS mutation carriers and suggest that INS screening is warranted not only in neonatal diabetes, but also in MODY and in selected cases of type 1 diabetes.
authors.affiliation: Gade Institute, University of Bergen, Norway.
authors.forename: Anders
authors.initials: A
authors.lastname: Molven
authors.forename: Monika
authors.initials: M
authors.lastname: Ringdal
authors.forename: Anita M
authors.initials: AM
authors.lastname: Nordbø
authors.forename: Helge
authors.initials: H
authors.lastname: Raeder
authors.forename: Julie
authors.initials: J
authors.lastname: Støy
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Lipkind
authors.forename: Donald F
authors.initials: DF
authors.lastname: Steiner
authors.forename: Louis H
authors.initials: LH
authors.lastname: Philipson
authors.forename: Ines
authors.initials: I
authors.lastname: Bergmann
authors.forename: Dagfinn
authors.initials: D
authors.lastname: Aarskog
authors.forename: Dag E
authors.initials: DE
authors.lastname: Undlien
authors.forename: Geir
authors.initials: G
authors.lastname: Joner
authors.forename: Oddmund
authors.initials: O
authors.lastname: Søvik
authors.forename: Graeme I
authors.initials: GI
authors.lastname: Bell
authors.forename: Pål R
authors.initials: PR
authors.lastname: Njølstad
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology / Q000235:genetics*; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology / Q000235:genetics* / Q000276:immunology*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007328:Insulin / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009664:Norway / Q000453:epidemiology; D010375:Pedigree; D010641:Phenotype; D012042:Registries
chemical_list: D001323:Autoantibodies; D007328:Insulin