title: The C42R mutation in the Kir6.2 (KCNJ11) gene as a cause of transient neonatal diabetes, childhood diabetes, or later-onset, apparently type 2 diabetes mellitus.
abstract: BACKGROUND
  Known genes in maturity-onset diabetes of the young account for only a fraction of families with dominantly inherited diabetes in Japan. There should be as-yet-unidentified genes that account for the rest of the patients.
  
  
  OBJECTIVE
  To identify and characterize the mutation responsible for a Japanese family with dominantly inherited diabetes mellitus.
  
  
  METHODS
  Members of a four-generation family with dominantly inherited diabetes mellitus observed in three generations. None of the patients in this family had permanent neonatal diabetes. One had transient neonatal diabetes, one had childhood diabetes, and the others had adult-onset diabetes without autoantibodies or insulin resistance.
  
  
  METHODS
  Screening of the chromosomal location of the gene by a genome-wide linkage analysis followed by candidate gene sequencing. Confirmation of the functional significance of the identified mutation by the population survey and the physiological analysis.
  
  
  RESULTS
  We identified a novel mutation (C42R) in the KCNJ11 gene coding for the Kir6.2 subunit of the pancreatic ATP-sensitive potassium channel. The patch-clamp experiments using the mutated KCNJ11 showed that the mutation causes increased spontaneous open probability and reduced ATP sensitivity. The effect, however, was partially compensated by the reduction of functional ATP-sensitive potassium channel expression at the cell surface, which could account for the milder phenotype of our patients.
  
  
  CONCLUSIONS
  These results broaden the spectrum of diabetes phenotypes caused by mutations of KCNJ11 and suggest that mutations in this gene should be taken into consideration for not only permanent neonatal diabetes but also other forms of diabetes with milder phenotypes and later onset.
authors.affiliation: Department of Pediatrics, Kyoto University Hospital, 54 Shogoin Sakyo, Kyoto 606-8507, Japan. yorif@kuhp.kyoto-u.ac.jp
authors.forename: Tohru
authors.initials: T
authors.lastname: Yorifuji
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Nagashima
authors.forename: Keiji
authors.initials: K
authors.lastname: Kurokawa
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kawai
authors.forename: Mariko
authors.initials: M
authors.lastname: Oishi
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Akazawa
authors.forename: Masaya
authors.initials: M
authors.lastname: Hosokawa
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Yamada
authors.forename: Nobuya
authors.initials: N
authors.lastname: Inagaki
authors.forename: Tatsutoshi
authors.initials: T
authors.lastname: Nakahata
mesh_terms: D019943:Amino Acid Substitution; D001483:Base Sequence; D004247:DNA / Q000097:blood / Q000235:genetics / Q000302:isolation & purification; D017931:DNA Primers; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics*; D004553:Electric Conductivity; D005260:Female; D005799:Genes, Dominant; D006801:Humans; D007231:Infant, Newborn; D015640:Ion Channel Gating / Q000502:physiology; D008297:Male; D020125:Mutation, Missense; D010375:Pedigree; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D000099161:Kcnj11 Channel
chemical_list: D004247:DNA; D017931:DNA Primers; D024661:Potassium Channels, Inwardly Rectifying; D000099161:Kcnj11 Channel