title: Monoallelic ABCC8 mutations are a common cause of diazoxide-unresponsive diffuse form of congenital hyperinsulinism.
abstract: ABCC8 encodes a subunit of the β-cell potassium channel (KATP ) whose loss of function is responsible for congenital hyperinsulinism (CHI). Patients with two recessive mutations of ABCC8 typically have severe diffuse forms of CHI unresponsive to diazoxide. Some dominant ABCC8 mutations are responsible for a subset of diffuse diazoxide-unresponsive forms of CHI. We report the analysis of 21 different ABCC8 mutations identified in 25 probands with diazoxide-unresponsive diffuse CHI and carrying a single mutation in ABCC8. Nine missense ABCC8 mutations were subjected to in vitro expression studies testing traffic efficiency and responses of mutant channels to activation by MgADP and diazoxide. Eight of the 9 missense mutations exhibited normal trafficking. Seven of the 8 mutants reaching the plasma membrane had dramatically reduced response to MgADP or to diazoxide (<10% of wild-type response). In our cohort, dominant KATP mutations account for 22% of the children with diffuse unresponsive-diazoxide CHI. Their clinical phenotype being indistinguishable from that of children with focal CHI and diffuse CHI forms due to two recessive KATP mutations, we show that functional testing is essential to make the most reliable diagnosis and offer appropriate genetic counseling.
authors.affiliation: Department of Genetics, AP-HP Groupe Hospitalier Pitié-Salpétrière, Université Pierre et Marie Curie, Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Saint-Martin
authors.forename: Q
authors.initials: Q
authors.lastname: Zhou
authors.forename: G M
authors.initials: GM
authors.lastname: Martin
authors.forename: C
authors.initials: C
authors.lastname: Vaury
authors.forename: G
authors.initials: G
authors.lastname: Leroy
authors.forename: J-B
authors.initials: JB
authors.lastname: Arnoux
authors.forename: P
authors.initials: P
authors.lastname: de Lonlay
authors.forename: S-L
authors.initials: SL
authors.lastname: Shyng
authors.forename: C
authors.initials: C
authors.lastname: Bellanné-Chantelot
mesh_terms: D000483:Alleles; D019943:Amino Acid Substitution; D044903:Congenital Hyperinsulinism / Q000175:diagnosis / Q000188:drug therapy* / Q000235:genetics*; D004252:DNA Mutational Analysis; D003981:Diazoxide / Q000627:therapeutic use*; D004351:Drug Resistance / Q000235:genetics*; D005260:Female; D005808:Genes, Recessive; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009154:Mutation; D010641:Phenotype; D064233:Sulfonylurea Receptors / Q000235:genetics* / Q000378:metabolism; D016896:Treatment Outcome
chemical_list: C577507:ABCC8 protein, human; D064233:Sulfonylurea Receptors; D003981:Diazoxide
keywords: ABCC8; SUR1; congenital hyperinsulinism; in vitro expression studies; molecular genetics; potassium channel