title: Identification and functional analysis of novel dual oxidase 2 (DUOX2) mutations in children with congenital or subclinical hypothyroidism.
abstract: BACKGROUND
  Congenital hypothyroidism (CH) associated with goiter or a gland of normal size has been linked to dual oxidase 2 (DUOX2) mutations in the presence of iodide organification defect.
  
  
  OBJECTIVE
  Thirty unrelated children with CH or subclinical hypothyroidism (SH) identified during infancy with a eutopic thyroid gland, coming from our Screening Centre for CH or referred from other regions of Italy, were studied with the perchlorate discharge test to identify organification defects. Eleven children with iodide organification defect were considered for the genetic analysis of TPO, DUOX2, and dual oxidase maturation factor 2 (DUOXA2) genes.
  
  
  METHODS
  Eight children with CH and three with SH and eutopic thyroid gland were included in the study. After discontinuation of therapy, a partial or complete organification defect was shown after ¹²³I scintigraphy and perchlorate test.
  
  
  METHODS
  TPO, DUOX2, and DUOXA2 genes were analyzed, and functional activity of DUOX2 variants was studied in HeLa cells.
  
  
  RESULTS
  Sequencing of the DUOX2 gene revealed a deletion S965fsX994 in three children; two were euthyroid after 1 month of L-T₄ discontinuation but developed SH after 5 and 18 months, respectively, whereas the other child had SH. One child with SH showed H678R, R701Q, and P982A substitutions, and another child with SH showed only the P982A. One child with SH showed the Y1150C mutation, and another euthyroid child showed the A728T mutation. Functional studies confirmed that S965fsX994, Y1150C, and A728T mutations were responsible for the defect in H₂O₂ production, whereas H678R, R701Q, and P982A did not alter H₂O₂ production in vitro.
  
  
  CONCLUSIONS
  Genetic analysis of the DUOX2 gene was performed in 11 children with organification defect. Two new mutations (Y1150C and A728T) and the deletion S965FsX994 were responsible for the deficit in the organification process and the phenotypes. Three polymorphisms (H678R, P982A, and R701Q) were identified.
authors.affiliation: Dipartimento di Endocrinologia, Università di Pisa, Via Paradisa 2, 56124, Cisanello, Pisa, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: De Marco
authors.forename: Patrizia
authors.initials: P
authors.lastname: Agretti
authors.forename: Lucia
authors.initials: L
authors.lastname: Montanelli
authors.forename: Caterina
authors.initials: C
authors.lastname: Di Cosmo
authors.forename: Brunella
authors.initials: B
authors.lastname: Bagattini
authors.forename: Melissa
authors.initials: M
authors.lastname: De Servi
authors.forename: Eleonora
authors.initials: E
authors.lastname: Ferrarini
authors.forename: Antonio
authors.initials: A
authors.lastname: Dimida
authors.forename: Andrea Claudia
authors.initials: AC
authors.lastname: Freitas Ferreira
authors.forename: Angelo
authors.initials: A
authors.lastname: Molinaro
authors.forename: Claudia
authors.initials: C
authors.lastname: Ceccarelli
authors.forename: Federica
authors.initials: F
authors.lastname: Brozzi
authors.forename: Aldo
authors.initials: A
authors.lastname: Pinchera
authors.forename: Paolo
authors.initials: P
authors.lastname: Vitti
authors.forename: Massimo
authors.initials: M
authors.lastname: Tonacchera
mesh_terms: D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003409:Congenital Hypothyroidism / Q000235:genetics* / Q000503:physiopathology; D000074623:Dual Oxidases; D005260:Female; D017353:Gene Deletion; D006367:HeLa Cells; D006801:Humans; D008297:Male; D008875:Middle Aged; D019255:NADPH Oxidases / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D017354:Point Mutation; D012720:Severity of Illness Index; D013961:Thyroid Gland / Q000502:physiology
chemical_list: D000074623:Dual Oxidases; D019255:NADPH Oxidases; C431515:DUOX2 protein, human