title: A novel missense mutation in the HSD3B2 gene, underlying nonsalt-wasting congenital adrenal hyperplasia. new insight into the structure-function relationships of 3β-hydroxysteroid dehidrogenase type II.
abstract: BACKGROUND
  3βHSD2 is a bifunctional microsomal NAD+-dependent enzyme crucial for adrenal and gonad steroid biosynthesis, converting Δ5-steroids to Δ4-steroids. 3βHSD2 deficiency is a rare cause of congenital adrenal hyperplasia caused by recessive loss-of-function HSD3B2 mutations.
  
  
  OBJECTIVE
  The aim was to define the pathogenic consequences of a novel missense mutation in the HSD3B2 gene.
  
  
  METHODS
  We report a 7-month-old 46,XX girl referred because of precocious pubarche and postnatal clitoromegaly. Hormonal profile showed inadequate glucocorticoid levels, increased 17OHP and renin levels, and very high DHEAS levels, suggestive of compensated nonsalt-losing 3βHSD2 deficiency.
  
  
  RESULTS
  Direct sequencing revealed a novel, homozygous, pG250V HSD3B2 mutation. In vitro analysis in intact COS-7 cells showed impaired enzymatic activity for the conversion of pregnenolone to progesterone and dehydroepiandrosterone to androstenedione (20% and 27% of WT at 6 h, respectively). G250V-3βHSD2 decreased the Vmax for progesterone synthesis without affecting the Km for pregnenolone. Western blot and immunofluorescence suggested that p.G250V mutation has no effect on the expression and intracellular localization of the mutant protein. Molecular homology modeling predicted that mutant V250 affected an L239-Q251 loop next to a β-sheet structure in the NAD+-binding domain.
  
  
  CONCLUSIONS
  We identified a novel p.G250V mutation of HSD3B2 which causes an incomplete loss of enzymatic activity, explaining the compensated nonsalt loss phenotype. In vitro and in silico experiments provided insight into the structure-function relationship of the 3βHSD2 protein suggesting the importance of the L239-Q251 loop for the catalytic activity of the otherwise stable 3βHSD2 enzyme.
authors.affiliation: Endocrine Service (M.S.B., M.C., R.M., N.P.G., P.R., M.M., M.A.R., A.B.), Hospital de Pediatria Garrahan, CONICET, Buenos Aires, Argentina; Biological Chemistry Department (A.T., L.A.D.), Instituto de Química Física de los Materiales Medio Ambiente y Energia (INQUIMAE)-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: María Sonia
authors.initials: MS
authors.lastname: Baquedano
authors.forename: Marta
authors.initials: M
authors.lastname: Ciaccio
authors.forename: Roxana
authors.initials: R
authors.lastname: Marino
authors.forename: Natalia
authors.initials: N
authors.lastname: Perez Garrido
authors.forename: Pablo
authors.initials: P
authors.lastname: Ramirez
authors.forename: Mercedes
authors.initials: M
authors.lastname: Maceiras
authors.forename: Adrian
authors.initials: A
authors.lastname: Turjanski
authors.forename: Lucas A
authors.initials: LA
authors.lastname: Defelipe
authors.forename: Marco A
authors.initials: MA
authors.lastname: Rivarola
authors.forename: Alicia
authors.initials: A
authors.lastname: Belgorosky
mesh_terms: D000312:Adrenal Hyperplasia, Congenital / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D007223:Infant; D020125:Mutation, Missense; D011375:Progesterone Reductase / Q000235:genetics* / Q000378:metabolism; D011629:Puberty, Precocious / Q000235:genetics* / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: C533068:3 beta-hydroxysteroid dehydrogenase type II; D011375:Progesterone Reductase