title: NNT pseudoexon activation as a novel mechanism for disease in two siblings with familial glucocorticoid deficiency.
abstract: BACKGROUND
  Intronic DNA frequently encodes potential exonic sequences called pseudoexons. In recent years, mutations resulting in aberrant pseudoexon inclusion have been increasingly recognized to cause disease.
  
  
  OBJECTIVE
  To find the genetic cause of familial glucocorticoid deficiency (FGD) in two siblings.
  
  
  METHODS
  The proband and his affected sibling, from nonconsanguineous parents of East Asian and South African origin, were diagnosed with FGD at the ages of 21 and 8 months, respectively.
  
  
  METHODS
  Whole exome sequencing was performed on genomic DNA (gDNA) of the siblings. Variants in genes known to cause FGD were assessed for causality. Further analysis of gDNA and cDNA was performed by PCR/RT-PCR followed by automated Sanger sequencing.
  
  
  RESULTS
  Whole exome sequencing identified a single, novel heterozygous variant (p.Arg71*) in nicotinamide nucleotide transhydrogenase (NNT) in both affected individuals. Follow-up cDNA analysis in the proband identified a 69-bp pseudoexon inclusion event, and Sanger sequencing of his gDNA identified a 4-bp duplication responsible for its activation. The variants segregated with the disease: p.Arg71* was inherited from the mother, the pseudoexon change was inherited from the father, and an unaffected sibling had inherited only the p.Arg71* variant.
  
  
  CONCLUSIONS
  FGD in these siblings is caused by compound heterozygous mutations in NNT; one causing pseudoexon inclusion in combination with another leading to Arg71*. Discovery of this pseudoexon activation mutation highlights the importance of identifying sequence changes in introns by cDNA analysis. The clinical implications of these findings include: facilitation of antenatal genetic diagnosis, early institution of potentially lifesaving therapy, and the possibility of preventative or curative intervention.
authors.affiliation: Centre for Endocrinology (T.V.N., L.F.C., L.A.M.), William Harvey Research Institute, John Vane Science Centre, Queen Mary, University of London, London, EC1M 6BQ, United Kingdom; Department of Endocrinology (S.R.R., G.P., C.S.C.), Princess Margaret Hospital, Child and Adolescent Services, Subiaco, Perth, Western Australia 6008; Department of Diagnostic Genomics (K.C.), PathWest Laboratory Medicine, Nedlands, Western Australia 6009; Genetic Services of Western Australia (N.P.), King Edward Memorial Hospital, Subiaco, Western Australia 6008; and School of Pediatrics and Child Health (S.R.R., N.P., C.S.C.), and School of Women's and Infants' Health (J.E.D.), University of Western Australia, Perth, Australia 6009.
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Novoselova
authors.forename: Shoshana R
authors.initials: SR
authors.lastname: Rath
authors.forename: Karen
authors.initials: K
authors.lastname: Carpenter
authors.forename: Nicholas
authors.initials: N
authors.lastname: Pachter
authors.forename: Jan E
authors.initials: JE
authors.lastname: Dickinson
authors.forename: Glynis
authors.initials: G
authors.lastname: Price
authors.forename: Li F
authors.initials: LF
authors.lastname: Chan
authors.forename: Catherine S
authors.initials: CS
authors.lastname: Choong
authors.forename: Louise A
authors.initials: LA
authors.lastname: Metherell
mesh_terms: D000309:Adrenal Insufficiency / Q000235:genetics*; D005260:Female; D006801:Humans; D007223:Infant; D007438:Introns; D008297:Male; D009250:NADP Transhydrogenases / Q000235:genetics*; D010375:Pedigree; D035781:Siblings
chemical_list: D009250:NADP Transhydrogenases