title: Mutational analysis of the necdin gene in patients with congenital isolated hypogonadotropic hypogonadism.
abstract: BACKGROUND
  Necdin activates GNRH gene expression and is fundamental for the development, migration, and axonal extension of murine GNRH neurons. In humans, necdin plays a potential role in the hypogonadotropic hypogonadism phenotype in patients with Prader-Willi syndrome.
  
  
  OBJECTIVE
  To investigate necdin gene (NDN) variants in patients with isolated hypogonadotropic hypogonadism (IHH).
  
  
  METHODS
  We studied 160 Brazilian patients with IHH, which includes 92 with Kallmann syndrome and 68 with normosmic IHH. Genomic DNA was extracted and the single NDN exon was amplified and sequenced. To measure GNRH transcriptional activity, luciferase reporter plasmids containing GNRH regulatory regions were transiently transfected into GT1-7 cells in the presence and absence of overexpressed wild-type or mutant necdin.
  
  
  RESULTS
  A heterozygous variant of necdin, p.V318A, was identified in a 23-year-old male with Kallmann syndrome. The p.V318A was also present in affected aunt and his father and was absent in 100 Brazilian control subjects. Previous FGFR1 gene analysis revealed a missense mutation (p.P366L) in this family. Functional studies revealed a minor difference in the activation of GNRH transcription by mutant protein compared with wild type in that a significant impairment of the necdin protein activity threshold was observed.
  
  
  CONCLUSIONS
  A rare variant of necdin (p.V318A) was described in a family with Kallmann syndrome associated with a FGFR1 mutation. Familial segregation and in vitro analysis suggested that this non-synonymous variant did not have a direct causative role in the hypogonadism phenotype. NDN mutations are not a frequent cause of congenital IHH.
authors.affiliation: Unidade de Endocrinologia do Desenvolvimento, Laboratório de Hormônios e Genética Molecular/LIM42, Hospital das Clinicas da Faculdade de Medicina da Universidade de São Paulo, Avenida Doutor Eneas de Carvalho Aguiar 155, 2° Andar, Bloco 6, CEP 05403-900 São Paulo, São Paulo, Brazil. daianebeneduzzi@yahoo.com.br
authors.forename: Daiane
authors.initials: D
authors.lastname: Beneduzzi
authors.forename: Anita K
authors.initials: AK
authors.lastname: Iyer
authors.forename: Ericka Barbosa
authors.initials: EB
authors.lastname: Trarbach
authors.forename: Acacio P
authors.initials: AP
authors.lastname: Silveira-Neto
authors.forename: Letícia G
authors.initials: LG
authors.lastname: Silveira
authors.forename: Cintia
authors.initials: C
authors.lastname: Tusset
authors.forename: Kathleen
authors.initials: K
authors.lastname: Yip
authors.forename: Berenice B
authors.initials: BB
authors.lastname: Mendonça
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Mellon
authors.forename: Ana Claudia
authors.initials: AC
authors.lastname: Latronico
mesh_terms: D000818:Animals; D001483:Base Sequence; D001938:Brazil; D004252:DNA Mutational Analysis; D005260:Female; D006801:Humans; D007006:Hypogonadism / Q000151:congenital / Q000235:genetics*; D017436:Kallmann Syndrome / Q000235:genetics; D008297:Male; D051379:Mice; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010375:Pedigree; D011218:Prader-Willi Syndrome / Q000235:genetics*; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000235:genetics
chemical_list: D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; C069766:necdin; C496348:FGFR1 protein, human; D051496:Receptor, Fibroblast Growth Factor, Type 1