title: The A645D mutation in the hinge region of the human androgen receptor (AR) gene modulates AR activity, depending on the context of the polymorphic glutamine and glycine repeats.
abstract: BACKGROUND
  Sufficient androgen receptor (AR) activity is crucial for normal male sexual differentiation. Here we report on two unrelated 46, XY patients suffering from undervirilization and genital malformations. Both patients had a short polyglycine (polyG) repeat of 10 residues and a relatively long polyglutamine (polyQ) repeat of 28 and 30 residues within the transactivation domain of the AR. In addition, they also harbor a rare A645D substitution.
  
  
  OBJECTIVE
  We made a set of AR expression plasmid constructs with varying polyQ and polyG tract sizes in context with or without the A645D substitution and analyzed their in vitro transactivation capacity in transfected CHO cells.
  
  
  RESULTS
  We found that a short polyG repeat downmodulated AR activity to approximately 60-65% of the wild-type receptor. This effect was aggravated by A645D in context of a long polyQ repeat to less than 50% activity. In contrast, in the context of a short polyQ and a short polyG repeat, the A645D mutation rescues AR activity to almost wild-type levels, demonstrating a contradictory effect of this mutation, depending on the size of the polymorphic repeats.
  
  
  CONCLUSIONS
  A combination of a short polyG repeat with a long polyQ repeat and an A645D substitution might contribute to the development of virilization disorders and explain the observed phenotypes of our patients as a form of androgen insensitivity. The whole recreation of AR sequence variations including individual polymorphic repeat sizes could unravel possible interference of mutations and variations on AR activity by in vitro transfection.
authors.affiliation: Department of Pediatric and Adolescent Medicine, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Werner
authors.forename: Paul-Martin
authors.initials: PM
authors.lastname: Holterhus
authors.forename: Gerhard
authors.initials: G
authors.lastname: Binder
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Schwarz
authors.forename: Michel
authors.initials: M
authors.lastname: Morlot
authors.forename: Dagmar
authors.initials: D
authors.lastname: Struve
authors.forename: Christine
authors.initials: C
authors.lastname: Marschke
authors.forename: Olaf
authors.initials: O
authors.lastname: Hiort
mesh_terms: D013734:Androgen-Insensitivity Syndrome / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D006224:Cricetinae; D014644:Genetic Variation; D006801:Humans; D007223:Infant; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D010957:Plasmids / Q000235:genetics; D017354:Point Mutation; D011068:Poly G / Q000235:genetics / Q000378:metabolism; D011944:Receptors, Androgen / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics; D014162:Transfection
chemical_list: C410798:AR protein, human; D011944:Receptors, Androgen; D011068:Poly G