title: Epigenetic modification of the X chromosome influences susceptibility to polycystic ovary syndrome.
abstract: BACKGROUND
  The cause of polycystic ovary syndrome (PCOS) is unknown, although genetic and environmental influences are clearly implicated. Some genetic studies have suggested the involvement of X-linked genes in PCOS, but the influence of X chromosome inactivation (XCI) on manifestation of this disorder has not previously been examined.
  
  
  OBJECTIVE
  The objective of the study was to test the null hypothesis that XCI has no influence on clinical presentation of PCOS.
  
  
  METHODS
  We examined patterns of XCI between sister pairs with the same genotype at a polymorphic locus on the X chromosome in families with PCOS.
  
  
  METHODS
  The study was conducted at a private practice.
  
  
  METHODS
  PCOS was defined as hyperandrogenemia with chronic anovulation. Forty families were studied in which DNA was obtained from at least one parent, the proband, and one sister that could be accurately diagnosed as being affected or unaffected.
  
  
  METHODS
  Relative expression of two X-linked alleles was determined, and the ratio of one to the other represented the pattern of XCI.
  
  
  RESULTS
  The statistical odds on a different clinical presentation between sisters was approximately 29 times higher in sister pairs with different patterns of XCI, compared with sister pairs with the same pattern of XCI (odds ratio 28.9; 95% confidence interval 4.0-206; P = 0.0008).
  
  
  CONCLUSIONS
  This study provides evidence to refute the null hypothesis and propose a closer inspection of X-linked genes in PCOS, one in which both genotype and epigenotype are considered. Environmental determinants of PCOS may alter clinical presentation via epigenetic modifications, which currently remain undetected in traditional genetic analyses.
authors.affiliation: Department of Obstetrics and Gynaecology, University of Adelaide, 1st Floor Maternity Building, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville, South Australia 5011, Australia. theresa.hickey@adelaide.edu.au
authors.forename: T E
authors.initials: TE
authors.lastname: Hickey
authors.forename: R S
authors.initials: RS
authors.lastname: Legro
authors.forename: R J
authors.initials: RJ
authors.lastname: Norman
mesh_terms: D041321:Chromosomes, Human, X / Q000235:genetics*; D044127:Epigenesis, Genetic / Q000235:genetics*; D005260:Female; D050172:Genes, X-Linked / Q000235:genetics; D020022:Genetic Predisposition to Disease; D006801:Humans; D010375:Pedigree; D011085:Polycystic Ovary Syndrome / Q000235:genetics*; D035781:Siblings; D049951:X Chromosome Inactivation / Q000235:genetics