title: Novel variants in growth differentiation factor 9 in mothers of dizygotic twins.
abstract: BACKGROUND
  Genes from the ovarian bone morphogenetic signaling pathway (GDF9 and BMP15) are critical for normal human fertility. We previously identified a deletion mutation in GDF9 in sisters with spontaneous dizygotic (DZ) twins, but the prevalence of rare GDF9 variants in twinning families is unknown.
  
  
  OBJECTIVE
  The objective was to evaluate the frequency of rare variants in GDF9 in families with a history of DZ twinning.
  
  
  METHODS
  We recruited 3450 individuals from 915 DZ twinning families (1693 mothers of twins) and 1512 controls of Caucasian origin. One mother of DZ twins was selected from 279 of the 915 families, and a DNA sample was screened for rare variants in GDF9 using denaturant HPLC. Variants were confirmed by DNA sequencing and genotyped in the entire sample by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry.
  
  
  RESULTS
  We found two novel insertion/deletions (c.392-393insT, c.1268-1269delAA) and four missense alterations in the GDF9 sequence in mothers of twins. Two of the missense variants (c.307C > T, p.Pro103Ser and c.362C > T, p.Thr121Leu) were located in the pro-region of GDF9 and two (c.1121C > T, p.Pro374Leu and c.1360C > T, p.Arg454Cys) in the mature protein region. For each variant, the frequencies were higher in cases compared with controls. The proportion of mothers of DZ twins carrying any variant (4.12%) was significantly higher (P < 0.0001) than the proportion of carriers in controls (2.29%).
  
  
  CONCLUSIONS
  We describe new variants in the GDF9 gene that are significantly more common in mothers of DZ twins than controls, suggesting that rare GDF9 variants contribute to the likelihood of DZ twinning.
authors.affiliation: Molecular Epidemiology, Queensland Institute of Medical Research, Brisbane, QLD 4029, Australia.
authors.forename: James S
authors.initials: JS
authors.lastname: Palmer
authors.forename: Zhen Zhen
authors.initials: ZZ
authors.lastname: Zhao
authors.forename: Chantal
authors.initials: C
authors.lastname: Hoekstra
authors.forename: Nicholas K
authors.initials: NK
authors.lastname: Hayward
authors.forename: Penelope M
authors.initials: PM
authors.lastname: Webb
authors.forename: David C
authors.initials: DC
authors.lastname: Whiteman
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Martin
authors.forename: Dorret I
authors.initials: DI
authors.lastname: Boomsma
authors.forename: David L
authors.initials: DL
authors.lastname: Duffy
authors.forename: Grant W
authors.initials: GW
authors.lastname: Montgomery
mesh_terms: D055430:Bone Morphogenetic Protein 15; D035061:Control Groups; D005260:Female; D017353:Gene Deletion; D005787:Gene Frequency; D005820:Genetic Testing; D014644:Genetic Variation; D055429:Growth Differentiation Factor 9; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics*; D009035:Mothers; D010375:Pedigree; D011110:Polymorphism, Genetic; D011247:Pregnancy; D014429:Twins, Dizygotic / Q000235:genetics
chemical_list: C525901:BMP15 protein, human; D055430:Bone Morphogenetic Protein 15; C525897:GDF9 protein, human; D055429:Growth Differentiation Factor 9; D036341:Intercellular Signaling Peptides and Proteins