title: Fragile X analysis of 1112 prenatal samples from 1991 to 2010.
abstract: OBJECTIVE
  To determine risks of expansion for normal, intermediate, and premutation FMR1 CGG repeats.
  
  
  METHODS
  PCR was used to compare the FMR1 alleles in prenatal (chorionic villi and amniocytes) and parental samples collected from 1991 to 2010. Prenatal diagnoses were confirmed by Southern analysis.
  
  
  RESULTS
  Fragile X analysis of 1112 pregnancies identified 558 normal, 106 intermediate, 216 premutation, and 232 full mutation fetuses. Of 509 maternal, intermediate, and premutation alleles, 350 (68.7%) were unstable on transmission with expansions ranging from one repeat to the full mutation. The smallest premutation alleles expanding to the full mutation were in mothers with 65 and 66 repeats. Transmissions from women with or without a family history of fragile X suggested greater instability in women from families that included full mutation expansions.
  
  
  CONCLUSIONS
  The maternal transmissions of alleles with 55 to 59 CGG repeats summarized here indicate that the risk for expansion to full mutation is substantially less than previous estimates for this size category. Most premutation alleles with no family history of fragile X exhibited less instability than those with a history of fragile X. Thus, lower risk estimates for full mutation expansion may be appropriate for women newly identified as premutation carriers through routine screening.
authors: Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY 10314, USA. sallynolin@gmail.com
authors: Sarah L
authors: SL
authors: Nolin
authors: Anne
authors: A
authors: Glicksman
authors: Xiaohua
authors: X
authors: Ding
authors: Nicole
authors: N
authors: Ersalesi
authors: W Ted
authors: WT
authors: Brown
authors: Stephanie L
authors: SL
authors: Sherman
authors: Carl
authors: C
authors: Dobkin
mesh_terms: D000328:Adult; D005260:Female; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics*; D005600:Fragile X Syndrome / Q000453:epidemiology / Q000235:genetics*; D005820:Genetic Testing; D042822:Genomic Instability; D006801:Humans; D008297:Male; D009035:Mothers; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D015995:Prevalence; D012307:Risk Factors; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*; D014481:United States / Q000453:epidemiology
chemical_list: D051860:Fragile X Messenger Ribonucleoprotein 1; C497683:FMR1 protein, human