PURPOSE: The ability to accurately predict the likelihood of expansion of the CGG repeats in the FMR1 gene to a full mutation is of critical importance for genetic counseling of women who are carriers of premutation alleles (55-200 CGG repeats) and who are weighing the risk of having a child with fragile X syndrome. The presence of AGG interruptions within the CGG repeat tract is thought to decrease the likelihood of expansion to a full mutation during transmission, thereby reducing risk, although their contribution has not been quantified. METHODS: We retrospectively analyzed 267 premutation alleles for number and position of AGG interruptions, length of pure CGG repeats, and CGG repeat lengths present in the offspring of the maternal transmissions. In addition, we determined the haplotypes of four markers flanking the 5'-UTR locus in the premutation mothers. RESULTS: We found that the presence of AGG interruptions significantly increased genetic stability, whereas specific haplotypes had a marginal association with transmission instability. CONCLUSION: The presence of AGG interruptions reduced the risk of transmission of a full mutation for all maternal (premutation) repeat lengths below ~100 CGG repeats, with a differential risk (0 vs. 2 AGG) exceeding 60% for alleles in the 70- to 80-CGG repeat range.
PURPOSE: The ability to accurately predict the likelihood of expansion of the CGG repeats in the FMR1 gene to a full mutation is of critical importance for genetic counseling of women who are carriers of premutation alleles (55-200 CGG repeats) and who are weighing the risk of having a child with fragile X syndrome. The presence of AGG interruptions within the CGG repeat tract is thought to decrease the likelihood of expansion to a full mutation during transmission, thereby reducing risk, although their contribution has not been quantified. METHODS: We retrospectively analyzed 267 premutation alleles for number and position of AGG interruptions, length of pure CGG repeats, and CGG repeat lengths present in the offspring of the maternal transmissions. In addition, we determined the haplotypes of four markers flanking the 5'-UTR locus in the premutation mothers. RESULTS: We found that the presence of AGG interruptions significantly increased genetic stability, whereas specific haplotypes had a marginal association with transmission instability. CONCLUSION: The presence of AGG interruptions reduced the risk of transmission of a full mutation for all maternal (premutation) repeat lengths below ~100 CGG repeats, with a differential risk (0 vs. 2 AGG) exceeding 60% for alleles in the 70- to 80-CGG repeat range.
Authors: Irina V Kovtun; Yuan Liu; Magnar Bjoras; Arne Klungland; Samuel H Wilson; Cynthia T McMurray Journal: Nature Date: 2007-04-22 Impact factor: 49.962
Authors: C B Kunst; C Zerylnick; L Karickhoff; E Eichler; J Bullard; M Chalifoux; J J Holden; A Torroni; D L Nelson; S T Warren Journal: Am J Hum Genet Date: 1996-03 Impact factor: 11.025
Authors: E E Eichler; J J Holden; B W Popovich; A L Reiss; K Snow; S N Thibodeau; C S Richards; P A Ward; D L Nelson Journal: Nat Genet Date: 1994-09 Impact factor: 38.330
Authors: G J Riggins; S L Sherman; B A Oostra; J S Sutcliffe; D Feitell; D L Nelson; B A van Oost; A P Smits; F J Ramos; E Pfendner Journal: Am J Med Genet Date: 1992 Apr 15-May 1
Authors: Sarah L Nolin; W Ted Brown; Anne Glicksman; George E Houck; Alice D Gargano; Amy Sullivan; Valérie Biancalana; Karen Bröndum-Nielsen; Helle Hjalgrim; Elke Holinski-Feder; Frank Kooy; John Longshore; James Macpherson; Jean-Louis Mandel; Gert Matthijs; Francois Rousseau; Peter Steinbach; Marja-Leena Väisänen; Harriet von Koskull; Stephanie L Sherman Journal: Am J Hum Genet Date: 2003-01-14 Impact factor: 11.025
Authors: Sarah L Nolin; Sachin Sah; Anne Glicksman; Stephanie L Sherman; Emily Allen; Elizabeth Berry-Kravis; Flora Tassone; Carolyn Yrigollen; Amy Cronister; Marcia Jodah; Nicole Ersalesi; Carl Dobkin; W Ted Brown; Raghav Shroff; Gary J Latham; Andrew G Hadd Journal: Am J Med Genet A Date: 2013-02-26 Impact factor: 2.802