AGG interruptions within the maternal FMR1 gene reduce the risk of offspring with fragile X syndrome

Carolyn M. Yrigollen, Blythe Durbin-Johnson, Louise Gane, David L. Nelson, Randi J Hagerman, Paul J Hagerman, Flora Tassone

Research output: Contribution to journalArticlepeer-review

120 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)729-736
Number of pages8
JournalGenetics in Medicine
Issue number8
StatePublished - Aug 2012


  • AGG interruptions
  • CGG repeat
  • FMR1
  • genetic instability
  • premutation carriers

ASJC Scopus subject areas

  • Genetics(clinical)


Dive into the research topics of 'AGG interruptions within the maternal FMR1 gene reduce the risk of offspring with fragile X syndrome'. Together they form a unique fingerprint.

Cite this