FMR1 CGG expansions: Prevalence and sex ratios
Article first published online: 5 JUN 2013
Copyright © 2013 Wiley Periodicals, Inc.
American Journal of Medical Genetics Part B: Neuropsychiatric Genetics
Volume 162, Issue 5, pages 466–473, July 2013
How to Cite
2013. FMR1 CGG Expansions: Prevalence and Sex Ratios. Am J Med Genet Part B 162B:466–473., , , , , , , , , .
- Issue published online: 18 JUN 2013
- Article first published online: 5 JUN 2013
- Manuscript Accepted: 13 MAY 2013
- Manuscript Received: 29 JAN 2013
- Centers for Disease Control and Prevention. Grant Numbers: P30 HD03352, T32 HD007489-04
- National Institute of Child Health and Human Development
- Clinical and Translational Science Award (CTSA) Program
- NIH National Center for Advancing Translational Sciences (NCATS). Grant Numbers: UL1TR000427, U01HG004608, U01HG006389
- Fragile X;
- gray zone;
We have estimated the prevalence of FMR1 premutation and gray zone CGG repeat expansions in a population-based sample of 19,996 male and female adults in Wisconsin and compared the observed sex ratios of the prevalence of FMR1 CGG premutation and gray zone expansions to theoretical sex ratios. The female premutation prevalence was 1 in 148 and comparable to past research, but the male premutation prevalence of 1 in 290 is somewhat higher than most previous estimates. The female:male premutation prevalence ratio is in line with the theoretically predicted sex ratio. The prevalence of CGG repeats in the gray zone (45–54 repeats) was 1 in 33 females and 1 in 62 males. The prevalence of the “expanded” gray zone (defined here as 41–54 CGG repeats) was 1 in 14 females and 1 in 22 males, leading to a female:male ratio of 1.62 (95% confidence interval 1.39–1.90). This female:male ratio was significantly lower than the expected ratio of 2.0. We examined results from three previously published FMR1 prevalence studies and found similar female:male ratios for CGG repeats in this “expanded” gray zone range (pooled female:male ratio across all four studies 1.66, 95% confidence interval 1.51–1.82). Further research is needed to understand the apparent excess prevalence of males with CGG repeats in this range. © 2013 Wiley Periodicals, Inc.