How to cite this article: Dobkin C, Radu G, Ding X-H, Brown WT, Nolin SL. 2009. Fragile X prenatal analyses show full mutation females at high risk for mosaic Turner syndrome: Fragile X leads to chromosome loss. Am J Med Genet Part A 149A:2152–2157.
Fragile X prenatal analyses show full mutation females at high risk for mosaic Turner syndrome: Fragile X leads to chromosome loss†
Article first published online: 16 SEP 2009
Copyright © 2009 Wiley-Liss, Inc.
American Journal of Medical Genetics Part A
Volume 149A, Issue 10, pages 2152–2157, October 2009
How to Cite
Dobkin, C., Radu, G., Ding, X.-H., Brown, W. T. and Nolin, S. L. (2009), Fragile X prenatal analyses show full mutation females at high risk for mosaic Turner syndrome: Fragile X leads to chromosome loss. Am. J. Med. Genet., 149A: 2152–2157. doi: 10.1002/ajmg.a.33011
- Issue published online: 24 SEP 2009
- Article first published online: 16 SEP 2009
- Manuscript Accepted: 15 JUN 2009
- Manuscript Received: 9 FEB 2009
- Centers for Disease Control and Prevention
- New York State Office of Mental Retardation and Developmental Disabilities
- fragile X;
- prenatal diagnosis;
- mosaic turner syndrome;
- amplified fragment length polymorphism analysis
The fragile X mutation is an expansion of a CGG triplet repeat in the 5′ untranslated region of the FMR1 gene. Expansion to >200 repeats (the “full mutation”) silences FMR1 transcription and leads to the fragile X mental retardation syndrome in males and in some females. It also affects the structure of the mitotic chromosome as evidenced by a folate sensitive fragile site. Isolated cases of 45,X/46,XX (mosaic Turner syndrome) in full mutation females have been reported but an increased prevalence was not apparent from these reports. PCR and Southern analysis of the CGG repeat in 423 prenatal female samples identified 106 full mutation cases. Surprisingly five of these had 45,X/4,6XX mosaicism while none of the other 317 female fetuses did. In two of the five cases ≥50% of the cells were reported to be 45,X and in the other three, ≤14%. We investigated the association of the full mutation and mosaic Turner syndrome using polymorphisms and single cell cloning to identify the X chromosome that was lost. Our analysis indicates that at least four of the five full mutation mosaicism cases were due to loss of the maternal, full mutation chromosome. These data indicate that 45,X/46,XX mosaicism is much more common than expected in fragile X full mutation females. Moreover, they suggest that the presence of the fragile X full mutation on a chromosome may predispose it to loss during mitosis, possibly due to the altered structure of the metaphase fragile X chromosome. © 2009 Wiley-Liss, Inc.