Confirmation of the clinical diagnosis of fragile X syndrome by molecular tests is based on both the presence of a full mutation and methylation of the promotor region of the FMR1 gene. The mechanism leading to mosaic alleles of repeat number and the role of methylation in this process is still unde
Mosaicism for full mutation and normal-sized allele of the FMR1 gene: A new case
β Scribed by Orrico, Alfredo; Galli, Lucia; Dotti, Maria Teresa; Plewnia, Katrin; Censini, Stefano; Federico, Antonio
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 15 KB
- Volume
- 78
- Category
- Article
- ISSN
- 0148-7299
- DOI
- 10.1002/(sici)1096-8628(19980724)78:4<341::aid-ajmg7>3.0.co;2-o
No coin nor oath required. For personal study only.
β¦ Synopsis
The main mutation in fragile X patients is the expansion of the CGG repeat in the first exon of the FMR1 gene, associated with hypermethylation of the proximal CpG island. An increasing number of atypical cases have been reported showing the coexistence of full mutation and premutated or normalsized alleles. These genotypes are more difficult to detect, and if a PCR strategy alone is adopted, they can be incorrectly identified. We report on a fragile X man with severe phenotype and mosaicism for full mutation and a (CGG) 7 normal allele, the shortest fragment reported as yet in mosaics. This case of mosaicism, as other similar cases previously reported, suggests that the normal-length allele can derive from a deletion during the same early stage of development in which the full mutation expansion also arose. Am.
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