Reference Panel for Fragile X Syndrome
Fragile X syndrome (OMIM #300624) affects approximately 1 in 3 000 males and 1 in 5 000 females.
It is caused by the expansion of the number of CGG repeats in the 5’-untranslated region of the Fragile X mental retardation 1 (FMR1) gene with consequent hypermethylation of promotor regions and shutdown of gene expression. There are four categories of allelic forms of CGGn repeat length:
- normal: <50 repeats
- intermediate (also referred to as ‘grey-zone’): 50-58 repeats
- premutation: 59- approx. 200 repeats
- full mutation > approx 200 repeats
The panel consists of 5 genomic DNA samples:
- normal female (consensus 22, 31 repeats)
- premutation female (consensus 33, 113 repeats)
- premutation male (consensus 114 repeats)
- full mutation female (consensus 38, 346 repeats)
- full mutation male (consensus 759 repeats)
Samples are presented as 23µg freeze dried genomic DNA in glass ampoules. The collaborative study indicates that these materials are suitable for use in Southern blot, PCR and Abbot PCR tests.
In addition, subsequent to the WHO collaborative study, the following data was obtained by two laboratories using the Asuragen PCR kit:
Assigned CGG repeat numbers (Hawkins et al, 2011) | Amplide X FMR1 PCR Kit results |
NIBSC code | Description | Mean | Lab 1 | Lab 2 |
|---|
07/120 | Female, wild-type | 22, 31 | 22, 31 | 22, 31 |
07/122 | Female, premutation | 33, 113 | 34, 105,116 | 34, 105,115 |
07/168 | Female, full mutation | 38, 346 | 39, >200 | 39, >200 |
07/170 | Male, full mutation | 754 | >200 | >200 |
07/174 | Male, premutation | 114 | 112, 119 | 112, 119 |
Reference:
Hawkins M et al. (2011) Preparation and validation of the first WHO international genetic reference panel for Fragile X syndrome. Eur J Hum Genet. 19:10-7.
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