Validation of a robust PCR-based assay for quantifying fragile X CGG repeats
Yvonne K Kwok1, Kit Man Wong1, Fai Man Lo2
1Department of Obstetrics and Gynaecology, Chinese University of Hong Kong, Hong Kong Special Administrative Region.
Summary
A new PCR assay accurately quantifies Fragile X (FMR1) CGG repeats, offering a reproducible and robust alternative to traditional methods for clinical laboratories.
Area of Science:
- Molecular Biology
- Genetics
- Clinical Diagnostics
Background:
- Traditional methods for sizing FMR1 trinucleotide repeats include PCR with capillary sequencing or Southern blot.
- These methods can be labor-intensive or require specialized equipment.
- Accurate quantification of CGG repeats is crucial for diagnosing Fragile X syndrome.
Purpose of the Study:
- To validate a new, accurate, and robust PCR assay for the quantification of CGG repeats in the FMR1 gene.
- To assess the performance of a PCR-based method utilizing a low-cost capillary electrophoresis instrument and the FragilEase™ reagent kit.
Main Methods:
- Analytical and clinical validation of a novel PCR assay.
- Testing on 12 Coriell reference samples (normal to full mutations) and 112 archived clinical DNA samples.
- Quantification of CGG repeat numbers using known standards and comparison with a reference method.
Main Results:
- Successful amplification of all tested samples, including 25 full mutation samples up to 1380 repeats.
- High concordance between the new assay and the reference method.
- Excellent intra-assay (CV<2.5%) and inter-assay imprecision, with variations within 1 CGG repeat.
Conclusions:
- The developed PCR-based method is reproducible and accurately identifies all Fragile X (FMR1) alleles.
- This assay is accurate and robust, making Fragile X testing more accessible.
- The method supports broader implementation in clinical laboratories.
