Technology Overview

Expansion of simple sequence repeats that are dispersed throughout the human genome directly cause many genetic human diseases, such as:

• fragile X syndrome (FXS), which is caused by CGG trinucleotide repeats;
• fragile XE non-syndromic intellectual disability (FRAXE NSID), caused by CCG repeats;
• Huntington disease and spinocerebellar ataxias (CAG repeats); and among many others.

Such genetic diseases are known as repeat expansion disorders and are usually difficult to distinguish by signs and symptoms alone due to extensive clinical overlap and other accompanying phenotypes. For example, FXS and FRAXE NSID are strongly associated with intellectual disabilities, but the mild-to-borderline phenotype of FRAXE NSID could lead to under-diagnosis as compared to FXS.

As such, separate molecular genetic testing is necessary to diagnose each disease, which inevitably adds to the time and costs. Further, time, effort and reagent costs are proportionately higher when many genes have to be tested to identify the causative disease gene for a condition.

Given the above, the technology provides a solution that allows such repeat expansion disorders to be detected simultaneously in a single-tube reaction. Using a single common primer, multiple expansion mutations that have same trinucleotide repeat sequences can be detected rapidly using triplet-primed PCR (TP-PCR) and capillary electrophoresis.

Technology Features, Specifications and Advantages

The strategy of the technology employs a single-tube assay to screen multiple genetic loci responsible for different repeat expansion disorders that are caused by expansion of the same type of repeat.

This technology uses triplet-primed PCR (TP-PCR) to detect and amplify the expansion mutations that have same trinucleotide repeat sequences using a single common primer. This is followed by distinguishing the amplified product using capillary electrophoresis by a combination of its size range and its fluorescence tag.

Advantages :

• A single-tube reaction which requires a sample and one capillary electrophoresis run per sample – for detecting multiple disease genes.
• Significant savings in time, effort and reagent and equipment usage costs compared to individual analysis of each gene locus.

Potential Applications

The strategy of the technology allows repeat expansion disorders with many possible causative genes, but whose repeat sequence contain identical repeating units, to be rapidly screened for the causative expansion mutation at a cost not much higher than one single locus screen.

This technology has been applied to detecting and differentiating :

• Fragile X Syndrome (FXS) and Fragile XE non-syndromic intellectual disability (FRAXE NSID); and
• seven types of spinocerebellar ataxias (CAG repeats).

This technology can potentially be used for large scale screening.

Customer Benefit

This technology allows simultaneous detection of common repeat expansion in a more rapid and cost-effective manner. Ultimately, individuals will benefit from the time and cost-savings for testing multiple repeat expansion disorders with a single sample and assay.