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Genetic diagnostic technique for SCA1-3,6,7

Molecular diagnosisPCRSCASpinocerebellar ataxiaTriplet repeat

Introduction

Spinocerebellar Ataxias (SCA) are a group of hereditary autosomal-dominant neurodegenerative diseases. Following EMQN guidelines, the “Tethering PCR” technique has been developed so that a molecular genetics laboratory could rapidly, reliably and affordably diagnose the five most common SCA subtypes: SCA1, 2, 3, 6, and 7.

Technical features

At present, there are no standardized techniques for the molecular diagnosis of SCAs. Moreover, to complete the diagnosis laboratories are often required to perform second-level tests that are both expensive and time-consuming. Thanks to the optimized PCR protocols and automatic sequencer runs, our technique allows the rapid and simultaneous testing of SCA1, 2, 3, 6, and 7. The patented “Tethering PCR” technique allows to clearly discriminate between normal and affected subjects  counting the number of CAG trinucleotide repeats in both alleles, without using second-level techniques. These repeats, encoding for the Glutamine amino acid, are associated to the disease if they exceed a given number (different for each SCA subtype). Moreover, the number of repeats may correlate with both with the age at onset and the severity of the disease.

Possible Applications

  • Molecular diagnosis of SCA1, 2, 3, 6, 7 in a medical genetics laboratory;
  • The same technique could be modified for the application in other genetic diseases caused by polynucleotide expansions.

Advantages

  • Faster compared to tradional techniques;
  • Allows counting CAG repeats;
  • Allows discriminating between homozygous and heterozygous subjects;
  • No second-level testing needed.