Minimizing carry-over PCR contamination in expanded CAG/CTG repeat instability applications

Area of Science:

• Molecular Biology
• Genetics
• Neurology

Background:

• Expanded CAG/CTG repeats are the cause of 14 neurological and neuromuscular disorders.
• Repeat tract size correlates with disease severity, and somatic instability affects disease progression.
• Current PCR methods for analyzing these repeats suffer from low yields, increasing contamination risk.

Purpose of the Study:

• To reduce carry-over contamination risk in PCR amplification of expanded CAG/CTG repeats.
• To optimize protocols for sequencing, cloning, and instability analysis of these repeats.
• To adapt existing methods for clinical diagnostics of repeat expansion disorders.

Main Methods:

• Pre-treating samples with Uracil N-Glycosylase (Ung) and using dUTP instead of dTTP in PCR.
• Applying Ung and dUTP PCR to amplification, sequencing, and cloning of expanded repeats.
• Optimizing small-pool PCR (SP-PCR) for use with Ung/dUTP protocols without compromising data quality.

Main Results:

• Successful PCR amplification, sequencing, and cloning of expanded CAG/CTG repeats using the Ung/dUTP method.
• Optimized SP-PCR demonstrated applicability to large expansions (up to 1000 repeats) in myotonic dystrophy samples.
• The new protocols maintain data quality while significantly reducing contamination risk.

Conclusions:

• The developed Ung/dUTP PCR protocols effectively reduce contamination risk in analyzing expanded CAG/CTG repeats.
• Optimized SP-PCR is suitable for clinical samples with large repeat expansions.
• These protocols are expected to benefit molecular diagnostics for expanded repeat disorders.