Challenges facing genetic diagnostics of Huntington's disease: an update

Area of Science:

• Genetics
• Neurology
• Molecular Biology

Background:

• Huntington's disease (HD) diagnosis historically relies on fragment analysis of CAG trinucleotide repeats in the HTT gene.
• Sequence variations and interruptions within the HTT repeat influence HD onset and clinical presentation.
• Traditional PCR and capillary electrophoresis struggle to detect these complex repeat anomalies.

Purpose of the Study:

• To highlight the limitations of current genetic diagnostic methods for Huntington's disease.
• To introduce long-read sequencing (LRS) as a superior technology for analyzing complex repeat expansions.
• To emphasize the clinical relevance of identifying non-canonical repeat motifs and sequence variations.

Main Methods:

• Review of existing literature and clinical data on Huntington's disease genetic diagnostics.
• Comparison of fragment analysis, next-generation sequencing (NGS) with short reads, and long-read sequencing (LRS).
• Focus on the technical capabilities of LRS in resolving complex repeat structures.

Main Results:

• Fragment analysis and short-read NGS have limitations in detecting interrupted or non-canonical repeat sequences.
• Long-read sequencing (LRS) provides read lengths over 10 kb, enabling detailed analysis of repeat sequences.
• LRS can identify complex alternating sequence motifs, offering potentially crucial clinical information.

Conclusions:

• Long-read sequencing (LRS) represents a significant advancement for the genetic diagnosis of Huntington's disease.
• LRS overcomes the limitations of short-read technologies in characterizing complex repeat expansions.
• Accurate identification of repeat variations using LRS can lead to a better understanding of HD pathogenesis and clinical outcomes.