Massively parallel sequencing of ataxia genes after array-based enrichment

Area of Science:

• Genomics
• Molecular Biology
• Genetic Diagnostics

Background:

• Massively parallel sequencing (MPS) offers significant diagnostic potential for genetic disorders.
• Enrichment of target DNA regions is crucial for efficient and accurate MPS analysis.
• Genetically heterogeneous disorders require robust methods for variant detection.

Purpose of the Study:

• To validate an array-based sequence capture method for enrichment of target genes in genetically heterogeneous disorders.
• To assess the diagnostic utility of MPS following sequence capture for detecting mutations in AR ataxia.
• To determine the required sequencing coverage for reliable variant detection.

Main Methods:

• Developed a 2-Mb sequence-capture array targeting seven disease genes and two control loci for AR ataxia.
• Enriched DNA samples from patients with known mutations and controls using the array.
• Performed MPS using Roche GS FLX Titanium, analyzing an average of 65 Mb per sample.
• Validated variant detection for deletions, point mutations, and single nucleotide polymorphisms (SNPs).

Main Results:

• Achieved an average of 25-fold coverage per base in targeted regions, with 80% of reads on target.
• Successfully detected 6/7 mutant alleles, including deletions and point mutations, with >99% accuracy for known SNPs.
• Observed reduced coverage in repeat-rich regions, highlighting a limitation for variant detection.
• Recommended a minimum coverage of 15-fold for diagnostic implementation.

Conclusions:

• Array-based sequence capture coupled with MPS is a validated approach for personalized diagnosis of heterogeneous genetic disorders.
• The method demonstrates high specificity and accuracy for detecting various genomic variants.
• Further optimization is needed to address challenges in repeat-rich regions for comprehensive variant detection.