A PCR-Free Hybrid Capture Approach for Detection of Pathogenic Repeat Expansions

Rebecca Barnard
Presented by
Rebecca Barnard, PhD
Rebecca Barnard, PhD
Bioinformatic Application Scientist, Manager, Twist Bioscience

At ASHG 2025, Rebecca Barnard, PhD (Twist Bioscience), presented new data demonstrating how a PCR-free, hybrid-capture sequencing workflow—developed through collaboration between Twist Bioscience and Element Biosciences—enables accurate detection of disease-causing short tandem repeat (STR) expansions. These repetitive sequences, known to underlie disorders such as Huntington’s disease, Fragile X syndrome, and myotonic dystrophy, have historically been difficult to resolve due to amplification bias, GC-rich regions, and somatic mosaicism. The combined Twist Enzymatic Fragmentation library prep with full-length adapters and Element’s Avidity Base Chemistry eliminates on-instrument PCR, improving coverage of complex, GC-dense loci and maintaining the original repeat structure. Barnard’s results showed clear detection of both normal and pathogenic alleles—including expanded DMPK genotypes (22/84 repeats)—while reducing hands-on time by up to five hours per workflow. The presentation highlights how this Trinity PCR-free solution advances repeat-expansion analysis with greater accuracy, speed, and scalability for research applications. 

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