PacBio’s Jenny Ekholm presents this ASHG 2016 poster on a new method being developed that enriches for unamplified DNA and uses SMRT Sequencing to characterize repeat expansion disorders. Incorporating the CRISPR/Cas9 system to target specific genes allows for amplification-free enrichment to preserve epigenetic information and avoid PCR bias. Internal studies have shown that the approach can successfully be used to target and sequence the CAG repeat responsible for Huntington’s disease, the repeat associated with ALS, and more. The approach allows for pooling many samples and sequencing with a single SMRT Cell.
Targeted sequencing of genomic DNA requires an enrichment method to generate detectable amounts of sequencing products. Genomic regions with extreme composition bias and repetitive sequences can pose a significant enrichment challenge. Many genetic diseases caused by repeat element expansions are representative of these challenging enrichment targets. PCR amplification, used either alone or in combination with a hybridization capture method, is a common approach for target enrichment. While PCR amplification can be used successfully with genomic regions of moderate to high complexity, it is the low-complexity regions and regions containing repetitive elements sometimes of indeterminate lengths due to repeat expansions that…
Genomic regions with extreme base composition bias and repetitive sequences have long proven challenging for targeted enrichment methods, as they rely upon some form of amplification. Similarly, most DNA sequencing technologies struggle to faithfully sequence regions of low complexity. This has especially been true for repeat expansion disorders such as Fragile X syndrome, Huntington’s disease and various Ataxias, where the repetitive elements range from several hundreds of bases to tens of kilobases. We have developed a robust, amplification-free targeted enrichment technique, called No-Amp Targeted Sequencing, that employs the CRISPR/Cas9 system. In conjunction with Single Molecule, Real-Time (SMRT) Sequencing, which delivers…
Nucleotide repeat expansions are a major cause of neurological and neuromuscular disease in humans, however, the nature of these genomic regions makes characterizing them extremely challenging. Accurate DNA sequencing of repeat expansions using short-read sequencing technologies is difficult, as short-read technologies often cannot read through regions of low sequence complexity. Additionally, these short reads do not span the entire region of interest and therefore sequence assembly is required. Lastly, most target enrichment methods are reliant upon amplification which adds the additional caveat of PCR bias. We have developed a novel, amplification-free enrichment technique that employs the CRISPR/Cas9 system for specific…
The World Health Organization reports that antibiotic-resistant pathogens represent an imminent global health disaster for the 21st century. Gram-positive superbugs threaten to breach last-line antibiotic treatment, and the pharmaceutical industry antibiotic development pipeline is waning. Here we report the synergy between ionophore-induced physiological stress in Gram-positive bacteria and antibiotic treatment. PBT2 is a safe-for-human-use zinc ionophore that has progressed to phase 2 clinical trials for Alzheimer’s and Huntington’s disease treatment. In combination with zinc, PBT2 exhibits antibacterial activity and disrupts cellular homeostasis in erythromycin-resistant group A Streptococcus (GAS), methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE). We were unable to…