Evaluation of Automated Magnetic Bead–Based DNA Extraction for Detection of Short Tandem Repeat Expansions With Nanopore Sequencing

Background

Long-read technologies such as nanopore sequencing provide new opportunities to detect short tandem repeat expansions. Therefore, a DNA extraction method is necessary that minimizes DNA fragmentation and hence allows the identification of large repeat expansions. In this study, an automated magnetic bead–based DNA extraction method and the required EDTA blood storage conditions as well as DNA and sequencing quality were evaluated for their suitability for repeat expansion detection with nanopore sequencing.

Methods

DNA was extracted from EDTA blood, and subsequently, its concentration, purity, and integrity were assessed. DNA was then subjected to nanopore sequencing, and quality metrics of the obtained sequencing data were evaluated.

Results

DNA extracted from fresh EDTA blood as well as from cooled or frozen EDTA blood revealed high DNA integrity whereas storage at room temperature over 7 days had detrimental effects. After nanopore sequencing, the read length N50 values of approximately 9 kb were obtained, and based on adaptive sampling of samples with a known repeat expansion, repeat expansions up to 10 kb could be detected.

Conclusion

The automated magnetic bead–based DNA extraction was sufficient to detect short tandem repeat expansions, omitting the need for high-molecular-weight DNA extraction methods. Therefore, DNA should be extracted either from fresh blood or from blood stored in cooled or frozen conditions. Consequently, this study may help other laboratories to evaluate their DNA extraction method regarding the suitability for detecting repeat expansions with nanopore sequencing.