Tandem repeat knockout utilizing the CRISPR/Cas9 system in human cells

• CRISPR/Cas9-mediated tandem repeat knockout was proposed.
• Deletions up to 330 bp were demonstrated in the tandem repeats of MAGEL2.
• Off-target effects were identified for only one of the two sgRNAs used.

Tandem repeats have been shown to cause human genetic diseases and contribute significantly to genome variation and instability. Although multi-sgRNAs mediated CRISPR/Cas9 system have used to generate regional deletions previously, in this study we explored a method of generating regional deletions of tandem repeats by taking advantage of the off-target effects of CRISPR/Cas9 in 293FT cells. Our results revealed that generation of large-fragment deletions of tandem repeats located in the MAGEL2 and XIST gene was possible. In summary, we have demonstrated that large-fragment deletions of tandem repeats can be achieved using a sgRNA-directed CRISPR/Cas9 system, facilitating the functional study of tandem repeats in future studies.