Achievements in 2024

Genome editing induces a double-strand break (DSB) at the target site to activate two endogenous DNA repair pathways in the cell: homology-directed repair (HDR) and non-homologous end joining (NHEJ). HDR is based on DNA recombination between the genomic DNA and homologous template DNA, which facilitates precise genome editing when the exogenous donor DNA is provided to the cells. In contrast, NHEJ is a template-free, error-prone repair mechanism in which the broken ends of DNA are joined together, often with random insertions or deletions (indels).

We are interested in how the balance between HDR and NHEJ is determined, and how we can enhance HDR. We previously reported that CRISPR-Cas9 systems with improved proof-reading enhance HDR (Nucleic Acids Res, 2018). To enhance HDR more, we focused on proteins involved in DNA repair and found that the fusion of Cas9 and Histones suppresses NHEJ (PLoS One, 2024).

Furthermore, we have analyzed the frequencies and combinations of HDR and NHEJ induced in single cells. We previously investigated genome editing outcomes in single human cultured cell lines such as HEK293T cells (iScience, 2022). We expanded this study to explore genome editing outcomes in single human iPS cells. We found that identical genetic modifications, including insertions and deletions with different lengths, tend to be induced in both alleles of single iPS cells (bioRxiv, 2024.09.18.613641).