Effect of gamma-ray exposure on the genome-editing efficiency of improved genome-editing via oviductal nucleic acids delivery (<i>i</i>-GONAD)

DNA double-strand breaks (DSBs) are among the most hazardous cellular damages, potentially leading to cell death or oncogenesis if unrepaired. Genome editing methods, such as the CRISPR/Cas9 system, induce DSBs and utilize these repair pathways for gene knockout and knock-in. Although ionizing radiation also induces DSBs, it is not clear whether the efficiency of genome editing is affected by ionizing radiation. This study investigated the impact of gamma-ray exposure on the genome editing efficiency of the improved genome editing via oviductal nucleic acid delivery (i-GONAD) method. Gamma-rays were exposed to pregnant mice receiving i-GONAD targeting the Hr gene, whose mutation causes hair loss in mice. The exposure on the fertilization day (Day 0) decreased natural delivery rates and litter sizes, with notable effects at 0.3 Gy or higher. Although the proportions of hairless offspring obtained by i-GONAD differed greatly between single-guide RNAs (sgRNAs) used, total mutation rates, including hairless, mosaic, and indel, were equivalent. Gamma-ray exposure on Day 0 and the day after fertilization (Day 1) similarly and almost dose-dependently enhanced the genome editing efficiency evaluated by the total mutation rate. This study suggests the improvement of genome editing efficiency by gamma-ray exposure, at least in i-GONAD method, potentially facilitating the creation of diverse experimental animal models.