Low dose irradiation enhances gene targeting in human pluripotent stem cells

Human pluripotent stem cells (hPSCs) are now being used for both disease modeling and cell therapy. However, efficient homologous recombination (HR) is often crucial to develop isogenic control or reporter lines. Here we show that limited low dose irradiation (LDI) using either γ-ray or X-ray exposure (0.4 Gy) significantly enhances HR frequency, possibly through induction of DNA repair/recombination machinery including ataxia-telangiectasia mutated, Histone H2A.X and RAD51 proteins. LDI could also increase HR efficiency by over 30- fold when combined with the targeting tools zinc finger nucleases (ZFNs), transcription activator–like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPRs). Whole exome sequencing confirmed that the LDI to hPSCs did not induce gross genomic alterations, or affect cellular viability. Irradiated and targeted lines were karyotypically normal and made all differentiated lineages that continued to express green fluorescent protein targeted at the AAVS1 locus. This simple method allows higher throughput of new targeted hPSC lines that are crucial for the research community as this growing field develops. 4 samples