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Low dose irradiation enhances gene targeting in human pluripotent stem cells

ABSTRACT: 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.

ORGANISM(S): Homo sapiens

PROVIDER: GSE68328 | GEO | 2016/03/22

SECONDARY ACCESSION(S): PRJNA282497

REPOSITORIES: GEO

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Project description:Genetically engineered human pluripotent stem cells (hPSCs) have been proposed as a source for transplantation therapies and are rapidly becoming valuable tools for human disease modeling. However, many of the potential applications are still limited by the lack of robust differentiation paradigms that allow for the isolation of defined functional tissues. These challenges could be overcome by the use of adult tissue stem cells derived from hPSCs, as their restricted potential could limit the differentiation towards other undesired linages, and allow in vitro expansion and long- term propagation of fully differentiated tissue. To isolate adult stem cells from hPSCs, we applied genome-editing to generate an LGR5-GFP reporter system and subsequently developed a differentiation protocol for human intestinal tissue comprising an adult stem cell niche and all major cell types of the adult intestine. This novel derivation protocol is highly robust and even permits the isolation of intestinal organoids without the LGR5 reporter. Transcriptional profiling, electron microscopy and functional analysis revealed that such human organoid cultures could be derived with high purity, and a composition and morphology similar to that of cultures obtained from human biopsies. Importantly, hPSC-derived organoids responded to the canonical signaling pathways that control self-renewal and differentiation in the adult human intestinal stem cell compartment. With our ability to genetically engineer hPSCs using site-specific nucleases, this adult stem cell system provides a novel platform by which to study human intestinal disease in vitro. RNA from primary organoid samples was isolated from organoid lines that were both cultured for 1-6 months and derived from duodenum, ileum, or rectum biopsies of human subjects as described previously (Sato et al., Gastroenterology 2011) grown in media called WENR+inhibitors. RNA was also isolated from various steps in the culturing and differentiation protocol.

Project description:Zinc finger nucleases (ZFN) are powerful tools for editing genes in cells. Here we use ZFNs to interrogate the biological function of human ADPGK, which encodes an ADP-dependent glucokinase (ADPGK), in tumour cell lines. The hypothesis tested is that ADPGK utilises ADP to phosphorylate glucose under conditions where ATP becomes limiting, such as hypoxia. We characterised two ZFN knockout clones in each of two tumour cell lines (H460 and HCT116). All four lines had frameshift mutations in all alleles at the target site in exon 1 of ADPGK, and were ADPGK-null by immunoblotting. ADPGK knockout had little or no effect on cell proliferation, but compromised the ability of H460 cells to survive siRNA silencing of hexokinase-2 under oxic conditions, with clonogenic survival falling from 21±3% for the parental line to 6.4±0.8% (p=0.002) and 4.3±0.8% (p=0.001) for the two knockouts. A similar increased sensitivity to clonogenic cell killing was observed under anoxia. No such changes were found when ADPGK was knocked out in HCT116 cells, for which the parental line was less sensitive than H460 to anoxia and to hexokinase-2 silencing. While knockout of ADPGK in HCT116 cells caused few changes in global gene expression, knockout of ADPGK in H460 cells caused notable up-regulation of mRNAs encoding cell adhesion proteins. Surprisingly, we could discern no effect on glycolysis as measured by glucose consumption or lactate formation under oxic or anoxic conditions, or extracellular acidification rate (Seahorse XF analyser) under oxic conditions in a variety of media. However, oxygen consumption rates were generally lower in the ADPGK knockouts, in some cases markedly so. Collectively, the results demonstrate that ADPGK can contribute to tumour cell survival under conditions of high glycolytic dependence, but the phenotype resulting from knockout of ADPGK is cell line dependent and appears to be unrelated to priming of glycolysis. Use Affymetrix microarrays to examine the effecs of knockout of the gene ADPGK using Zinc Finger nucleases in two cultured cell lines: (i) HCT116 cells (three wild type cultures compared to three ADPGK-knockout cultures), (ii) H460 cells (two wild type cultures compared to two ADPGK-knockout cultures). Ten microarrays in total.

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Low dose irradiation enhances gene targeting in human pluripotent stem cells

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