发布: 2018年04月05日第8卷第7期 DOI: 10.21769/BioProtoc.2794 浏览次数: 11318
评审: David CisnerosSara E HowdenGanesh Swaminathan
Abstract
For both disease and basic science research, loss-of-function (LOF) mutations are vitally important. Herein, we provide a simple stream-lined protocol for generating LOF iPSC lines that circumvents the technical challenges of traditional gene-editing and cloning of established iPSC lines by combining the introduction of the CRISPR vector concurrently with episomal reprogramming plasmids into fibroblasts. Our experiments have produced nearly even numbers of all 3 genotypes in autosomal genes. In addition, we provide a detailed approach for maintaining and genotyping 96-well plates of iPSC clones.
Keywords: Induced pluripotent stem cells (诱导的多能干细胞)Background
CRISPR/Cas9 technology has allowed easy and specific targeting of a particular genomic location for gene-editing. Combining this technology with the disease modeling and regenerative medicine potential of induced pluripotent stem cells (iPSCs) will continue to have unprecedented impacts on biomedical research. However, adapting the CRISPR/Cas9 system to iPSCs has presented several challenges. The traditional approach for gene-editing in cell lines is to transfect the cells with a plasmid expressing the Cas9 protein and guide RNA (gRNA) after which single clones are generated and screened for the desired genetic alteration. Unfortunately, iPSCs are not amenable to single cell cloning. Several media supplements and cloning approaches have been developed to overcome this difficulty but are still fraught with either expensive equipment (low oxygen incubators), difficult technological steps (survival of FACS sorted single iPSCs), or labor intensive protocols (sub-cloning) (Forsyth et al., 2006; Miyaoka et al., 2014). Moreover, single cell passaging has been linked to increased genomic abnormalities in iPSCs (Bai et al., 2015). Fluorescent or antibiotic resistance genetic markers have been used to overcome issues with clonality and the overall low efficiency of gene-editing in these cells, but require homologous recombination of a large cassette via a targeting plasmid designed with long homology arms (400-800 bp) (Hendel et al., 2014). Designing these plasmids takes a great deal of time.
To overcome many of these obstacles, we utilized a combined approach of simultaneous reprogramming and CRISPR/Cas9 mutagenesis to generate both heterozygous and homozygous loss-of-function (LOF) iPSC lines. This combined approach was first presented by Howden and colleagues for homologous recombination gene-editing (Howden et al., 2015 and 2016), but we have expanded upon and further defined their original results for indel formation in a recent publication (Tidball et al., 2017). This procedure takes advantage of the cloning step inherent to iPSC reprogramming as well as the greater ease of transfection in fibroblast culture (Figure 1). The ability to efficiently generate a large number of clones with a similar proportion of all three genotypes (wild-type/wild-type, wild-type/indel, and indel/indel) will allow rapid development of LOF iPSC lines for disease modeling and basic research.
Figure 1. Overview of the experimental workflow. The protocols in this article are broken into 4 major sections, including: guide RNA and PCR primer design (Step 1), CRISPR plasmid generation and purification (Steps 2-6), fibroblast culture and electroporation with CRISPR and reprogramming plasmids (Steps 7-8), and isolating genomic DNA followed by PCR of the targeted region and sequencing (Steps 11-15).
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文章信息
版权信息
© 2018 The Authors; exclusive licensee Bio-protocol LLC.
如何引用
Tidball, A. M., Swaminathan, P., Dang, L. T. and Parent, J. M. (2018). Generating Loss-of-function iPSC Lines with Combined CRISPR Indel Formation and Reprogramming from Human Fibroblasts. Bio-protocol 8(7): e2794. DOI: 10.21769/BioProtoc.2794.
分类
干细胞 > 多能干细胞 > 细胞诱导
细胞生物学 > 细胞工程 > CRISPR-cas9
分子生物学 > DNA > 诱/突变
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