Effect of leukemia inhibitory factor and forskolin on establishment of rat embryonic stem cell lines

Embryonic Stem Cells and Gene Manipulation in Rat

Transgenic technology in rats is increasingly important for the design and implementation of biological and physiological studies in the fields of neuroscience, pharmacology, and toxicology. Pluripotent embryonic stem cells (ESCs) are a useful tool for generation of gene-modified rats. During the last decade, not only foreign DNA introduction but also endogenous DNA modification has been successfully achieved with rat ESCs. Detailed protocols for establishment of bona fide rat ESCs and their use for production of gene-modified rats are described in this chapter.

Organ Generation from Knockedout Rat Blastocysts Complemented with Pluripotent Stem Cells

Regeneration of human organs in domestic animal model would provide enough number of functional donor organs in transplantation therapy. Recent progresses in pluripotent stem cells and nuclease-based genome editing tools have set the stage for investigating the chimeric complementation approach to generate functional organs from embryonic stem (ES) cells or induced pluripotent stem (iPS) cells. In this chapter, protocol for allogeneic or xenogeneic organ generation using knocked-out (KO) rat blastocysts and the rat or mouse ES/iPS cells is described. The protocol includes (1) the preparation of KO rat colony, (2) the preparation of rat or mouse ES/iPS cells, (3) the recovery of rat blastocysts, (4) the stem cell injection into blastocysts, (5) the embryo transfer into pseudopregnant recipient uteri, and (6) the genotyping and organogenetic analysis of chimeric offspring. The accumulation of basic and practical knowledge in the rodent model would be useful in improving therapeutic performance to regenerate 3D organs available for transplantation.

Gene Editing in Rat Embryonic Stem Cells to Produce In Vitro Models and In Vivo Reporters

Rat embryonic stem cells (ESCs) offer the potential for sophisticated genome engineering in this valuable biomedical model species. However, germline transmission has been rare following conventional homologous recombination and clonal selection. Here, we used the CRISPR/Cas9 system to target genomic mutations and insertions. We first evaluated utility for directed mutagenesis and recovered clones with biallelic deletions in Lef1. Mutant cells exhibited reduced sensitivity to glycogen synthase kinase 3 inhibition during self-renewal. We then generated a non-disruptive knockin of dsRed at the Sox10 locus. Two clones produced germline chimeras. Comparative expression of dsRed and SOX10 validated the fidelity of the reporter. To illustrate utility, live imaging of dsRed in neonatal brain slices was employed to visualize oligodendrocyte lineage cells for patch-clamp recording. Overall, these results show that CRISPR/Cas9 gene editing technology in germline-competent rat ESCs is enabling for in vitro studies and for generating genetically modified rats.

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Gene mutation and homologous recombination in rat ESCs using CRISPR/Cas9

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Lef1 mutants exhibit predicted loss of hypersensitivity to GSK3 inhibition

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Sox10 knockin rat provides a vital reporter of neural crest and oligodendroglia

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Sox10::dsRed facilitates patch-clamp recording from oligodendroglial lineage cells

Haploid embryonic stem cell lines derived from androgenetic and parthenogenetic rat blastocysts

The present study was conducted to establish haploid embryonic stem (ES) cell lines using fluorescent marker-carrying rats. In the first series, 7 ES cell lines were established from 26 androgenetic haploid blastocysts. However, only 1 ES cell line (ahES-2) was found to contain haploid cells (1n = 20 + X) by fluorescence-activated cell sorting (FACS) and karyotypic analyses. No chimeras were detected among the 10 fetuses and 41 offspring derived from blastocyst injection with the FACS-purified haploid cells. In the second series, 2 ES cell lines containing haploid cells (13% in phES-1 and 1% in phES-2) were established from 2 parthenogenetic haploid blastocysts. Only the phES-2 cell population was purified by repeated FACS to obtain 33% haploid cells. Following blastocyst injection with the FACS-purified haploid cells, no chimera was observed among the 11 fetuses; however, 1 chimeric male was found among the 47 offspring. Although haploid rat ES cell lines can be established from both blastocyst sources, FACS purification may be necessary for maintenance and chimera production.

CRISPR/Cas-mediated genome editing in the rat via direct injection of one-cell embryos

Conventional embryonic stem cell (ESC)-based gene targeting, zinc-finger nuclease (ZFN) and transcription activator-like effector nuclease (TALEN) technologies are powerful strategies for the generation of genetically modified animals. Recently, the CRISPR/Cas system has emerged as an efficient and convenient alternative to these approaches. We have used the CRISPR/Cas system to generate rat strains that carry mutations in multiple genes through direct injection of RNAs into one-cell embryos, demonstrating the high efficiency of Cas9-mediated gene editing in rats for simultaneous generation of compound gene mutant models. Here we describe a stepwise procedure for the generation of knockout and knock-in rats. This protocol provides guidelines for the selection of genomic targets, synthesis of guide RNAs, design and construction of homologous recombination (HR) template vectors, embryo microinjection, and detection of mutations and insertions in founders or their progeny. The procedure from target design to identification of founders can take as little as 6 weeks, of which <10 d is actual hands-on working time.