production-apolipoprotein-c-iii-knockout-rabbits-using-zinc-finger

Production of Apolipoprotein C-III Knockout Rabbits using Zinc Finger Nucleases

Apolipoprotein (Apo) C-III (ApoCIII) resides on the surface of plasma chylomicron (CM), very low density lipoprotein (VLDL) and high density lipoproteins ...

crisprcas9-ribonucleoprotein-mediated-precise-gene-editing-tube

CRISPR/Cas9 Ribonucleoprotein-mediated Precise Gene Editing by Tube Electroporation

Gene editing nucleases, represented by CRISPR-associated protein 9 (Cas9), are becoming mainstream tools in biomedical research. Successful delivery of ...

University of Michigan Medical Center

Reprogramming impairment of DNA methylation may be partly responsible for the low efficiency in somatic cell nuclear transfer. In this study, bovine fibroblast cells were transfected with enhancer green fluorescence protein (eGFP), and then treated with a histone-deacetylase inhibitor, trichostatin A (TSA). The results showed that the effect of TSA on transfected cells was dose dependent. When the TSA concentration was over 5 ng/ml, cell proliferation was significantly inhibited. The majority of the cells died when TSA reached 100 ng/ml (P < 0.01). The number of cells in the S phase was significantly decreased in the 5- to 50-ng/ml TSA-treated groups, while the majority of the cells were at the G0/G1 phases. The number of eGFP-expressed cells were approximately twofold higher in 25-ng/ml (30.5%) and 50-ng/ml (29.5%) TSA groups than the control (15.0%). Reduced DNA methylation and improved histone acetylation were observed when the cells were treated with 10 to 50 ng/ml of TSA. Transfer of the TSA-treated cells to enucleated recipient oocytes resulted in similar cleavage rates among the experimental groups and the control. Cells treated with 50 ng/ml of TSA resulted in significantly lower blastocyst development (9.9%) than the other experimental and the control groups (around 20%). Analysis of the putative blastocysts showed that 86.7% of the embryos derived from TSA-treated cells were eGFP positive, which was higher than that from untreated cells (68.8%). In conclusion, treatment of transfected cells with TSA decreased the genome DNA methylation level, increased histone acetylation, and eGFP gene expression was activated. Donor cells with reduced DNA methylation did not improve subsequent cloned embryo development; however, transgene expression was improved in cloned embryos.

Trichostatin A improved epigenetic modifications of transfected cells but did not improve subsequent cloned embryo development.

In the present study, cashmere goat fetal fibroblasts were transfected with pCDsR-KI, a hair-follicle-cell specific expression vector for insulin-like growth factor 1 (IGF1) that contains two markers for selection (red fluorescent protein gene and neomycin resistant gene). The transgenic fibroblasts cell lines were obtained after G418 selection. Prior to the somatic cell nuclear transfer (SCNT), the maturation rate of caprine cumulus oocytes complexes (COCs) was optimized to an in vitro maturation time of 18 h. Parthenogenetic ooctyes were used as a model to investigate the effect of two activation methods, one with calcium ionophore IA23187 plus 6-DMAP and the other with ethanol plus 6-DMAP. The cleavage rates after 48 h were respectively 88.7% and 86.4%, with no significant difference (P>0.05). There was no significant difference between the cleavage rate and the blastocyst rate in two different media (SO-Faa and CR1aa; 86.3% vs 83.9%, P>0.05 and 23.1% vs 17.2%, P>0.05). The fusion rate of a 190 V/mm group (62.4%) was significantly higher than 130 V/mm (32.8%) and 200 V/mm (42.9%), groups (P>0.05). After transgenic somatic cell nuclear transfer (TSCNT) manipulation, 203 reconstructed embryos were obtained in which the cleavage rate after in vitro development (IVD) for 48 h was 79.3% (161/203). The blastocyst rate after IVD for 7 to 9 d was 15.3% (31/203). There were 17 embryos out of 31 strongly expressing red fluorescence. Two of the red fluorescent blastocysts were randomly selected to identify transgene by polymerase chain reaction. Both were positive. These results showed that: (i) RFP and Neo ( r ) genes were correctly expressed indicating that transgenic somatic cell lines and positive transgenic embryos were obtained; (ii) one more selection at the blastocyst stage was necessary although the donor cells were transgenic positive, because only partially transgenic embryos expressing red fluorescence were obtained; and (iii) through TSCNT manipulation and optimization, transgenic cashmere goat embryos expressing red fluorescence and containing an IGF1 expression cassette were obtained, which was sufficient for production of transgenic cashmere goats.

Production of transgenic cashmere goat embryos expressing red fluorescent protein and containing IGF1 hair-follicle-cell specific expression cassette by somatic cell nuclear transfer.

Generation of induced pluripotent stem cells from somatic cells using defined factors has potential relevant applications in regenerative medicine and biology. However, this promising technology remains inefficient and time consuming. We have devised a serum free culture medium termed iSF1 that facilitates the generation of mouse induced pluripotent stem cells. This optimization of the culture medium is sensitive to the presence of Myc in the reprogramming factors. Moreover, we could reprogram meningeal cells using only two factors Oct4/Klf4. Therefore, iSF1 represents a basal medium that may be used for mechanistic studies and testing new reprogramming approaches.

Towards an optimized culture medium for the generation of mouse induced pluripotent stem cells.

Epithelial-to-mesenchymal transition (EMT) is a developmental process important for cell fate determination. Fibroblasts, a product of EMT, can be reset into induced pluripotent stem cells (iPSCs) via exogenous transcription factors but the underlying mechanism is unclear. Here we show that the generation of iPSCs from mouse fibroblasts requires a mesenchymal-to-epithelial transition (MET) orchestrated by suppressing pro-EMT signals from the culture medium and activating an epithelial program inside the cells. At the transcriptional level, Sox2/Oct4 suppress the EMT mediator Snail, c-Myc downregulates TGF-beta1 and TGF-beta receptor 2, and Klf4 induces epithelial genes including E-cadherin. Blocking MET impairs the reprogramming of fibroblasts whereas preventing EMT in epithelial cells cultured with serum can produce iPSCs without Klf4 and c-Myc. Our work not only establishes MET as a key cellular mechanism toward induced pluripotency, but also demonstrates iPSC generation as a cooperative process between the defined factors and the extracellular milieu. PAPERCLIP:

A mesenchymal-to-epithelial transition initiates and is required for the nuclear reprogramming of mouse fibroblasts.

Neurodegeneration is a hallmark of many neurological diseases, including Alzheimer's, Parkinson's and the polyglutamine diseases, which are all caused by misfolded proteins that accumulate in neuronal cells of the brain. Although apoptosis is believed to contribute to neurodegeneration in these cases, genetic mouse models of these diseases often fail to replicate apoptosis and overt neurodegeneration in the brain. Using nuclear transfer, we generated transgenic Huntington's disease (HD) pigs that express N-terminal (208 amino acids) mutant huntingtin with an expanded polyglutamine tract (105Q). Postnatal death, dyskinesia and chorea-like movement were observed in some transgenic pigs that express mutant huntingtin. Importantly, the transgenic HD pigs, unlike mice expressing the same transgene, displayed typical apoptotic neurons with DNA fragmentation in their brains. Also, expression of mutant huntingtin resulted in more neurons with activated caspase-3 in transgenic pig brains than that in transgenic mouse brains. Our findings suggest that species differences determine neuropathology and underscore the importance of large mammalian animals for modeling neurological disorders.

Expression of Huntington's disease protein results in apoptotic neurons in the brains of cloned transgenic pigs.

Porcine pluripotent cells with the capacity to generate germ line chimeras have not been developed yet. The transcription factor Oct-4 is an important marker of undifferentiating status and a central regulator of pluripotency in cells. Establishment of an Oct-4 promoter-based reporter system, such as that used in mice, will be a useful tool for monitoring the differentiating statuses of porcine cells both in vivo and in vitro. In the present study, we constructed a vector, pOGN2, in which enhanced green fluorescent protein (EGFP) was driven by the porcine Oct-4 promoter. In pigs containing this vector, EGFP was expected to be specifically expressed in pluripotent cells. We delivered the vectors into porcine fetal fibroblasts (PEFs) using liposomes. After transfected PEFs were selected with G418, we established eight cell lines containing the pOGN2 vector. When transgenic cells were used as donor nuclei to make somatic cell nuclear transfer (SCNT) embryos, SCNT embryos derived from four transgenic cell lines expressed green fluorescence. When PEFs with pOGN2 vectors were infected with retroviral vectors encoding the four transcription factors (Oct-4, Sox2, Klf4, and c-Myc), EGFP-expressing iPS cell colonies were observed at day 20. This work lays a foundation that can be used to generate a pig strain with an Oct4-EGFP reporter system, which would be greatly helpful in studying the differentiating and reprogramming mechanisms of pig embryos.

Establishment of a porcine Oct-4 promoter-driven EGFP reporter system for monitoring pluripotency of porcine stem cells.

Generation of PPARγ mono-allelic knockout pigs via zinc-finger nucleases and nuclear transfer cloning.

Multiple genetic modifications in pigs can essentially benefit research on agriculture, human disease and xenotransplantation. Most multi-transgenic pigs have been produced by complex and time-consuming breeding programs using multiple single-transgenic pigs. This study explored the feasibility of producing multi-transgenic pigs using the viral 2A peptide in the light of previous research indicating that it can be utilized for multi-gene transfer in gene therapy and somatic cell reprogramming. A 2A peptide-based double-promoter expression vector that mediated the expression of four fluorescent proteins was constructed and transfected into primary porcine fetal fibroblasts. Cell colonies (54.3%) formed under G418 selection co-expressed the four fluorescent proteins at uniformly high levels. The reconstructed embryos, which were obtained by somatic cell nuclear transfer and confirmed to express the four fluorescent proteins evenly, were transplanted into seven recipient gilts. Eleven piglets were delivered by two gilts, and seven of them co-expressed the four fluorescent proteins at equivalently high levels in various tissues. The fluorescence intensities were directly observed at the nose, hoof and tongue using goggles. The results suggest that the strategy of combining the 2A peptide and double promoters efficiently mediates the co-expression of the four fluorescent proteins in pigs and is hence a promising methodology to generate multi-transgenic pigs by a single nuclear transfer.

Use of the 2A peptide for generation of multi-transgenic pigs through a single round of nuclear transfer.

Piglets cloned from induced pluripotent stem cells.

Using the CRISPR/Cas9 gene-editing technology, we recently produced a number of rabbits with mutations in immune function genes, including FOXN1, PRKDC, RAG1, RAG2, and IL2RG. Seven founder knockout rabbits (F0) and three male IL2RG null (-/y) F1 animals demonstrated severe combined immunodeficiency (SCID), characterized by absence or pronounced hypoplasia of the thymus and splenic white pulp, and absence of immature and mature T and B-lymphocytes in peripheral blood. Complete blood count analysis showed severe leukopenia and lymphocytopenia accompanied by severe neutrophilia. Without prophylactic antibiotics, the SCID rabbits universally succumbed to lung infections following weaning. Pathology examination revealed severe heterophilic bronchopneumonia caused by  in several animals, but a consistent feature of lung lesions in all animals was a severe interstitial pneumonia caused by , as confirmed by histological examination and PCR analysis of  genes. The results of this study suggest that these SCID rabbits could serve as a useful model for human SCID to investigate the disease pathogenesis and the development of gene and drug therapies.

Bacterial and  Infections in the Lungs of Gene-Knockout Rabbits with Severe Combined Immunodeficiency.

Due to the lack of germline transmitting pluripotent stem cells (PSCs) cell lines and the extreme difficulty of somatic cell nuclear transfer (SCNT) in rabbit, the gene targeting technology in rabbit was lagging far behind those in rodents and in farm animals. As a result, the development and application of genetically engineered rabbit model are much limited. With the advent of gene editing nucleases, including ZFN, TALEN, and CRISPR/Cas9, it is now possible to produce gene targeting (i.e., knockout, knockin) rabbits with high success rates. In this chapter, we describe a comprehensive, step-by-step protocol for rabbit genome editing based on gene editing nucleases with specific emphasis of CRISPR/Cas9.

Generation of Rabbit Models by Gene Editing Nucleases.

Cystic fibrosis (CF) is a lethal autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Nuclease-mediated precise gene editing (PGE) represents a promising therapy for CF, for which an efficient strategy that is free of viral vector, drug selection, and reporter enrichment (VDR free) is desirable. Here we compared different transfection methods (lipofectamine versus electroporation) and formats (plasmid DNA versus ribonucleoprotein) in delivering the CRISPR/Cas9 elements along with single-stranded oligodeoxynucleotides (ssODNs) to clinically relevant cells targeting major CFTR mutation loci. We demonstrate that, among different combinations, electroporation of CRISPR/Cas9 and guide RNA (gRNA) ribonucleoprotein (Cas9 RNP) is the most effective one. By using this VDR-free method, 4.8% to 27.2% efficiencies were achieved in creating dF508, G542X, and G551D mutations in a wild-type induced pluripotent stem cell (iPSC) line. When it is applied to a patient-derived iPSC line carrying the dF508 mutation, a greater than 20% precise correction rate was achieved. As expected, genetic correction leads to the restoration of CFTR function in iPSC-derived proximal lung organoids, as well as in a patient-derived adenocarcinoma cell line CFPAC-1. The present work demonstrates the feasibility of gene editing-based therapeutics toward monogenic diseases such as CF.

Article Total : 2	Year
Publication title	2013
Publication title	2019

Article	Year
Trichostatin A improved epigenetic modifications of transfected cells but did not improve subsequent cloned embryo development. Animal biotechnology\| PubMed ID: 18855246	2008
Production of transgenic cashmere goat embryos expressing red fluorescent protein and containing IGF1 hair-follicle-cell specific expression cassette by somatic cell nuclear transfer. Science in China. Series C, Life sciences / Chinese Academy of Sciences\| PubMed ID: 19381465	2009
Towards an optimized culture medium for the generation of mouse induced pluripotent stem cells. The Journal of biological chemistry\| PubMed ID: 20595395	2010
A mesenchymal-to-epithelial transition initiates and is required for the nuclear reprogramming of mouse fibroblasts. Cell stem cell\| PubMed ID: 20621050	2010
Expression of Huntington's disease protein results in apoptotic neurons in the brains of cloned transgenic pigs. Human molecular genetics\| PubMed ID: 20660116	2010
Establishment of a porcine Oct-4 promoter-driven EGFP reporter system for monitoring pluripotency of porcine stem cells. Cellular reprogramming\| PubMed ID: 21254851	2011
Generation of PPARγ mono-allelic knockout pigs via zinc-finger nucleases and nuclear transfer cloning. Cell research\| PubMed ID: 21502977	2011
Use of the 2A peptide for generation of multi-transgenic pigs through a single round of nuclear transfer. PloS one\| PubMed ID: 21603633	2011
Piglets cloned from induced pluripotent stem cells. Cell research\| PubMed ID: 23247628	2013
Bacterial and Infections in the Lungs of Gene-Knockout Rabbits with Severe Combined Immunodeficiency. Frontiers in immunology\| PubMed ID: 29593714	2018
Generation of Rabbit Models by Gene Editing Nucleases. Methods in molecular biology (Clifton, N.J.)\| PubMed ID: 30353523	2019
Efficient Gene Editing at Major CFTR Mutation Loci. Molecular therapy. Nucleic acids\| PubMed ID: 30852378	2019

Dongshan Yang

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