Electroporation-based Easi-CRISPR yields biallelic insertions of EGFP-HiBiT cassette in immortalized chicken oviduct epithelial cells.

Laying hens are an excellent experimental oviduct model for studying reproduction biology. Because chicken oviduct epithelial cells (cOECs) have a crucial role in synthesizing and secreting ovalbumin, laying hens have been regarded an ideal bioreactor for producing pharmaceuticals in egg white through transgene or gene editing of the ovalbumin (OVA) gene. However, related studies in cOECs are largely limited because of the lack of immortalized model cells. In addition, the editing efficiency of conventional CRISPR-HDR knock-in in chicken cells is suboptimal (ranging from 1 to 10%) and remains elevated. Here, primary cOECs were isolated from young laying hens, then infected with a retrovirus vector of human telomerase reverse transcriptase (hTERT), and immortalized cOECs were established. Subsequently, an electroporation-based Easi-CRISPR (Efficient additions with ssDNA inserts-CRISPR) method was adopted to integrate an EGFP-HiBiT cassette into the chicken OVA locus (immediately upstream of the stop codon). The immortalized cOECs reflected the self-renewal capability and phenotype of oviduct epithelial cells. This is because these cells not only maintained stable proliferation and normal karyotype and had no potential for malignant transformation, but also expressed oviduct markers and an epithelial marker and had a morphology similar to that of primary cOECs. EGFP expression was detected in the edited cells through microscopy, flow cytometry, and HiBiT/Western blotting. The EGFP-HiBiT knock-in efficiency reached 27.9% after a single round of electroporation, which was determined through genotyping and DNA sequencing. Two single cell clones contained biallelic insertions of EGFP-HiBiT donor cassettes. In conclusion, our established immortalized cOECs could act as an in vitro cell model for gene editing in chicken, and this electroporation-based Easi-CRISPR strategy will contribute to the generation of avian bioreactors and other gene-edited (GE) birds.

Electroporation of SUMO-His-Cre protein triggers a specific recombinase-mediated cassette exchange in HEK 293T cells.

Cre recombinase is a widely-used genetic manipulation of genomic DNA. However, the conventional transfection of the DNA vectors expressing the Cre recombinase or viral transduction method yields low transfection efficiencies or insertion mutagenesis. The present paper evaluated whether the direct protein delivery of Cre recombinase through electroporation can induce the Cre-mediated recombination in the HEK 293T cells. Here, the small ubiquitin-related modifier (SUMO) -tagged His-Cre fusion protein was expressed in a soluble pattern in the Eschrichria coli (E.coli) cells, purified using affinity chromatography, and finally electroporated into the HEK 293T cells. These cells were previously transfected with three different Cre reporter vectors. The electroporation of the HEK 293T cells revealed either the activation of EGFP expression, or a decrease in RFP expression, and a concomitant increase in EGFP expression, indicating a desired recombinase-mediated cassette exchange (RMCE) event (conversion of RFP to EGFP), and a biological activity of the purified SUMO-His-Cre protein. The fusion protein is expected to serve in the Easi-CRISPR-LoxP-mediated genome editing to generate transgenic animal models.

Specificity and application of SOX2 antibody.

Sox2 is known to play an important role in maintaining the totipotency and self-renewal of embryonic stem cells. The purpose of this study was to prepare an anti-chicken Sox2 polyclonal antibody using prokaryotic expression techniques, to evaluate its specificity and to use it to investigate the expression and distribution of Sox2 in the chicken brain and lungs. The chicken Sox2 gene was amplified and subcloned to a pET-30a vector to construct a prokaryotic expression vector, pET-Sox2. A His-Sox2 fusion protein was expressed, purified, and used to prepare an antichicken Sox2 polyclonal antibody. Western blotting revealed that the antichicken Sox2 antibody could specifically bind not only to the purified His-Sox2 fusion protein but also to the endogenous Sox2 protein in the testes of chicken, showing a distinct dose-dependent relationship between antigen and Sox2 antibody. Indirect immunofluorescent staining of Sox2-overexpressing cells showed strong nuclear and diffuse cytoplasmic immunoreactivity for Sox2 in the antichicken Sox2 antibody-staining cells. A CRISPR/Cas9 effector system-mediated Sox2 knockdown assay indicated that Sox2 expression in HEK 293T cells was downregulated in the presence of doxycycline but upregulated in the absence of doxycycline. In addition, cryosectioning and immunohistochemical staining illustrated that most spermatogonia in the seminiferous tubules, and a small number of Sertoli and Leydig cells, were positive for Sox2. The antichicken Sox2 antibody was also successfully used to investigate the expression and distribution of Sox2 in the chicken cerebellar cortex, optic tectum, cerebral cortex, and lungs. The results of this study confirmed the specificity of the antichicken Sox2 polyclonal antibody, which will be available for the study of biological functions of the chicken Sox2 gene and the self-renewal mechanisms of chicken pluripotent stem cells.

Investigation of the effects of dichlorvos poisoning on AMPK signaling pathway in chicken brain tissues.

Dichlorvos is a common crop insecticide widely used by people which causes extensive and serious environmental pollution. However, it has been shown that organophosphorus poisoning causes energy metabolism and neural disorders. The overall purpose of this study was to investigate the damage to brain tissue and the changes in AMPK signaling pathway-related gene expression after dichlorvos poisoning in chickens. White-feathered broiler chickens, as the research subjects of this experiment, were divided into three groups: control group, low-dose group (77.5% dichlorvos at 1.13 mg/kg dose) and high-dose group (77.5% dichlorvos at 10.2 mg/kg dose). Clinical symptoms were observed after modeling, and an integrative analysis was conducted using HE staining microscopy, immune-histochemical microscopy, electron microscopy and PCR arrays. The results showed that the high-dose group had more obvious dyspnea, salivation, convulsion and other neurological phenomena. Pathological sections showed that nuclear disintegration of neurons was most obvious in the low-dose group, and apoptosis of brain cells was most obvious in the high-dose group, and the mitochondrial structure was destroyed in the two poisoned group, i.e. low-dose group and high-dose group. PCR arrays showed that AMPK signaling pathway was inhibited and the expressions of genes involved in energy metabolism (ACACA and PRKAA1) were significantly changed. Furthermore, genes associated with protein synthesis (EIF4EBP1) were significantly upregulated. FASN and HMGCR expressions were significantly increased. There were significant changes in the expressions of cell cycle-related genes (STK11, TP53 and FOXO3). Organophosphate poisoning can cause a lot of nuclear disintegration of brain neurons, increases cell apoptosis, disrupts the energy metabolism of mitochondrial structure, and inhibits the AMPK signaling pathway. These results provide a certain idea and basis for studying the mechanism of AMPK signaling after organophosphorus poisoning and provide a research basis for the prevention and treatment of organophosphorus poisoning.