Efficient production of recombinant human adiponectin in egg white using genome edited chickens

Single-cell RNA sequencing reveals surface markers of primordial germ cells in chicken and zebra finch

Primordial germ cells (PGCs) in avian species exhibit unique developmental features, including the ability to migrate through the bloodstream and colonize the gonads, allowing their isolation at various developmental stages. Several methods have been developed for the isolation of avian PGCs, including density gradient centrifugation, size-dependent separation, and magnetic-activated cell sorting (MACS) or fluorescence-activated cell sorting (FACS) using a stage-specific embryonic antigen-1 (SSEA-1) antibody. However, these methods present limitations in terms of efficiency and applicability across development stages. In particular, the specificity of SSEA-1 decreases in later developmental stages. Furthermore, surface markers that can be utilized for isolating or utilizing PGCs are lacking for wild birds, including zebra finches, and endangered avian species. To address this, we used single-cell RNA sequencing (scRNA-seq) to uncover novel PGC-specific surface markers in chicken and zebra finch. We screened for genes that were primarily expressed in the PGC population within the gonadal cells. Analyses of gene expression patterns and levels based on scRNA-seq, coupled with validation by RT-PCR, identified NEGR1 and SLC34A2 as novel PGC-specific surface markers in chickens and ESYT3 in zebra finches. Notably, these newly identified genes exhibited sustained expression not only during later developmental stages but also in reproductive tissues.

Sustainable production of multimeric and functional recombinant human adiponectin using genome-edited chickens

BACKGROUND

Adiponectin (ADPN) plays a critical role in endocrine and cardiovascular functions, but traditional production methods, such as Escherichia coli and mammalian systems, have faced challenges in generating sufficiently active middle molecular weight (MMW) and high molecular weight (HMW) forms of recombinant human ADPN (hADPN). In our previous study, we proposed genome-edited chickens as an efficient platform for producing multimeric hADPN. However, the consistency of multimeric hADPN expression in this system across generations had not been further investigated.

RESULTS

In this study, subsequent generations of ovalbumin (OVA) ADPN knock-in chickens showed stable multimeric hADPN production, yielding ~ 26% HMW ADPN (0.59 mg/mL) per hen. Comparative analysis revealed that egg white (EW)-derived hADPN predominantly consisted of hexameric and HMW forms, similar to serum-derived hADPN. In contrast, hADPN obtained from human embryonic kidney (HEK) 293 and High-Five (Hi-5) cells also exhibited the presence of trimers, indicating variability across different production systems. Furthermore, transcriptional expression analysis of ADPN multimerization-associated endoplasmic reticulum chaperone genes (Ero1-Lα, DsbA-L, ERP44, and PDI) indicated upregulation in the oviduct magnum of ADPN KI hens, suggesting the chicken oviduct magnum as the optimal site for HMW ADPN production. Lastly, the functional analysis demonstrated that EW-derived hADPN significantly reduced lipid droplets and downregulated lipid accumulation-related genes (LOX-1, AT1R, FAS, and FABP4) in human umbilical vein endothelial cells (HUVECs).

CONCLUSION

In summary, stable and functional multimeric hADPN can be produced in genome-edited chickens even after generations. This highlights the potential of using chicken bioreactor for producing various high-value proteins.

Clonally derived chicken primordial germ cell lines maintain biological characteristics and proliferative potential in long-term culture

Chicken primordial germ cells (PGCs) are important cells with significant implications in preserving genetic resources, chicken breeding and production, and basic research on genetics and development. Currently, chicken PGCs can be cultured long-term in vitro to produce single-cell clones. However, systematic exploration of the cellular characteristics of these single-cell clonal lines has yet to be conducted. In this study, single-cell clonal lines were established from male and female PGCs of Rugao Yellow Chicken and Shouguang Black Chicken, respectively, using a micropipette-based method for single-cell isolation and culture. Analysis of glycogen granule staining, mRNA expression of pluripotency marker genes (POUV, SOX2, NANOG), germ cell marker genes (DAZL, CVH), and SSEA-1, EMA-1, SOX2, C-KIT, and CVH protein expression showed positive results, indicating that PGCs maintain normal cellular properties after single-cell cloning. Furthermore, tests on proliferation ability and gene expression levels in PGC single-cell clonal lines showed high expression of the pluripotency-related genes and TERT compared to control PGCs, and PGC single-cell clonal lines demonstrated higher proliferation ability. Finally, green fluorescent protein (GFP)-PGC single-cell clonal lines were established, and it was found that these single-cell clonal lines could still migrate into the gonads of recipients, suggesting their potential for germ-line transmission. This study systematically validated the normal cellular characteristics of PGC single-cell clonal lines, indicating that they could be applied in genetic modification research on chickens.

Lipofection with Lipofectamine™ 2000 in a heparin-free growth medium results in high transfection efficiency in chicken primordial germ cells

Primordial germ cells (PGCs) that can differentiate into gametes are used to produce genome-edited chickens. However, the transfection efficiency into PGCs is low in chickens; therefore, the yield efficiency of PGCs modified via genome editing is problematic. In this study, we improved transfection efficiency and achieved highly efficient genome editing in chicken PGCs. For transfection, we used lipofection, which is convenient for gene transfer. Chicken PGC cultures require adding heparin to support growth; however, heparin significantly reduces lipofection efficiency (p < 0.01). Heparin-induced lipofection efficiency was restored by adding protamine. Based on these results, we optimized gene transfer into chicken PGCs. Lipofectamine 2000 and our PGC medium were the most efficient transfection reagent and medium, respectively. Finally, based on established conditions, we compared the gene knock-out efficiencies of ovomucoid, a major egg allergen, and gene knock-in efficiencies at the ACTB locus. These results indicate that optimized lipofection is useful for CRISPR/Cas9-mediated knock-out and knock-in. Our findings may contribute to the generation of genome-edited chickens and stimulate research in various applications involving them.

Strategies for the Generation of Gene Modified Avian Models: Advancement in Avian Germline Transmission, Genome Editing, and Applications

Avian models are valuable for studies of development and reproduction and have important implications for food production. Rapid advances in genome-editing technologies have enabled the establishment of avian species as unique agricultural, industrial, disease-resistant, and pharmaceutical models. The direct introduction of genome-editing tools, such as the clustered regularly interspaced short palindromic repeats (CRISPR) system, into early embryos has been achieved in various animal taxa. However, in birds, the introduction of the CRISPR system into primordial germ cells (PGCs), a germline-competent stem cell, is considered a much more reliable approach for the development of genome-edited models. After genome editing, PGCs are transplanted into the embryo to establish germline chimera, which are crossed to produce genome-edited birds. In addition, various methods, including delivery by liposomal and viral vectors, have been employed for gene editing in vivo. Genome-edited birds have wide applications in bio-pharmaceutical production and as models for disease resistance and biological research. In conclusion, the application of the CRISPR system to avian PGCs is an efficient approach for the production of genome-edited birds and transgenic avian models.