Development and characterization of a CRISPR/Cas9-mediated RAG1 knockout chicken model lacking mature B and T cells

Fecal microbiota transplantation combined with inulin promotes the development and function of early immune organs in chicks

Modern management of chicks hinders the vertical transmission of intestinal microbiota, which is closely related to immunity. Inulin is a substrate that can be utilized by the microbiota. This study aimed to determine whether fecal microbiota transplantation (FMT) combined with inulin played a "1 + 1 > 2" role in enhancing the development and function of immune organs. Chicks were treated with 1 % inulin and/or fecal microbiota suspension on days 1-6. The growth performance, immune organ development, and immune indicators were evaluated on days 7, 14, and 21. Results showed that the combination of FMT and inulin significantly increased the immune organ index on day 7 and promoted the morphological structure and the expression of proliferating cell nuclear antigen (PCNA) in immune organs on days 7, 14, and 21. Each treatment increased the gene expression of interferon-gamma (IFN-γ), interleukin-4 (IL-4), interleukin-2 (IL-2), B cell-activating factor receptor (BAFFR), B cell linker (BLNK), C-X-C Motif Chemokine Ligand 12 (CXCL12), C-X-C Motif Chemokine Receptor 4 (CXCR4), and Biotin (Bu-1) to varying degrees. FMT combined with inulin significantly increased the expression of IgA-positive cells on days 7 and 14. In conclusion, the synergistic effect of FMT and inulin had beneficial impacts on the development and function of immune organs.

Avian Models for Human Carcinogenesis-Recent Findings from Molecular and Clinical Research

Birds, especially the chick and hen, have been important biomedical research models for centuries due to the accessibility of the avian embryo and the early discovery of avian viruses. Comprehension of avian tumor virology was a milestone in basic cancer research, as was that of non-viral genesis, as it enabled the discovery of oncogenes. Furthermore, studies on avian viruses provided initial insights into Kaposi's sarcoma and EBV-induced diseases. However, the role of birds in human carcinogenesis extends beyond the realm of virology research. Utilization of CAM, the chorioallantoic membrane, an easily accessible extraembryonic tissue with rich vasculature, has enabled studies on tumor-induced angiogenesis and metastasis and the efficient screening of potential anti-cancer compounds. Also, the chick embryo alone is an effective preclinical in vivo patient-derived xenograft model, which is important for the development of personalized therapies. Furthermore, adult birds may also closely resemble human oncogenesis, as evidenced by the laying hen, which is the only animal model of a spontaneous form of ovarian cancer. Avian models may create an interesting alternative compared with mammalian models, enabling the creation of a relatively cost-effective and easy-to-maintain platform to address key questions in cancer biology.

Characterization and ontogeny of a novel lymphoid follicle inducer cell during development of the bursa of Fabricius

The avian bursa of Fabricius (BF) is a primary lymphoid organ, where B-cell development occurs within bursal follicles of epithelial origin. During embryogenesis the epithelial anlage of the BF emerges as a diverticulum of the cloaca surrounded by undifferentiated tail bud mesenchyme. While it is believed that the epithelial-mesenchymal BF primordium provides a selective microenvironment for developing B cells, the initial events inducing lymphoid follicle formation are not fully elucidated. Using wild type and CSF1R-eGFP transgenic chick embryos, we find that separate B cell, macrophage and dendritic cell precursors enter the BF mesenchyme, migrate to the surface epithelium, and colonize the lymphoid follicle buds. Detailed immunocytochemical characterization revealed a novel EIV-E12+ blood-borne cell type, colonizing the surface epithelium of the BF rudiment before the entry of myeloid and lymphoid lineages and the appearance of this cell type coincides with the onset of follicle bud formation. Chick-duck chimeras and chick-quail tissue recombination experiments suggest that EIV-E12+ cells represent a transient lymphoid inducer cell population. They are not dendritic or B cells precursors, and they are capable of follicle bud induction in both dendritic cell- and B cell-depleted bursae.

Comparative study of PGCs cultivation systems HiS and FAcs: a transcriptomic and cellular biology perspective

In chicken, primordial germ cells (PGC) are crucial for the preservation and manipulation of genetic resources in poultry production. The HiS and FAcs culture systems are two important methods for the in vitro cultivation of chicken PGCs. The purpose of this study was to compare and analyze the two cultivation systems for PGCs (His and FAcs culture systems) to assess their efficacy and applicability in supporting PGC growth, maintaining PGC characteristics, and lineage transmission ability. The study found that both HiS and FAcs culture systems could maintain the basic biological characteristics of chicken PGCs, including the simultaneous expression of pluripotency and reproductive marker genes, as well as the presence of abundant glycogen granules. Subsequently, we identified 2,145 differentially expressed genes (DEG) through RNA sequencing. GO and KEGG analysis revealed a large number of DEGs enriched in the cell adhesion and calcium ion binding pathways, and the analysis found that these genes maintained a higher level in HiS-PGCs. Further personalized analysis found that the regulatory genes for maintaining PGC pluripotency were highly expressed in HiS-PGCs, while germ cell-related genes showed similar expression in both systems. Additionally, through RNA sequencing data and cell proliferation ability, it was found that PGCs in the FAcs system had a higher proliferation rate and a faster cell cycle. Finally, it was discovered that the expression of cell migration-related genes was maintained at a higher level in HiS-PGCs, but the migration efficiency of HiS-PGCs did not show a significant difference compared to FAcs-PGCs. These results suggest that both HiS and FAcs culture systems can maintain the proliferation and basic characteristics of chicken PGCs, but differences exist in cell proliferation, pluripotency regulation, and cell adhesion. These findings provide new information for optimizing PGC cultivation systems and are important for the preservation and genetic improvement of chicken PGCs.

Advancement of animal and poultry nutrition: Harnessing the power of CRISPR-Cas genome editing technology

CRISPR-associated proteins and clustered regularly interspaced short palindromic repeats (CRISPR-Cas) technology has emerged as a groundbreaking advancement in animal and poultry nutrition to improve feed conversion efficiency, enhance disease resistance, and improve the nutritional quality of animal products. Despite significant advancements, there is a research gap in the systematic understanding and comprehensive use of the CRISPR-Cas method in animal and poultry nutrition. The purpose of this study is to elucidate the latest advancements in animal and poultry nutrition through CRISPR-Cas genome editing technology, focusing on gene manipulation in metabolism, immunity, and growth. Following preferred reporting items in meta-analysis and systematic reviews guidelines, we conducted a systematic search using several databases, including Scopus, PubMed, and Web of Science, until May 2024, and finally, we included a total of 108 articles in this study. This article explores the use of the CRISPR-Cas system in the advancement of feed additives like probiotics and enzymes, which could reduce the use of antibiotics in animal production. Furthermore, the article discusses ethical and regulatory issues related to gene editing in animal and poultry nutrition, including concerns about animal welfare, food safety, and environmental impacts. Overall, the CRISPR-Cas system holds substantial promise to overcome the challenges in modern animal agriculture. By enriching the nutritional quality of animal products, increasing disease resistance, and improving feed efficiency, it offers sustainable and cost-effective solutions that can revolutionize animal and poultry nutrition.

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.

The Immunological Basis for Vaccination

Vaccination is crucial for health protection of poultry and therefore important to maintaining high production standards. Proper vaccination requires knowledge of the key players of the well-orchestrated immune system of birds, their interdependence and delicate regulation, and, subsequently, possible modes of stimulation through vaccine antigens and adjuvants. The knowledge about the innate and acquired immune systems of birds has increased significantly during the recent years but open questions remain and have to be elucidated further. Despite similarities between avian and mammalian species in their composition of immune cells and modes of activation, important differences exist, including differences in the innate, but also humoral and cell-mediated immunity with respect to, for example, signaling transduction pathways, antigen presentation, and cell repertoires. For a successful vaccination strategy in birds it always has to be considered that genotype and age of the birds at the time point of immunization as well as their microbiota composition may have an impact and may drive the immune reactions into different directions. Recent achievements in the understanding of the concept of trained immunity will contribute to the advancement of current vaccine types helping to improve protection beyond the specificity of an antigen-driven immune response. The fast developments in new omics technologies will provide insights into protective B- and T-cell epitopes involved in cross-protection, which subsequently will lead to the improvement of vaccine efficacy in poultry.

Loss of αβ but not γδ T cells in chickens causes a severe phenotype

The availability of genetically modified mice has facilitated the study of mammalian T cells. No model has yet been developed to study these cells in chickens, an important livestock species with a high availability of γδ T cells. To investigate the role of γδ and αβ T cell populations in birds, we generated chickens lacking these T cell populations. This was achieved by genomic deletion of the constant region of the T cell receptor γ or β chain, leading to a complete loss of either γδ or αβ T cells. Our results show that a deletion of αβ T cells but not γδ T cells resulted in a severe phenotype in KO chickens. The αβ T cell KO chickens exhibited granulomas associated with inflammation of the spleen and the proventriculus. Immunophenotyping of αβ T cell KO chickens revealed a significant increase in monocytes and expectedly the absence of CD4+ T cells including FoxP3+ regulatory T cells. Surprisingly there was no increase of γδ T cells. In addition, we observed a significant decrease in immunoglobulins, B lymphocytes, and changes in the bursa morphology. Our data reveal the consequences of T cell knockouts in chickens and provide new insights into their function in vertebrates.

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.