Production of transgenic broilers by non-viral vectors via optimizing egg windowing and screening transgenic roosters

The science of genetically modified poultry

The exuberant development of targeted genome editing has revolutionized research on the chicken genome, generating chickens with beneficial parameters. The chicken model is a crucial experimental tool that can be utilized for drug manufacture, preclinical research, pathological observation, and other applications. In essence, tweaking the chicken’s genome has enabled the poultry industry to get more done with less, generating genetically modified chickens that lay eggs containing large amounts of lifesaving humanized drugs. The transition of gene editing from concept to practical application has been dramatically hastened by the development of programmable nucleases, bringing scientists closer than ever to the efficient producers of tomorrow’s medicines. Combining the developmental and physiological characteristics of the chicken with cutting-edge genome editing, the chicken furnishes a potent frontier that is foreseen to be actively pursued in the future. Herein we review the current and future prospects of gene editing in chickens and the contributions to the development of humanized pharmaceuticals.

Sequential verification of exogenous protein production in OVA gene-targeted chicken bioreactors

The chicken has potential as an efficient bioreactor system because of its outstanding protein production capacity and low cost. The CRISPR/Cas9-mediated gene-editing system enables production of highly marketable exogenous proteins in transgenic chicken bioreactors. However, because it takes approximately 18 mo to evaluate the recombinant protein productivity of the bioreactor due to the generation interval from G0 founders to G1 egg-laying hens, to verification of the exogenous protein at the early stage is difficult. Here we propose a system for sequential validation of exogenous protein production in chicken bioreactors as in hatching female chicks as well as in egg-laying hens. We generated chicken OVALBUMIN (OVA) EGFP knock-in (KI) chicken (OVA EGFP KI) by CRISPR/Cas9-mediated nonhomologous end joining at the chicken OVA gene locus. Subsequently, the estrogen analog, diethylstilbestrol (DES), was subcutaneously implanted in the abdominal region of 1-wk-old OVA EGFP KI female chicks to artificially increase OVALBUMIN expression. The oviducts of DES-treated OVA EGFP KI female chicks expressed OVA and EGFP at the 3-wk-old stage (10 d after DES treatment). We evaluated the expression of EGFP protein in the oviduct, along with the physical properties of eggs and egg white from OVA EGFP KI hens. The rapid identification and isolation of exogenous protein can be confirmed at a very early stage and high-yield production is possible by targeting the chicken oviduct.

Common Gene Modules Identified for Chicken Adiposity by Network Construction and Comparison

Excessive fat deposition can cause chicken health problem, and affect production efficiency by causing great economic losses to the industry. However, the molecular underpinnings of the complex adiposity trait remain elusive. In the current study, we constructed and compared the gene co-expression networks on four transcriptome profiling datasets, from two chicken lines under divergent selection for abdominal fat contents, in an attempt to dissect network compositions underlying adipose tissue growth and development. After functional enrichment analysis, nine network modules important to adipogenesis were discovered to be involved in lipid metabolism, PPAR and insulin signaling pathways, and contained hub genes related to adipogenesis, cell cycle, inflammation, and protein synthesis. Moreover, after additional functional annotation and network module comparisons, common sub-modules of similar functionality for chicken fat deposition were identified for different chicken lines, apart from modules specific to each chicken line. We further validated the lysosome pathway, and found TFEB and its downstream target genes showed similar expression patterns along with chicken preadipocyte differentiation. Our findings could provide novel insights into the genetic basis of complex adiposity traits, as well as human obesity and related metabolic diseases.

Efficient knock-in at the chicken ovalbumin locus using adenovirus as a CRISPR/Cas9 delivery system

In this study, efficient knock-in (KI) of human epidermal growth factor (hEGF) cDNA at the ovalbumin (OV) locus in cultured chicken cells was achieved using adenovirus as a delivery for CRISPR/Cas9 elements and optimizing donor vector construction. The strategy of recruiting donor DNA to the insertion site further improved the KI efficiency. The inserted hEGF cDNA can expressed in primary oviduct cells and secreted hEGF promoted proliferation of Hela cells. Moreover, we achieved efficient KI in blastoderm cells without altering their induction in vitro and obtained germline chimeric KI chicken embryos by transplanting KI blastoderm cells as well as injecting adenovirus directly, in vivo. Our results provided an efficient KI method for chicken cells and embryos, and lay the foundation for more convenient production of KI chicken at the OV locus, which will promote the development of oviduct-specific bioreactor.