The transgenic animal platform for biopharmaceutical production

Genome editing: An insight into disease resistance, production efficiency, and biomedical applications in livestock

One of the primary concerns for the survival of the human species is the growing demand for food brought on by an increasing global population. New developments in genome-editing technology present promising opportunities for the growth of wholesome and prolific farm animals. Genome editing in large animals is used for a variety of purposes, including biotechnology to improve food production, animal health, and pest management, as well as the development of animal models for fundamental research and biomedicine. Genome editing entails modifying genetic material by removing, adding, or manipulating particular DNA sequences from a particular locus in a way that does not happen naturally. The three primary genome editors are CRISPR/Cas 9, TALENs, and ZFNs. Each of these enzymes is capable of precisely severing nuclear DNA at a predetermined location. One of the most effective inventions is base editing, which enables single base conversions without the requirement for a DNA double-strand break (DSB). As reliable methods for precise genome editing in studies involving animals, cytosine and adenine base editing are now well-established. Effective zygote editing with both cytosine and adenine base editors (ABE) has resulted in the production of animal models. Both base editors produced comparable outcomes for the precise editing of point mutations in somatic cells, advancing the field of gene therapy. This review focused on the principles, methods, recent developments, outstanding applications, the advantages and disadvantages of ZFNs, TALENs, and CRISPR/Cas9 base editors, and prime editing in diverse lab and farm animals. Additionally, we address the methodologies that can be used for gene regulation, base editing, and epigenetic alterations, as well as the significance of genome editing in animal models to better reflect real disease. We also look at methods designed to increase the effectiveness and precision of gene editing tools. Genome editing in large animals is used for a variety of purposes, including biotechnology to improve food production, animal health, and pest management, as well as the development of animal models for fundamental research and biomedicine. This review is an overview of the existing knowledge of the principles, methods, recent developments, outstanding applications, the advantages and disadvantages of zinc finger nucleases (ZFNs), transcription-activator-like endonucleases (TALENs), and clustered regularly interspaced short palindromic repeats associated protein 9 (CRISPR/Cas 9), base editors and prime editing in diverse lab and farm animals, which will offer better and healthier products for the entire human race.

Therapeutic proteins: developments, progress, challenges, and future perspectives

Proteins are considered magic molecules due to their enormous applications in the health sector. Over the past few decades, therapeutic proteins have emerged as a promising treatment option for various diseases, particularly cancer, cardiovascular disease, diabetes, and others. The formulation of protein-based therapies is a major area of research, however, a few factors still hinder the large-scale production of these therapeutic products, such as stability, heterogenicity, immunogenicity, high cost of production, etc. This review provides comprehensive information on various sources and production of therapeutic proteins. The review also summarizes the challenges currently faced by scientists while developing protein-based therapeutics, along with possible solutions. It can be concluded that these proteins can be used in combination with small molecular drugs to give synergistic benefits in the future.

Biomanufacturing of glycosylated antibodies: Challenges, solutions, and future prospects

Traditionally, recombinant protein production has been done in several expression hosts of bacteria, fungi, and majorly CHO (Chinese Hamster Ovary) cells; few have high production costs and are susceptible to harmful toxin contamination. Green algae have the potential to produce recombinant proteins in a more sustainable manner. Microalgal diversity leads to offer excellent opportunities to produce glycosylated antibodies. An antibody with humanized glycans plays a crucial role in cellular communication that works to regulate cells and molecules, to control disease, and to stimulate immunity. Therefore, it becomes necessary to understand the role of abiotic factors (light, temperature, pH, etc.) in the production of bioactive molecules and molecular mechanisms of product synthesis from microalgae which would lead to harnessing the potential of algal bio-refinery. However, the potential of microalgae as the source of bio-refinery has been less explored. In the present review, omics approaches for microalgal engineering, methods of humanized glycoproteins production focusing majorly on N-glycosylation pathways, light-based regulation of glycosylation machinery, and production of antibodies with humanized glycans in microalgae with a major emphasis on modulation of post-translation machinery of microalgae which might play a role in better understanding of microalgal potential as a source for antibody production along with future perspectives.

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.

Low levels of endogenous cholinesterases support the choice of cows, sheep and goats for the transgenic expression of human butyrylcholinesterase in milk

Butyrylcholinesterase purified from human plasma (Hu BChE) as well as recombinant (r) Hu BChE are candidate enzymes that can protect humans from toxicity of organophosphorus compounds (OPs). Domestic animals such as cows, pigs, sheep, and goats have been used for the transgenic expression of a variety of valuable therapeutic proteins. Indeed, rHu BChE was successfully expressed in the milk of transgenic goats, but the presence of any endogenous cholinesterases (ChE) in milk would interfere with the isolation of expressed rHu BChE. The aim of this study was to determine the presence of endogenous ChEs in bovine, ovine, caprine, and porcine milk to determine the suitability of these species for the production of rHu BChE. Using acetyl- and butyryl- thiocholine as substrates, ChE activity (2-4 U/mL) was detected in pig milk only. ChE activities in milk from other animals were <0.01 U/mL and could only be detected following enrichment on procainamide-Sepharose gel. Two different methods based on measuring activity in the presence of acetylcholinesterase (AChE)- or BChE- specific inhibitors were used to estimate the proportions of AChE and BChE activities in enriched milk. Monoclonal antibodies (MAbs), against fetal bovine serum AChE that recognize AChEs from ruminants only, were also used to confirm the identity of AChEs. While bovine and ovine milk contain both AChE and BChE activities, caprine and porcine milk contain predominantly BChE activity. The presence of very low ChE activity supports the choice of cows, sheep, and goats for the transgenic expression of rHu BChE in milk.

Animal Transgenesis and Cloning: Combined Development and Future Perspectives

The revolution in animal transgenesis began in 1981 and continues to become more efficient, cheaper, and faster to perform. New genome editing technologies, especially CRISPR-Cas9, are leading to a new era of genetically modified or edited organisms. Some researchers advocate this new era as the time of synthetic biology or re-engineering. Nonetheless, we are witnessing advances in high-throughput sequencing, artificial DNA synthesis, and design of artificial genomes at a fast pace. These advances in symbiosis with animal cloning by somatic cell nuclear transfer (SCNT) allow the development of improved livestock, animal models of human disease, and heterologous production of bioproducts for medical applications. In the context of genetic engineering, SCNT remains a useful technology to generate animals from genetically modified cells. This chapter addresses these fast-developing technologies driving this biotechnological revolution and their association with animal cloning technology.

Genetically Engineered Pigs as Efficient Salivary Gland Bioreactors for Production of Therapeutically Valuable Human Nerve Growth Factor

Farm animal salivary glands hold great potential as efficient bioreactors for production of human therapeutic proteins. Nerve growth factor (NGF) is naturally expressed in animal salivary glands and has been approved for human clinical treatment. This study aims to employ transgenic (TG) pig salivary gland as bioreactors for efficient synthesis of human NGF (hNGF). hNGF-TG pigs were generated by cloning in combination with piggyBac transposon-mediated gene transfer. These hNGF-TG pigs specifically expressed hNGF protein in their salivary glands and secreted it at high levels into saliva. Surgical and nonsurgical approaches were developed to efficiently collect saliva from hNGF-TG pigs. hNGF protein was successfully purified from collected saliva and was verified to be biologically active. In an additional step, the double-transgenic pigs, where the endogenous porcine NGF (pNGF) gene was replaced by another copy of hNGF transgene, were created by cloning combined with CRISPR/Cas9-mediated homologous recombination. These double-transgenic pigs expressed hNGF but not pNGF, thus avoiding possible "contamination" of hNGF with pNGF protein during purification. In conclusion, TG pig salivary glands can be used as robust bioreactors for a large-scale synthesis of functional hNGF or other valuable proteins. This new animal pharming method will benefit both human health and biomedicine.

Application of Gene Editing Technology in Resistance Breeding of Livestock

As a new genetic engineering technology, gene editing can precisely modify the specific gene sequence of the organism’s genome. In the last 10 years, with the rapid development of gene editing technology, zinc-finger nucleases (ZFNs), transcription activator-like endonucleases (TALENs), and CRISPR/Cas9 systems have been applied to modify endogenous genes in organisms accurately. Now, gene editing technology has been used in mice, zebrafish, pigs, cattle, goats, sheep, rabbits, monkeys, and other species. Breeding for disease-resistance in agricultural animals tends to be a difficult task for traditional breeding, but gene editing technology has made this easier. In this work, we overview the development and application of gene editing technology in the resistance breeding of livestock. Also, we further discuss the prospects and outlooks of gene editing technology in disease-resistance breeding.

Design and production strategies for developing a recombinant butyrylcholinesterase medical countermeasure for Organophosphorus poisoning

Organophosphorus nerve agents represent a serious chemical threat due to their ease of production and scale of impact. The recent use of the nerve agent Novichok has re-emphasised the need for broad-spectrum medical countermeasures (MCMs) to these agents. However, current MCMs are limited. Plasma derived human butyrylcholinesterase (huBChE) is a promising novel bioscavenger MCM strategy, but is prohibitively expensive to isolate from human plasma at scale. Efforts to produce recombinant huBChE (rBChE) in various protein expression platforms have failed to achieve key critical attributes of huBChE such as circulatory half-life. These proteins often lack critical features such as tetrameric structure and requisite post-translational modifications. This review evaluates previous attempts to generate rBChE and assesses recent advances in mammalian cell expression and protein engineering strategies that could be deployed to achieve the required half-life and yield for a viable rBChE MCM. This includes the addition of a proline-rich attachment domain, fusion proteins, post translational modifications, expression system selection and optimised downstream processes. Whilst challenges remain, a combinatorial approach of these strategies demonstrates potential as a technically feasible approach to achieving a bioactive and cost effective bioscavenger MCM.

Expression of a triple mutational des-pGlu brazzein in transgenic mouse milk

Brazzein has excellent potential for use as a sweetener because of its high level of sweetening potency and stability against extreme temperature and pH. It is extracted from the tropical and difficult—to‐cultivate African plant Pentadiplandra brazzeana, which hampers its commercial viability. Here we report the mammary‐specific expression of wildtype or triple mutational (H31R/E36D/E41A) des‐pGlu brazzeins in the milk of transgenic mice. Using enzyme‐linked immunoassay (ELISA), western blot, and sweetness intensity testing, we confirmed that the triple mutation made the des‐pGlu brazzein molecule 10,000 times sweeter than sucrose in a weight base, even after 10 min of incubation at 100 °C; in addition, the triple mutant was also significantly sweeter than the wildtype des‐pGlu brazzein. This study provides new insights for producing brazzein or brazzein‐sweetened milk from animals for use in food and healthcare applications.

Developmental analysis of reconstructed embryos of second-generation cloned transgenic goats

To improve the efficiency of the production of transgenic cloned goats by somatic cell nuclear transfer (SCNT), the development of reconstructed embryos of first-generation (G1) and second-generation (G2) cloned transgenic goats were compared and analyzed. Primary transgenic fetal fibroblasts were used as donor cells for G1 somatic cell nuclear transfer (SCNT). When the G1 transgenic embryos developed to 35 days in the recipient goats, transgenic fetal fibroblasts were isolated from them and used as donor cells for the G2 clone. In the G1 clones, the average fusion rate of reconstructed embryos was 73.62±2.9%, the average development rate (2-4 cells) was 33.96±2.36%, and the pregnancy rate of transplant recipients was 31.91%. In the G2 clones, the average fusion rate of the reconstructed embryos was 90.29±2.03%, the average development rate was 66.46±3.30%, and the pregnancy rate was 58.14%. These results indicate that in the G2 clones, the fusion rate of eggs, the development rate of reconstructed embryos, and the pregnancy rate of transplant recipients were significantly higher than those of G1 clones. We believe these results will lay a solid foundation for the efficient production of transgenic cloned animals in the future.

The Improved Milk Quality and Enhanced Anti-Inflammatory Effect in Acetylserotonin-O-methyltransferase (ASMT) Overexpressed Goats: An Association with the Elevated Endogenous Melatonin Production

Background: Transgenic animal production is an important means of livestock breeding and can be used to model pharmaceutical applications. Methods: In this study, to explore the biological activity of endogenously produced melatonin, Acetylserotonin-O-methyltransferase (ASMT)-overexpressed melatonin-enriched dairy goats were successfully generated through the use of pBC1-ASMT expression vector construction and prokaryotic embryo microinjection. Results: These transgenic goats have the same normal phenotype as the wild-type goats (WT). However, the melatonin levels in their blood and milk were significantly increased (p < 0.05). In addition, the quality of their milk was also improved, showing elevated protein content and a reduced somatic cell number compared to the WT goats. No significant changes were detected in the intestinal microbiota patterns between groups. When the animals were challenged by the intravenous injection of E. coli, the ASMT-overexpressed goats had a lower level of pro-inflammatory cytokines and higher anti-inflammatory cytokines compared to the WT goats. Metabolic analysis uncovered a unique arachidonic acid metabolism pattern in transgenic goats. Conclusions: The increased melatonin production due to ASMT overexpression in the transgenic goats may have contributed to their improved milk quality and enhanced the anti-inflammatory ability compared to the WT goats.

Use of Genome Editing Techniques to Produce Transgenic Farm Animals

Recombinant proteins are essential for the treatment and diagnosis of clinical human ailments. The availability and biological activity of recombinant proteins is heavily influenced by production platforms. Conventional production platforms such as yeast, bacteria, and mammalian cells have biological and economical challenges. Transgenic livestock species have been explored as an alternative production platform for recombinant proteins, predominantly through milk secretion; the strategy has been demonstrated to produce large quantities of biologically active proteins. The major limitation of utilizing livestock species as bioreactors has been efforts required to alter the genome of livestock. Advancements in the genome editing field have drastically improved the ability to genetically engineer livestock species. Specifically, genome editing tools such as the CRISPR/Cas9 system have lowered efforts required to generate genetically engineered livestock, thus minimizing restrictions on the type of genetic modification in livestock. In this review, we discuss characteristics of transgenic animal bioreactors and how the use of genome editing systems enhances design and availability of the animal models.

Recombinant Protein Production and Purification of Insoluble Proteins

Proteins are synthesized in heterologous systems because of the impossibility to obtain satisfactory yields from natural sources. The efficient production of soluble and functional recombinant proteins is among the main goals in the biotechnological field. In this context, it is important to point out that under stress conditions, protein folding machinery is saturated and this promotes protein misfolding and, consequently, protein aggregation. Thus, the selection of the optimal expression organism and its growth conditions to minimize the formation of insoluble protein aggregates should be done according to the protein characteristics and downstream requirements. Escherichia coli is the most popular recombinant protein expression system despite the great development achieved so far by eukaryotic expression systems. Besides, other prokaryotic expression systems, such as lactic acid bacteria and psychrophilic bacteria, are gaining interest in this field. However, it is worth mentioning that prokaryotic expression system poses, in many cases, severe restrictions for a successful heterologous protein production. Thus, eukaryotic systems such as mammalian cells, insect cells, yeast, filamentous fungus, and microalgae are an interesting alternative for the production of these difficult-to-express proteins.

Physiological impact of the environment on the welfare of transgenic goats raised in a tropical climate

The present study evaluated the general welfare state of two strains of transgenic goats bred in a region with a hot and humid tropical climate. Nine females were used, being three transgenic for human lysozyme (hLZ group), three transgenic for human glucocerebrosidase (hGCase group), and three non-transgenic (control group). The temperature and humidity index (THI) were recorded during the morning, afternoon, and evening. The physiological parameters measured were respiratory rate, heart rate, and rectal and vaginal temperatures. Venous blood samples were collected using Vacutainer® tubes containing 10% ethylenediaminetetraacetic acid (EDTA). Also, analysis of erythrogram, leukogram, and some biochemical parameters of serum was performed. It was observed that the afternoon shift presented the largest THI, being potentially more impactful on the physiology of animals. In general, respiratory and heart rates were higher in transgenic animals, especially in the hLZ group compared to the control group (P < 0.05). Regarding the hematological parameters, the quantification of red blood cells, hemoglobin, and hematocrit was significantly lower (P < 0.05) in the hGCase group compared to that in the hLZ and control. The leukocyte count was considerably lower (P < 0.05) in the hLZ group compared to that in the hGCase and control. Correlation analysis showed that the increase in THI was associated with a change in physiological parameters normally used as indicators of thermal stress. Despite the differences found among the experimental groups, all the physiological parameters remained within the normal limits recommended for the goat species. Further studies involving a larger number of animals from different categories should be carried out to elucidate the impacts that transgenesis can have on animal welfare under different THI conditions.

Current views on N-glycolylneuraminic acid in therapeutic recombinant proteins

The incorporation of the non-human N-glycolylneuraminic acid (Neu5Gc) in therapeutic recombinant proteins raises clinical concerns due to its immunogenic potential and the high prevalence of pre-existing anti-Neu5Gc antibodies in humans. The scientific literature is ambiguous regarding the actual impact of Neu5Gc-containing biotherapeutics as no severe adverse clinical manifestations were unequivocally attributed to Neu5Gc for currently marketed biotherapeutics. This review discusses structural and functional considerations of Neu5Gc-containing glycans regarding the potential impact on drug clearance, their recognition by pre-existing antibodies, and recent hypotheses regarding the tolerance to low Neu5Gc levels. Furthermore, it provides recommendations regarding the standardization of analysis and reporting, analytical aspects relevant for assessing risks associated with Neu5Gc-containing biotherapeutics, and approaches to minimize Neu5Gc incorporation in recombinant protein manufacturing.

Restoring mammary gland structures and functions with autogenous cell therapy

In somatic cell reprogramming, cells must escape the somatic cell-specific gene expression program to adopt other cell fates. Here, in vitro chemical induction with RepSox generated chemically induced mammary epithelial cells (CiMECs) with milk secreting functions from goat ear fibroblasts (GEFs). Transplanted CiMECs regenerated the normal mammary gland structure with milk-secreting functions in nude mice. Single-cell RNA sequencing revealed that during the reprogramming process, GEFs may sequentially undergo embryonic ectoderm (EE)-like and different MEC developmental states and finally achieve milk secreting functions, bypassing the pluripotent state. Mechanistically, Smad3 upregulation induced by transforming growth factor β (TGFβ) receptor 1 (TGFβR1) downregulation led to GEF reprogramming into CiMECs without other reprogramming factors. The TGFβR1-Smad3 regulatory effects will provide new insight into the TGFβ signaling pathway regulation of somatic cell reprogramming. These findings suggest an innovative strategy for autogenous cell therapy for mammary gland defects and the production of transgenic mammary gland bioreactors.

Expression and characterization of a novel single-chain anti-vascular endothelial growth factor antibody in the goat milk

Vascular endothelial growth factor (VEGF) has essential functions in angiogenesis, endothelial cell proliferation, migration, and tumor invasion. Different approaches have been developed to suppress tumor angiogenesis, which is considered a hallmark of cancer. Anti-VEGF monoclonal antibodies constitute an important strategy for cancer immunotherapy, which has been produced on several platforms. In this study, a novel single-chain anti-VEGF monoclonal antibody (scVEGFmAb) was produced in the goat mammary gland by adenoviral transduction. scVEGFmAb was purified by affinity chromatography. N-glycans were analyzed by exoglycosidase digestion and hydrophilic interaction ultra-performance liquid chromatography coupled to electrospray ionization mass spectrometry. The biological activity of scVEGFmAb was assessed by scratch and mouse aortic ring assays. scVEGFmAb was produced at 0.61 g/L in the goat milk, and its purification rendered 95 % purity. N-glycans attached to scVEGFmAb backbone were mainly neutral biantennary core fucosylated with Galβ1,4GlcNAc motif, and charged structures were capped with Neu5Ac and Neu5Gc. The chimeric molecule significantly prevented cell migration and suppressed microvessel sprouting. These results demonstrated for the first time the feasibility of producing an anti-VEGF therapeutic antibody in the milk of non-transgenic goats with the potential to counteract tumor angiogenesis.

Recombinant active Peptides and their Therapeutic functions

Recombinant active peptides are utilized as diagnostic and biotherapeutics in various maladies and as bacterial growth inhibitors in the food industry. This consequently stimulated the need for recombinant peptides' production, which resulted in about 19 approved biotech peptides of 1-100 amino acids commercially available. While most peptides have been produced by chemical synthesis, the production of lengthy and complicated peptides comprising natural amino acids has been problematic with low quantity. Recombinant peptide production has become very vital, cost-effective, simple, environmentally friendly with satisfactory yields. Several reviews have focused on discussing expression systems, advantages, disadvantages, and alternatives strategies. Additionally, the information on the antimicrobial activities and other functions of multiple recombinant peptides is challenging to access and is scattered in literature apart from the food and drug administration (FDA) approved ones. From the reports that come to our knowledge, there is no existing review that offers substantial information on recombinant active peptides developed by researchers and their functions. This review provides an overview of some successfully produced recombinant active peptides of ≤100 amino acids by focusing on their antibacterial, antifungal, antiviral, anticancer, antioxidant, antimalarial, and immune-modulatory functions. It also elucidates their modes of expression that could be adopted and applied in future investigations. We expect that the knowledge available in this review would help researchers involved in recombinant active peptide development for therapeutic uses and other applications.

Biological drug therapy for ocular angiogenesis: Anti-VEGF agents and novel strategies based on nanotechnology

Currently, biological drug therapy for ocular angiogenesis treatment is based on the administration of anti‐VEGF agents via intravitreal route. The molecules approved with this purpose for ocular use include pegaptanib, ranibizumab, and aflibercept, whereas bevacizumab is commonly off‐label used in the clinical practice. The schedule dosage involves repeated intravitreal injections of anti‐VEGF agents to achieve and maintain effective concentrations in retina and choroids, which are administrated as solutions form. In this review article, we describe the features of different anti‐VEGF agents, major challenges for their ocular delivery and the nanoparticles in development as delivery system of them. In this way, several polymeric and lipid nanoparticles are explored to load anti‐VEGF agents with the aim of achieving sustained drug release and thus, minimize the number of intravitreal injections required. The main challenges were focused in the loading the molecules that maintain their bioactivity after their release from nanoparticulate system, followed the evaluation of them through studies of formulation stability, pharmacokinetic, and efficacy in in vitro and in vivo models. The analysis was based on the information published in peer‐reviewed published papers relevant to anti‐VEGF treatments and nanoparticles developed as ocular anti‐VEGF delivery system.

Development of a Mucus Gland Bioreactor in Loach Paramisgurnus dabryanus

Most currently available bioreactors have some defects in the expression, activity, or purification of target protein and peptide molecules, whereas the mucus gland of fish can overcome these defects to become a novel bioreactor for the biopharmaceutical industry. In this study, we have evaluated the practicability of developing a mucus gland bioreactor in loach (Paramisgurnus dabryanus). A transgenic construct pT2-krt8-IFN1 was obtained by subcloning the promoter of zebrafish keratin 8 gene and the type I interferon (IFN1) cDNA of grass carp into the SB transposon. The IFN1 expressed in CIK cells exhibited an antiviral activity against the replication of GCRV873 and activated two genes downstream of JAK-STAT signaling pathway. A transgenic loach line was then generated by microinjection of the pT2-krt8-IFN1 plasmids and in vitro synthesized capped SB11 mRNA. Southern blots indicated that a single copy of IFN1 gene was stably integrated into the genome of transgenic loach. The expression of grass carp IFN1 in transgenic loaches was detected with RT-PCR and Western blots. About 0.0825 µg of grass carp IFN1 was detected in 20 µL mucus from transgenic loaches. At a viral titer of 1 × 10³ PFU/mL, plaque numbers on plates containing mucus from transgenic loaches reduced by 18% in comparison with those of the control, indicating that mucus of IFN1-transgenic loaches exhibited an antiviral activity. Thus, we have successfully created a mucus gland bioreactor that has great potential for the production of various proteins and peptides.

Production of Recombinant Monoclonal Antibodies in the Egg White of Gene-Targeted Transgenic Chickens

Increased commercial demand for monoclonal antibodies (mAbs) has resulted in the urgent need to establish efficient production systems. We previously developed a transgenic chicken bioreactor system that effectively produced human cytokines in egg whites using genome-edited transgenic chickens. Here, we describe the application of this system to mAb production. The genes encoding the heavy and light chains of humanized anti-HER2 mAb, linked by a 2A peptide sequence, were integrated into the chicken ovalbumin gene locus using a CRISPR/Cas9 protocol. The knock-in hens produced a fully assembled humanized mAb in their eggs. The mAb expression level in the egg white was 1.4–1.9 mg/mL, as determined by ELISA. Furthermore, the antigen binding affinity of the anti-HER2 mAb obtained was estimated to be equal to that of the therapeutic anti-HER2 mAb (trastuzumab). In addition, antigen-specific binding by the egg white mAb was demonstrated by immunofluorescence against HER2-positive and -negative cells. These results indicate that the chicken bioreactor system can efficiently produce mAbs with antigen binding capacity and can serve as an alternative production system for commercial mAbs.

Transgenic Rabbit Models: Now and the Future

Transgenic rabbits have contributed to the progress of biomedical science as human disease models because of their unique features, such as the lipid metabolism system similar to humans and medium body size that facilitates handling and experimental manipulation. In fact, many useful transgenic rabbits have been generated and used in research fields such as lipid metabolism and atherosclerosis, cardiac failure, immunology, and oncogenesis. However, there have been long-term problems, namely that the transgenic efficiency when using pronuclear microinjection is low compared with transgenic mice and production of knockout rabbits is impossible owing to the lack of embryonic stem cells for gene targeting in rabbits. Despite these limitations, the emergence of novel genome editing technology has changed the production of genetically modified animals including the rabbit. We are finally able to produce both transgenic and knockout rabbit models to analyze gain- and loss-of-functions of specific genes. It is expected that the use of genetically modified rabbits will extend to various research fields. In this review, we describe the unique features of rabbits as laboratory animals, the current status of their development and use, and future perspectives of transgenic rabbit models for human diseases.

Simplified pipelines for genetic engineering of mammalian embryos by CRISPR-Cas9 electroporation†

Gene editing technologies, such as CRISPR-Cas9, have important applications in mammalian embryos for generating novel animal models in biomedical research and lines of livestock with enhanced production traits. However, the lack of methods for efficient introduction of gene editing reagents into zygotes of various species and the need for surgical embryo transfer in mice have been technical barriers of widespread use. Here, we described methodologies that overcome these limitations for embryos of mice, cattle, and pigs. Using mutation of the Nanos2 gene as a readout, we refined electroporation parameters with preassembled sgRNA-Cas9 RNPs for zygotes of all three species without the need for zona pellucida dissolution that led to high-efficiency INDEL edits. In addition, we optimized culture conditions to support maturation from zygote to the multicellular stage for all three species that generates embryos ready for transfer to produce gene-edited animals. Moreover, for mice, we devised a nonsurgical embryo transfer method that yields offspring at an efficiency comparable to conventional surgical approaches. Collectively, outcomes of these studies provide simplified pipelines for CRISPR-Cas9-based gene editing that are applicable in a variety of mammalian species.

Evaluating the effect of TLR4-overexpressing on the transcriptome profile in ovine peripheral blood mononuclear cells

Background

Toll-like receptor 4 (TLR4) plays an important role in the elimination of Gram-negative bacteria infections and the initiation of antiinflammatory response. Using the technology of pronuclear microinjection, genetically modified (GM) sheep with TLR4 overexpression were generated. Previous studies have shown that these GM sheep exhibited a higher inflammatory response to Gram-negative bacteria infection than wild type (WT) sheep. In order to evaluate the gene expression of GM sheep and study the co-expressed and downstream genes for TLR4, peripheral blood mononuclear cells (PBMC) from TLR4-overexpressing (Tg) and wild type (WT) sheep were selected to discover the transcriptomic differences using RNA-Seq.

Result

An average of 18,754 and 19,530 known genes were identified in the Tg and WT libraries, respectively. A total of 338 known genes and 85 novel transcripts were found to be differentially expressed in the two libraries (p < 0.01). A differentially expressed genes (DEGs) enrichment analysis showed that the GO terms of inflammatory response, cell recognition, etc. were significantly (FDR < 0.05) enriched. Furthermore, the above DEGs were significantly (FDR < 0.05) enriched in the sole KEGG pathway of the Phagosome. Real-time PCR showed the OLR1, TLR4 and CD14 genes to be differentially expressed in the two groups, which validated the DEGs data.

Conclusions

The RNA-Seq results revealed that the overexpressed TLR4 in our experiment strengthened the ovine innate immune response by increasing the phagocytosis in PBMC.

Rescue of caprine fetal ovaries, vitrification and follicular development after xenotransplantation in two immunodeficient mice models

Domestic and wild goats are very susceptible animals to predation, specially when pregnancy occurs. This study aimed to evaluate the use of goat fetal ovarian tissue for vitrification followed by xenotransplantation and fresh xenotransplantation in two immunosuppressed mice models (C57BL/6 SCID and Balb-C NUDE). Goat fetus ovaries were collected in slaughterhouses, divided into small cortical pieces and were destined for fresh xenotransplantation (FX) and cryopreservation followed by xenotransplantation (CX). Five recipients from each lineage were used for FX and 10 animals from each lineage for CX. The mice were euthanized after 65 postoperative days, and the transplants were collected for microscopic assessment. The blood plasma was collected for estradiol measurement. Independently of mice strain, all recipients presented complete estrus cycle in FX and 80% after CX groups. Follicles were observed at all development stages without morphological changes. The volume density and total vessel surface observed in the transplants were different (p <0.01) between groups. The estradiol levels in the recipients did not differ (p <0.05) among the treatments. Thus, it is possible to activate the preantral follicles in the ovaries of fetuses by optimizing germplasm utilization and conservation of domestic and endangered wild goats that are in predatory situations, undesirable drowning or accidental death, since provided conditions for xenotransplantation are performed.

The domesticated buffalo - An emerging model for experimental and therapeutic use of extraembryonic tissues

Large animals play important roles as model animals for biomedical sciences and translational research. The water buffalo (Bubalus bubalis) is an economically important, multipurpose livestock species. Important assisted reproduction techniques, such as in vitro fertilization, cryo-conservation of sperm and embryos, embryo transfer, somatic cell nuclear transfer, genetic engineering, and genome editing have been successfully applied to buffaloes. Recently, detailed whole genome data and transcriptome maps have been generated. In addition, rapid progress has been made in stem cell biology of the buffalo. Apart from embryonic stem cells, bubaline extra-embryonic stem cells have gained particular interest. The multipotency of non-embryonic stem cells has been revealed, and their utility in basic and applied research is currently investigated. In particular, success achieved in bubaline extra-embryonic stem cells may have important roles in experimental biology and therapeutic regenerative medicine. Progress in other farm animals in assisted reproduction techniques, stem cell biology and genetic engineering, which could be of importance for buffalo, will also be briefly summarized.

DNA barcoding reveals that injected transgenes are predominantly processed by homologous recombination in mouse zygote

Mechanisms that ensure repair of double-strand DNA breaks (DSBs) are instrumental in the integration of foreign DNA into the genome of transgenic organisms. After pronuclear microinjection, exogenous DNA is usually found as a concatemer comprising multiple co-integrated transgene copies. Here, we investigated the contribution of various DSB repair pathways to the concatemer formation. We injected mouse zygotes with a pool of linear DNA molecules carrying unique barcodes at both ends and obtained 10 transgenic embryos with 1–300 transgene copies. Sequencing the barcodes allowed us to assign relative positions to the copies in concatemers and detect recombination events that occurred during integration. Cumulative analysis of approximately 1,000 integrated copies reveals that over 80% of them underwent recombination when their linear ends were processed by synthesis-dependent strand annealing (SDSA) or double-strand break repair (DSBR). We also observed evidence of double Holliday junction (dHJ) formation and crossing over during the concatemer formations. Sequencing indels at the junctions between copies shows that at least 10% of DNA molecules introduced into the zygotes are ligated by non-homologous end joining (NHEJ). Our barcoding approach, verified with Pacific Biosciences Single Molecule Real-Time (SMRT) long-range sequencing, documents high activity of homologous recombination after DNA microinjection.

Targeted knock-in into the OVA locus of chicken cells using CRISPR/Cas9 system with homology-independent targeted integration

It is anticipated that transgenic avian species will be used as living bioreactors for the production of biopharmaceutical proteins. Precise tissue-specific expression of exogenous genes is a major challenge for the development of avian bioreactors. No robust vector is currently available for highly efficient and specific expression. In recent years, genome-editing techniques such as the CRISPR/Cas9 system have emerged as efficient and user-friendly genetic modification tools. Here, to apply the CRISPR/Cas9 system for the development of transgenic chickens, guide RNA sequences (gRNAs) of the CRISPR/Cas9 system for the ovalbumin (OVA) locus were evaluated for the oviduct-specific expression of exogenous genes. An EGFP gene expression cassette was introduced into the OVA locus of chicken DF-1 and embryonic fibroblasts using the CRISPR/Cas9 system mediated by homology-independent targeted integration. For the knock-in cells, EGFP expression was successfully induced by activation of the endogenous OVA promoter using the dCas9-VPR transactivation system. The combination of gRNAs designed around the OVA TATA box was important to induce endogenous OVA gene expression with high efficiency. These methods provide a useful tool for studies on the creation of transgenic chicken bioreactors and the activation of tissue-specific promoters.

Production of biologically active human factor IX-Fc fusion protein in the milk of transgenic mice

OBJECTIVE

To investigate the feasibility of producing human IgG1 Fc fragment fused factor IX (FIX-Fc) in the milk of transgenic animals, for an alternative possible solution to the unmet need of FIX-Fc products for hemophilia B treatment.

RESULTS

Six founder lines of transgenic mice harboring FIX-Fc cassette designed to be expressed specifically in the mammary gland were generated. FIX-Fc protein was secreted into the milk of transgenic mice with preserved biological activity (with the highest value of 6.2 IU/mL), similar to that of the non-fused FIX transgenic milk. RT-PCR and immunofluorescence analysis confirmed that FIX-Fc was specifically expressed in the mammary gland. The blood FIX clotting activities were unchanged, and no apparent health defects were observed in the transgenic mice. Moreover, the stability of FIX protein in milk was increased by the Fc fusion.

CONCLUSIONS

It is feasible to produce biologically functional FIX-Fc in the mammary gland of transgenic mice. Our preliminary results provide a foundation for the potential scale-up production of FIX-Fc in the milk of dairy animals.

Embryo-Based Large Fragment Knock-in in Mammals: Why, How and What's Next

Endonuclease-mediated genome editing technologies, most notably CRISPR/Cas9, have revolutionized animal genetics by allowing for precise genome editing directly through embryo manipulations. As endonuclease-mediated model generation became commonplace, large fragment knock-in remained one of the most challenging types of genetic modification. Due to their unique value in biological and biomedical research, however, a diverse range of technological innovations have been developed to achieve efficient large fragment knock-in in mammalian animal model generation, with a particular focus on mice. Here, we first discuss some examples that illustrate the importance of large fragment knock-in animal models and then detail a subset of the recent technological advancements that have allowed for efficient large fragment knock-in. Finally, we envision the future development of even larger fragment knock-ins performed in even larger animal models, the next step in expanding the potential of large fragment knock-in in animal models.

Seeds as Economical Production Platform for Recombinant Proteins

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The cost-effective production of high-quality and biologically active recombinant molecules especially proteins is extremely desirable. Seed-based recombinant protein production platforms are considered as superior choice owing to lack of human/animal pathogenic organisms, lack of cold chain requirements for transportation and long-term storage, easy scalability and development of edible biopharmaceuticals in plants with objective to be used in purified or partially processed form is desirable. This review article summarizes the exceptional features of seed-based biopharming and highlights the needs of exploiting it for commercial purposes. Plant seeds offer a perfect production platform for high-value molecules of industrial as well as therapeutic nature owing to lower water contents, high protein storage capacity, weak protease activity and long-term storage ability at ambient temperature. Exploiting extraordinarily high protein accumulation potential, vaccine antigens, antibodies and other therapeutic proteins can be stored without effecting their stability and functionality up to years in seeds. Moreover, ability of direct oral consumption and post-harvest stabilizing effect of seeds offer unique feature of oral delivery of pharmaceutical proteins and vaccine antigens for immunization and disease treatment through mucosal as well as oral route.

Reproductive technologies in swine

This chapter highlights the importance of reproductive technologies that are applied to porcine breeds. Nowadays the porcine industry, part of a high technological and specialized sector, offers high-quality protein food. The development of the swine industry is founded in the development of breeding/genetics, nutrition, animal husbandry, and animal health. The implementation of reproductive technologies in swine has conducted to levels of productivity never reached before. In addition, the pig is becoming an important species for biomedicine. The generation of pig models for human disease, xenotransplantation, or production of therapeutic proteins for human medicine has in fact generated a growing field of interest.

Recent Developments in Bioprocessing of Recombinant Proteins: Expression Hosts and Process Development

Infectious diseases, along with cancers, are among the main causes of death among humans worldwide. The production of therapeutic proteins for treating diseases at large scale for millions of individuals is one of the essential needs of mankind. Recent progress in the area of recombinant DNA technologies has paved the way to producing recombinant proteins that can be used as therapeutics, vaccines, and diagnostic reagents. Recombinant proteins for these applications are mainly produced using prokaryotic and eukaryotic expression host systems such as mammalian cells, bacteria, yeast, insect cells, and transgenic plants at laboratory scale as well as in large-scale settings. The development of efficient bioprocessing strategies is crucial for industrial production of recombinant proteins of therapeutic and prophylactic importance. Recently, advances have been made in the various areas of bioprocessing and are being utilized to develop effective processes for producing recombinant proteins. These include the use of high-throughput devices for effective bioprocess optimization and of disposable systems, continuous upstream processing, continuous chromatography, integrated continuous bioprocessing, Quality by Design, and process analytical technologies to achieve quality product with higher yield. This review summarizes recent developments in the bioprocessing of recombinant proteins, including in various expression systems, bioprocess development, and the upstream and downstream processing of recombinant proteins.

Surfing the Blood Coagulation Cascade: Insight into the Vital Factor Xa

Factor Xa (FXa) plays a key role in haemostasis, it is a central part of the blood coagulation cascade which catalyzes the production of thrombin and leads to clot formation and wound closure. Therefore, FXa is an attractive target for the development of new anticoagulant agents. In this review, we will first describe the molecular features of this fundamental protein in order to understand its mechanism of action, an essential background for the design of novel inhibitors by means of synthetic organic chemistry or using peptides obtained from recombinant methodologies. Then, we will review the current state of the synthesis of novel direct FXa inhibitors along with their mechanisms of action. Finally, approved reversal agents that aid in maintaining blood haemostasis by using these commercial drugs will also be discussed.

Evaluation of New Genetic Toolkits and Their Role for Ethanol Production in Cyanobacteria

Since the public awareness for climate change has risen, increasing scientific effort has been made to find and develop alternative resources and production processes to reduce the dependency on petrol-based fuels and chemicals of our society. Among others, the biotechnological fuel production, as for example fermenting sugar-rich crops to ethanol, is one of the main strategies. For this purpose, various classical production systems like Escherichia coli or Saccharomyces cerevisiae are used and have been optimized via genetic modifications. Despite the progress made, this strategy competes for nutritional resources and agricultural land. To overcome this problem, various attempts were made for direct photosynthetic driven ethanol synthesis with different microalgal species including cyanobacteria. However, compared to existing platforms, the development of cyanobacteria as photoautotrophic cell factories has just started, and accordingly, the ethanol yield of established production systems is still unreached. This is mainly attributed to low ethanol tolerance levels of cyanobacteria and there is still potential for optimizing the cyanobacteria towards alternative gene expression systems. Meanwhile, several improvements were made by establishing new toolboxes for synthetic biology offering new possibilities for advanced genetic modifications of cyanobacteria. Here, current achievements and innovations of those new molecular tools are discussed.

Development of dairy herd of transgenic goats as biofactory for large-scale production of biologically active recombinant human lactoferrin

The primary male-goats Lac-1 (human lactoferrin gene construct hLF5) and Lac-2 (human lactoferrin gene construct hLF3) with genome containing human lactoferrin gene were bred and the sperm bank of primary male-goats and their male descendents (F₁-F₇) was created. The herd of goats (200 transgenic females) that produced recombinant human lactoferrin (rhLF) in their milk at levels up to 16 g/L was obtained. The rhLF from milk of transgenic goats, natural human lactoferrin (hLF) from woman milk and natural goat lactoferrin (gLF) from milk of non-transgenic goats were purified using cation-exchange chromatography. It has been shown that rhLF is a glycoprotein and its physicochemical characteristics of rhLF are similar to hLf as revealed by different analytical methods including electron paramagnetic resonance, spectrophotometry, differential scanning calorimetry, mass spectrometry and peptide mapping. The high expression level of rhLF achieved in milk of transgenic goats provides a solid basis for developing an efficient and cost-effective downstream processing. The rhLF exhibited a prominent biological activity suggesting it as a promising biopharmaceutical and food supplements.

Comparative analysis of buffalo (Bubalus bubalis) non-transgenic and transgenic embryos containing human insulin gene, produced by SCNT

Somatic cell nuclear transfer (SCNT), using transgenic donor cells, is a highly efficient method for producing transgenic embryos. We compared the developmental competence, quality and gene expression of transgenic embryos produced by Hand-made cloning from buffalo fetal fibroblasts (BFFs) containing human insulin gene, with non-transgenic embryos produced from BFFs (Controls). The expression vector (pAcISUBC), constructed by inserting human insulin gene between DNA fragments containing mammary gland-specific buffalo β-lactoglobulin (buBLG) promoter and terminator buBLG 3'UTR regions into pAcGFP-N1 vector, was used for obtaining the 11 kb insert for transfection of BFFs by nucleofection. Presence of the transgene in embryos was confirmed by examining GFP expression by RT-PCR and immunofluorescence. The blastocyst rate was lower (P < 0.05) for transgenic embryos than for controls (35.7 ± 1.8% vs 48.7 ± 2.4%). The apoptotic index was higher (P < 0.05) for transgenic than for control blastocysts which, in turn, was higher (P < 0.05) than for IVF counterparts (6.9 ± 0.9, 3.8 ± 0.5 and 1.8 ± 0.3, respectively). The total cell number was similar for transgenic and non-transgenic blastocysts (143.2 ± 17.0 and 137.2 ± 7.6, respectively). The expression level of pro-apoptotic genes BAX and BID but not that of CASP3 and CASP9, and cell cycle check point control-related gene P53 was higher (P < 0.05), and that of development- (IGF-1R and G6PD) and pluripotency-related gene NANOG was lower (P < 0.05) in transgenic than in control embryos. The expression level of epigenetic-related genes DNMT1, DNMT3a and HDAC1 and pluripotency-related gene OCT4 was similar in the two groups. The expression level of BAX, BID, CASP9, P53, DNMT1 and DNMT3a was higher (P < 0.05) and that of OCT4, NANOG IGF-1R and G6PD was lower (P < 0.05) in cloned transgenic than in IVF blastocysts whereas, that of CASP3 and HDAC1 was similar between the two groups. In conclusion, these results suggest that transgenic embryos produced by SCNT have lower developmental competence and quality, and altered gene expression compared to non-transgenic embryos.

Production of transgenic cattle by somatic cell nuclear transfer (SCNT) with the human granulocyte colony-stimulation factor (hG-CSF)

The hG-CSF (human Granulocyte Colony-Stimulating Factor) is a growth and stimulation factor capable of inducing the proliferation of bone marrow cells, several types of leukocytes, among other hematopoietic tissue cells. hG-CSF is used in used to treat anomalies that reder a small number of circulating white blood cells, which may compromise the immune defenses of the affected person. For these reasons, the production of hG-CSF in a bioreactor system using the mammary gland of genetic modified animals is a possibility of adding value to the bovine genetic material and reducing the costs of hG-CSF production in pharmaceutical industry. In this study, we aimed the production of transgenic hG-CSF bovine through the lipofection of bovine primary fibroblasts with an hG-CSF expression cassette and cloning these fibroblasts by the somatic cell nuclear transfer (SCNT) technique. The bovine fibroblasts transfected with the hG-CSF cassette presented a stable insertion of this construct into their genome and were efficiently synchronized to G0/G1 cell cycle stage. The transgenic fibroblasts were cloned by SCNT and produced 103 transferred embryos and 2 pregnancies, one of which reached 7 months of gestation.

The antioxidant components of milk and their role in processing, ripening, and storage: Functional food

The current rate of population growth is so fast that, to feed this massive population, a 2-fold increase in land is required for the production of quality food. Improved dietary products such as milk and its products with antioxidant properties and functional foods of animal origin have been utilized to prevent chronic diseases. The designer milk contains low fat and less lactose, more protein, modified level of fatty acids, and desired amino acid profiles. The importance of milk and its products is due to the presence of protein, bioactive peptides, conjugated linoleic acid, omega-3 fatty acid, Vitamin D, selenium, and calcium. These constituents are present in milk product, play a key role in the physiological activities in human bodies, and act as anti-inflammatory, anti-tumor, antioxidant, hypocholesterolemic, immune boosting, and antimicrobial activities. Consumer awareness regarding benefits of designer foods such as milk and its products is almost non-existent worldwide and needs to be established to reach the benefits of designer food technologies in the near future. The main objective of this review was to collect data on the antioxidant properties of milk and its constituents which keep milk-derived products safe and preserved.

Mucin 2 (MUC2) promoter characterization: an overview

Transgenic livestock have been studied with a well-known interest in improving quantitative and qualitative traits. In order to direct heterologous gene expression, it is indispensable to identify and characterize a promoter suitable for directing the expression of the gene of interest (GOI) in a tissue-specific way. The gastrointestinal tract is a desirable target for gene expression in several mammalian models. Throughout the surface of the intestinal epithelium, there is an intricate polymer network, formed by gel-forming mucins (especially MUC2 and MUC5AC, of which MUC2 is the major one), which plays a protective role due to the formation of a physical, chemical and immunological barrier between the organism and the environment. The characterization of the gel-forming mucins is difficult because of their large size and repetitive DNA sequences and domains. The main mucin in the small and large intestine, mucin 2 (MUC2), is expressed specifically in goblet cells. MUC2 plays an important role in intestinal homeostasis and its disruption is associated with several diseases and carcinomas. This mucin is also an important marker for elucidating mechanisms that regulate differentiation of the secretory cell lineage. This review presents the state of the art of MUC2 promoter structure and functional characterization.

Progress in biopharmaceutical development

Since its introduction in 1982, biopharmaceutical drugs have revolutionized the treatment of a broad spectrum of diseases and are increasingly used in nearly all branches of medicine. In recent years, the biopharmaceuticals market has developed much faster than the market for all drugs and is believed to have great potential for further dynamic growth because of the tremendous demand for these drugs. Biobetters, which contain altered active pharmaceutical ingredients with enhanced efficacy, will play an important role in the development of biopharmaceuticals. Another significant group of biopharmaceuticals are biosimilars. Their introduction in the European Union and, recently, the Unites States markets will reduce the costs of biopharmaceutical treatment. This review highlights recent progress in the field of biopharmaceutical development and issues concerning the registration of innovative biopharmaceuticals and biosimilars. The leading class of biopharmaceuticals, the current biopharmaceuticals market, and forecasts are also discussed.

Development of genome engineering technologies in cattle: from random to specific

The production of transgenic farm animals (e.g., cattle) via genome engineering for the gain or loss of gene functions is an important undertaking. In the initial stages of genome engineering, DNA micro-injection into one-cell stage embryos (zygotes) followed by embryo transfer into a recipient was performed because of the ease of the procedure. However, as this approach resulted in severe mosaicism and has a low efficiency, it is not typically employed in the cattle as priority, unlike in mice. To overcome the above issue with micro-injection in cattle, somatic cell nuclear transfer (SCNT) was introduced and successfully used to produce cloned livestock. The application of SCNT for the production of transgenic livestock represents a significant advancement, but its development speed is relatively slow because of abnormal reprogramming and low gene targeting efficiency. Recent genome editing technologies (e.g., ZFN, TALEN, and CRISPR-Cas9) have been rapidly adapted for applications in cattle and great results have been achieved in several fields such as disease models and bioreactors. In the future, genome engineering technologies will accelerate our understanding of genetic traits in bovine and will be readily adapted for bio-medical applications in cattle.