Large-scale production of functional human lysozyme from marker-free transgenic cloned cows

Crystal Structure of Human Lysozyme Complexed with N-Acetyl-α-d-glucosamine

Human lysozyme is a natural non-specific immune protein that participates in the immune response of infants against bacterial and viral infections. Lysozyme is a well-known hydrolase that cleaves peptidoglycan in bacterial cell walls. Several crystal structures of human lysozyme have been reported, but little is known regarding how it recognizes sugar molecules. In this study, the crystal structures of human lysozyme in its native and two N-acetyl-α-d-glucosamine (α-D-NAG)-bound forms were determined at 1.3 Å and 1.55/1.60 Å resolution, respectively. Human lysozyme formed a typical c-type lysozyme fold and the α-D-NAG molecule was bound to the middle of subsites C and D. The N-acetyl and glucosamine groups of α-D-NAG were stabilized by hydrophobic interactions (Val117, Ala126, and Trp127), hydrogen bonds (Asn64, Asn78, Ala126, and Val128), and water bridges. Conformational changes of Arg80, Tyr81, Val128, and Arg131 of human lysozyme were observed due to the interactions of α-D-NAG with the active-site cleft. The binding configuration of α-D-NAG in human lysozyme was distinct compared with that of other sugar-bound lysozymes. Findings from this structural analysis provide a better understanding of the sugar recognition of human lysozyme during the immune response to microbial pathogens.

Cows as Bioreactors for the Production of Nutritionally and Biomedically Significant Proteins

Dairy and beef cattle make a vital contribution to global nutrition, and since their domestication, they have been continuously exposed to natural and artificial selection to improve production characteristics. The technologies of transgenesis and gene editing used in cattle are responsible for generating news characteristics in bovine breeding, such as alteration of nutritional components of milk and meat enhancing human health benefits, disease resistance decreasing production costs and offering safe products for human food, as well as the recombinant protein production of biomedical significance. Different methodologies have been used to generate transgenic cattle as bioreactors. These methods include the microinjection of vectors in pronuclear, oocyte or zygote, sperm-mediate transgenesis, and somatic cell nuclear transfer. Gene editing has been applied to eliminate unwanted genes related to human and animal health, such as allergy, infection, or disease, and to insert transgenes into specific sites in the host genome. Methodologies for the generation of genetically modified cattle are laborious and not very efficient. However, in the last 30 years, transgenic animals were produced using many biotechnological tools. The result of these modifications includes (1) the change of nutritional components, including proteins, amino acids and lipids for human nutrition; (2) the removal allergic proteins milk; (3) the production of cows resistant to disease; or (4) the production of essential proteins used in biomedicine (biomedical proteins) in milk and blood plasma. The genetic modification of cattle is a powerful tool for biotechnology. It allows for the generation of new or modified products and functionality that are not currently available in this species.

Generation of Monogenetic Cattle by Different Techniques of Embryonic Cell and Somatic Cell Cloning – Their Application to Biotechnological, Agricultural, Nutritional, Biomedical and Transgenic Research – A Review

The development of effective approaches for not only the in vitro maturation (IVM) of heifer/cow oocytes and their extracorporeal fertilization (IVF) but also the non-surgical collection and transfer of bovine embryos has given rise to optimizing comprehensive in vitro embryo production (IVP) technology and improving other assisted reproductive technologies (ART s), such as cattle cloning by embryo bisection, embryonic cell nuclear transfer (ECNT) and somatic cell nuclear transfer (SCNT). The primary goal of the present paper is to demonstrate the progress and achievements in the strategies utilized for embryonic cell cloning and somatic cell cloning in cattle. Moreover, the current article is focused on recognizing and identifying the suitability and reliability of bovine cloning techniques for nutritional biotechnology, agri-food and biopharmaceutical industry, biomedical and transgenic research and for the genetic rescue of endangered or extinct breeds and species of domesticated or wild-living artiodactyl mammals (even-toed ungulates) originating from the family Bovidae.

Extranuclear Inheritance of Mitochondrial Genome and Epigenetic Reprogrammability of Chromosomal Telomeres in Somatic Cell Cloning of Mammals

The effectiveness of somatic cell nuclear transfer (SCNT) in mammals seems to be still characterized by the disappointingly low rates of cloned embryos, fetuses, and progeny generated. These rates are measured in relation to the numbers of nuclear-transferred oocytes and can vary depending on the technique applied to the reconstruction of enucleated oocytes. The SCNT efficiency is also largely affected by the capability of donor nuclei to be epigenetically reprogrammed in a cytoplasm of reconstructed oocytes. The epigenetic reprogrammability of donor nuclei in SCNT-derived embryos appears to be biased, to a great extent, by the extranuclear (cytoplasmic) inheritance of mitochondrial DNA (mtDNA) fractions originating from donor cells. A high frequency of mtDNA heteroplasmy occurrence can lead to disturbances in the intergenomic crosstalk between mitochondrial and nuclear compartments during the early embryogenesis of SCNT-derived embryos. These disturbances can give rise to incorrect and incomplete epigenetic reprogramming of donor nuclei in mammalian cloned embryos. The dwindling reprogrammability of donor nuclei in the blastomeres of SCNT-derived embryos can also be impacted by impaired epigenetic rearrangements within terminal ends of donor cell-descended chromosomes (i.e., telomeres). Therefore, dysfunctions in epigenetic reprogramming of donor nuclei can contribute to the enhanced attrition of telomeres. This accelerates the processes of epigenomic aging and replicative senescence in the cells forming various tissues and organs of cloned fetuses and progeny. For all the above-mentioned reasons, the current paper aims to overview the state of the art in not only molecular mechanisms underlying intergenomic communication between nuclear and mtDNA molecules in cloned embryos but also intrinsic determinants affecting unfaithful epigenetic reprogrammability of telomeres. The latter is related to their abrasion within somatic cell-inherited chromosomes.

Association between Bioactive Molecules in Breast Milk and Type 1 Diabetes Mellitus

The association between breastfeeding and type 1 diabetes mellitus (T1DM) is controversial. However, several recent studies have established a link between these two factors, necessitating a need to review this subject to raise public awareness. Current research indicates that breast milk contains a variety of bioactive substances including immunoglobulins, oligosaccharides, insulin, lactoferrin, lysozyme, cytokines, epidermal growth factors, leukocytes, nucleotides, beneficial bacteria and vitamins. Such substances strengthen the breastfeeding infant's immune system, both directly, by increasing gut microbiota diversity and attacking harmful bacteria and pro-inflammatory molecules, and indirectly, by increasing thymus performance. Accordingly, a lack of or inadequate breastfeeding may predispose infants to several autoimmune disorders, including T1DM. Nursing mothers and caregivers are therefore advised to follow optimal breastfeeding practices prior to introducing complementary foods.

Nanomedical Relevance of the Intermolecular Interaction Dynamics-Examples from Lysozymes and Insulins

Insulin and lysozyme share the common features of being prone to aggregate and having biomedical importance. Encapsulating lysozyme and insulin in micellar nanoparticles probably would prevent aggregation and facilitate oral drug delivery. Despite the vivid structural knowledge of lysozyme and insulin, the environment-dependent oligomerization (dimer, trimer, and multimer) and associated structural dynamics remain elusive. The knowledge of the intra- and intermolecular interaction profiles has cardinal importance for the design of encapsulation protocols. We have employed various biophysical methods such as NMR spectroscopy, X-ray crystallography, Thioflavin T fluorescence, and atomic force microscopy in conjugation with molecular modeling to improve the understanding of interaction dynamics during homo-oligomerization of lysozyme (human and hen egg) and insulin (porcine, human, and glargine). The results obtained depict the atomistic intra- and intermolecular interaction details of the homo-oligomerization and confirm the propensity to form fibrils. Taken together, the data accumulated and knowledge gained will further facilitate nanoparticle design and production with insulin or lysozyme-related protein encapsulation.

Production of hypoallergenic milk from DNA-free beta-lactoglobulin (BLG) gene knockout cow using zinc-finger nucleases mRNA

The whey protein β-lactoglobulin (BLG) is a major milk allergen which is absent in human milk. Here, we for the first time generated DNA-free BLG bi-allelic knockout cow by zinc-finger nuclease (ZFNs) mRNA and produced BLG-free milk. According to the allergenicity evaluation of BLG-free milk, we found it can trigger lower allergic reaction of Balb/c mice including the rectal temperature drop and the allergen-specific immunoglobulin IgE production; BLG free-milk was easily digested by pepsin at 2 min, while BLG in control milk was still not completely digested after 60 min, and the binding of IgE from cow's milk allergy (CMA) patients to BLG free-milk was significantly lower than that to the control milk. Meanwhile, the genome sequencing revealed that our animal is free of off-target events. Importantly, editing animal genomes without introducing foreign DNA into cells may alleviate regulatory concerns related to foods produced by genome edited animals. Finally, the ZFNs-mediated targeting in cow could be transmitted through the germline by breeding. These findings will open up unlimited possibilities of modifying milk composition to make it more suitable for human health and also improve the functional properties of milk.

Efficient targeted integration into the bovine Rosa26 locus using TALENs

The genetic modification of cattle has many agricultural and biomedical applications. However, random integration often results in the unstable expression of transgenes and unpredictable phenotypes. Targeting genes to the "safe locus" and stably expressing foreign genes at a high level are desirable methods for overcoming these hurdles. The Rosa26 locus has been widely used to produce genetically modified animals in some species expressing transgenes at high and consistent levels. For the first time, we identified a bovine orthologue of the mouse Rosa26 locus through a genomic sequence homology analysis. According to 5' rapid-amplification of cDNA ends (5'RACE), 3' rapid-amplification of cDNA ends (3'RACE), reverse transcription PCR (RT-PCR) and quantitative PCR (Q-PCR) experiments, this locus encodes a long noncoding RNA (lncRNA) comprising two exons that is expressed ubiquitously and stably in different tissues. The bovine Rosa26 (bRosa26) locus appears to be highly amenable to transcription activator-like effector nucleases (TALENs)-mediated knock-in, and ubiquitous expression of enhanced green fluorescent protein (EGFP) inserted in the bRosa26 locus was observed in various stages, including cells, embryos, fetus and cattle. Finally, we created a valuable master bRosa26-EGFP fetal fibroblast cell line in which any gene of interest can be efficiently introduced and stably expressed using recombinase-mediated cassette exchange (RMCE). The new tools described here will be useful for a variety of studies using cattle.

Bifunctionality of Iminodiacetic Acid-Modified Lysozyme on Inhibiting Zn2+-Mediated Amyloid β-Protein Aggregation

Aggregation of amyloid β-proteins (Aβ) mediated by metal ions such as Zn²⁺ has been suggested to be implicated in the progression of Alzheimer's disease (AD). Hence, development of bifunctional agents capable of inhibiting Aβ aggregation and modulating metal-Aβ species is an effective strategy for the treatment of AD. In this work, we modified iminodiacetic acid (IDA) onto human lysozyme (hLys) surface to create an inhibitor of Zn²⁺-mediated Aβ aggregation and cytotoxicity. The IDA-modified hLys (IDA-hLys) retained the stability and biocompatibility of native hLys. Extensive biophysical and biological analyses indicated that IDA-hLys significantly attenuated Zn²⁺-mediated Aβ aggregation and cytotoxicity due to its strong binding affinity for Zn²⁺, whereas native hLys showed little effect. Stopped-flow fluorescence spectroscopy showed that IDA-hLys could protect Aβ from Zn²⁺-induced aggregation and rapidly depolymerize Zn²⁺-Aβ aggregates. The research indicates that IDA-hLys is a bifunctional agent capable of inhibiting Aβ fibrillization and modulating Zn²⁺-mediated Aβ aggregation and cytotoxicity as a strong Zn²⁺ chelator.

Expression of recombinant human lysozyme in bacterial artificial chromosome transgenic mice promotes the growth of Bifidobacterium and inhibits the growth of Salmonella in the intestine

Targeted gene modification is a novel intervention strategy to increase disease resistance more quickly than traditional animal breeding. Human lysozyme, a natural, non-specific immune factor, participates in innate immunity, exerts a wide range of antimicrobial activities against pathogens, and has immuneregulatory effects. Therefore, it is a candidate gene for improved disease resistance in animals. In this study, we successfully generated a transgenic mouse model by microinjecting a modified bacterial artificial chromosome containing a recombinant human lysozyme (rhLZ) gene into the pronuclei of fertilized mouse embryos. rhLZ was expressed in serum, liver, spleen, lung, kidney, stomach, small intestine, and large intestine but not in milk. rhLZ protein concentrations in the serum of transgenic mice ranged from 2.09 to 2.60 mg/l. To examine the effect of rhLZ on intestinal microbiota, total aerobes, total anaerobes, Clostridium, Enterococcus, Streptococcus, Salmonella, Escherichia coli, Staphylococcus, Bifidobacterium, and Lactobacillus were measured in the intestines of transgenic and wild type mice. Results showed that Bifidobacteria were significantly increased (p < 0.001), whereas Salmonella were significantly decreased (p < 0.001) in transgenic mice compared to wild type mice. Our study suggests that rhLZ expression is a potential strategy to increase animal disease resistance.

Lysozyme improves gut performance and protects against enterotoxigenic Escherichia coli infection in neonatal piglets

Diarrhea remains one of the leading causes of morbidity and mortality globally, with enterotoxigenic Escherichia coli (ETEC) constituting a major causative pathogen. The development of alternative treatments for diarrhea that do not involve chemotherapeutic drugs or result in antibiotic resistance is critical. Considering that lysozyme is a naturally occurring antimicrobial peptide, in a previous study we developed a transgenic pig line that expresses recombinant human lysozyme (hLZ) in its milk. In the present study, we examined the protective effects of the consumption of this milk against ETEC infection in neonatal piglets. We found that consuming hLZ milk facilitated faster recovery from infection and decreased mortality and morbidity following an ETEC oral inoculation or infection acquired by contact-exposure. The protective effect of hLZ was associated with the enrichment of intestinal bacteria that improve gut health, such as Lactobacillus, and the enhancement of the mucosal IgA response to the ETEC-induced diarrhea. Our study revealed potential protective mechanisms underlying the antimicrobial activity of human lysozyme, validating the use of lysozyme as an effective preventive measure for diarrhea.

Purification and characterization of recombinant human bile salt-stimulated lipase expressed in milk of transgenic cloned cows

Bile salt-stimulated lipase (BSSL) is a lipolytic digestive enzyme with broad substrate specificity secreted from exocrine pancreas into the intestinal lumen in all species and from the lactating mammary gland into the milk of some species, notably humans but not cows. BSSL in breast milk facilitates digestion and absorption of milk fat and promotes growth of small for gestational age preterm infants. Thus, purified recombinant human BSSL (rhBSSL) can be used for treatment of patients with fat malabsorption and expressing rhBSSL in the milk of transgenic cloned cows would therefore be a mean to meet a medical need. In the present study, a vector pBAC-hLF-hBSSL was constructed, which efficiently expressed active rhBSSL in milk of transgenic cloned cows to a concentration of 9.8 mg/ml. The rhBSSL purified from cow milk had the same enzymatic activity, N-terminal amino acid sequence, amino acid composition and isoelectric point and similar physicochemical characteristics as human native BSSL. Our study supports the use of transgenic cattle for the cost-competitive, large-scale production of therapeutic rhBSSL.