Egg white proteins

Endocrine and Transcriptome Changes Associated with Testicular Growth and Differentiation in Atlantic Salmon (Salmo salar L.)

Sexual maturation of Atlantic salmon males is marked by dramatic endocrine changes and rapid growth of the testes, resulting in an increase in the gonad somatic index (GSI). We examined the association of gonadal growth with serum sex steroids, as well as pituitary and testicular gene expression levels, which were assessed with a DNA oligonucleotide microarray. The testes transcriptome was stable in males with a GSI < 0.08% despite the large difference between the smallest and the largest gonads. Fish with a GSI ≥ 0.23% had 7-17 times higher serum levels of five male steroids and a 2-fold increase in progesterone, without a change in cortisol and related steroids. The pituitary transcriptome showed an upregulation of the hormone-coding genes that control reproduction and behavior, and structural rearrangement was indicated by the genes involved in synaptic transmission and the differentiation of neurons. The observed changes in the abundance of testicular transcripts were caused by the regulation of transcription and/or disproportional growth, with a greater increase in the germinative compartment. As these factors could not be separated, the transcriptome results are presented as higher or lower specific activities (HSA and LSA). LSA was observed in 4268 genes, including many genes involved in various immune responses and developmental processes. LSA also included genes with roles in female reproduction, germinal cell maintenance and gonad development, responses to endocrine and neural regulation, and the biosynthesis of sex steroids. Two functional groups prevailed among HSA: structure and activity of the cilia (95 genes) and meiosis (34 genes). The puberty of A. salmon testis is marked by the predominance of spermatogenesis, which displaces other processes; masculinization; and the weakening of external regulation. Results confirmed the known roles of many genes involved in reproduction and pointed to uncharacterized genes that deserve attention as possible regulators of sexual maturation.

Minor impact of probiotic bacteria and egg white on Tenebrio molitor growth, microbial composition, and pathogen infection

The industrial rearing of the yellow mealworm (Tenebrio molitor) for feed and food purposes on agricultural by-products may expose larvae and adults to entomopathogens used as biocontrol agents in crop production. Bacterial spores/toxins or fungal conidia from species such as Bacillus thuringiensis or Metarhizium brunneum could affect the survival and growth of insects. Therefore, the aim of this study was to investigate the potential benefits of a wheat bran diet supplemented with probiotic bacteria and dried egg white on larval development and survival and its effects on the gut microbiome composition. Two probiotic bacterial species, Pediococcus pentosaceus KVL B19-01 and Lactiplantibacillus plantarum WJB, were added to wheat bran feed with and without dried egg white, as an additional protein source, directly from neonate larval hatching until reaching a body mass of 20 mg. Subsequently, larvae from the various diets were exposed for 72 h to B. thuringiensis, M. brunneum, or their combination. Larval survival and growth were recorded for 14 days, and the bacterial microbiota composition was analyzed using 16S rDNA sequencing prior to pathogen exposure and on days 3 and 11 after inoculation with the pathogens. The results showed increased survival for T. molitor larvae reared on feed supplemented with P. pentosaceus in the case of co-infection. Larval growth was also impacted in the co-infection treatment. No significant impact of egg white or of P. pentosaceus on larval growth was recorded, while the addition of Lb. plantarum resulted in a minor increase in individual mass gain compared with infected larvae without the latter probiotic. On day 14, B. thuringiensis was no longer detected and the overall bacterial community composition of the larvae was similar in all treatments. On the other hand, the relative operational taxonomic unit (OTU) abundance was dependent on day, diet, and probiotic. Interestingly, P. pentosaceus was present throughout the experiments, while Lb. plantarum was not found at a detectable level, although its transient presence slightly improved larval performance. Overall, this study confirms the potential benefits of some probiotics during the development of T. molitor while underlining the complexity of the relationship between the host and its microbiome.

Development of Self-Assembled Protein Nanocage Spatially Functionalized with HA Stalk as a Broadly Cross-Reactive Influenza Vaccine Platform

There remains a need for the development of a universal influenza vaccine, as current seasonal influenza vaccines exhibit limited protection against mismatched, mutated, or pandemic influenza viruses. A desirable approach to developing an effective universal influenza vaccine is the incorporation of highly conserved antigens in a multivalent scaffold that enhances their immunogenicity. Here, we develop a broadly cross-reactive influenza vaccine by functionalizing self-assembled protein nanocages (SAPNs) with multiple copies of the hemagglutinin stalk on the outer surface and matrix protein 2 ectodomain on the inner surface. SAPNs were generated by engineering short coiled coils, and the design was simulated by MD GROMACS. Due to the short sequences, off-target immune responses against empty SAPN scaffolds were not seen in immunized mice. Vaccination with the multivalent SAPNs induces high levels of broadly cross-reactive antibodies of only external antigens, demonstrating tight spatial control over the designed antigen placement. This work demonstrates the use of SAPNs as a potential influenza vaccine.

A simple preparation of prestained molecular markers for electrophoresis using inexpensive and readily available proteins

Protein electrophoresis in polyacrylamide gels in the presence of sodium dodecyl sulfate (SDS-PAGE) is one of the most commonly performed procedures in biochemical laboratories. It requires the use of molecular weight (MW) markers as an internal technical control and to determine the migration rate of a particular protein. In this work, we describe a simple method for preparing "homemade" prestained protein markers using readily available cow's milk and chicken egg white proteins without the need of any major protein purification step, and produce prestained MW markers ranging from 19 to 98 kDa.

Pulmonary Administration of the Liposome-Based Adjuvant CAF01: Effect of Surface Charge on Mucosal Adjuvant Function

Mucosal surfaces of the lungs represent a major site of entry for airborne pathogens, and pulmonary administration of vaccines is an attractive strategy to induce protective mucosal immunity in the airways. Recently, we demonstrated the potential of pulmonary vaccination with the tuberculosis subunit antigen H56 adjuvanted with the cationic liposomal adjuvant formulation CAF01, which consists of the cationic lipid dimethyldioctadecylammonium (DDA) bromide and the synthetic cord factor trehalose-6,6'-dibehenate. However, the cationic charge of DDA represents a major safety challenge. Hence, replacing DDA with a safer zwitterionic or anionic phospholipid is an attractive approach to improve vaccine safety, but the effect of liposomal surface charge on the induction of mucosal immunity after airway immunization is poorly understood. Here, we investigated the effect of surface charge by replacing the cationic DDA component of CAF01 with zwitterionic dipalmitoylphosphatidylcholine (DPPC) or anionic dipalmitoylphosphatidylglycerol (DPPG), and we show that charge modification enhances antigen-specific pulmonary T-cell responses against co-formulated H56. We systematically replaced DDA with either DPPC or DPPG and found that these modifications resulted in colloidally stable liposomes that have similar size and morphology to unmodified CAF01. DPPC- or DPPG-modified CAF01 displayed surface charge-dependent protein adsorption and induced slightly higher follicular helper T cells and germinal center B cells in the lung-draining lymph nodes than unmodified CAF01. In addition, modified CAF01 induced significantly higher levels of H56-specific Th17 cells and polyfunctional CD4⁺ T cells in the lungs, as compared to unmodified CAF01. However, the strong H56-specific humoral responses induced by CAF01 in the lungs and spleen were not influenced by surface charge. Hence, these results provide insights into the importance of surface charge for liposomal adjuvant function and can also guide the design of safe pulmonary subunit vaccines against other mucosal pathogens.

Amyloids and their untapped potential as hydrogelators

Amyloid fibrils are cross-β-sheet-rich fibrous aggregates. They were originally identified as disease-associated protein/peptide deposits. The cross-β motif was consequently labelled as an alien and pathogenic fold. Subsequent research revealed that the fibrillar aggregates were benign, and the cytotoxicity in the amyloid diseases was attributed to the pre-fibrillar structures. Research in the past two decades has identified the native functional amyloids in organisms ranging from bacteria to human. The amyloid-like fibrils, therefore, are not necessarily pathogenic, and the cross-β motif is very much native. This premise makes way for the amyloids to be used as biocompatible materials. Many naturally occurring amyloidogenic proteins/peptides or their fragments have been reported in the literature to form hydrogels. Hydrogels constitute one of the most interesting classes of soft materials that find application in diverse fields such as environmental, electronic, and biomedical engineering. Applications of hydrogels in medicine are particularly extensive. Among various classes of peptides that form hydrogels, the potential of amyloids is largely untapped. In this review, we have attempted to compile the literature on amyloid hydrogels and discuss their potential applications.

Chicken Egg White-Advancing from Food to Skin Health Therapy: Optimization of Hydrolysis Condition and Identification of Tyrosinase Inhibitor Peptides

Active fragments (bioactive peptides) from the chicken egg white proteins were expected to exert tyrosinase inhibitory activities in which skin hyperpigmentation could be prevented. Egg white was hydrolyzed by trypsin, chymotrypsin and the combination of both enzymes. The enzyme treatments achieved >50% degree of hydrolysis (DH) at substrate-to-enzyme (S/E) ratio of 10–30 (w/w) and hydrolysis time of 2–5 h. A crossed D-optimal experimental design was then used to determine the optimal enzyme composition, S/E ratio and hydrolysis time in order to yield hydrolysates with strong monophenolase and diphenolase inhibitory activities. The optimized conditions 55% trypsin, 45% chymotrypsin, S/E 10:1 w/w and 2 h achieved 45.9% monophenolase activity inhibition whereas 100% trypsin, S/E 22.13:1 w/w and 3.18 h achieved 48.1% diphenolase activity inhibition. LC/MS and MS/MS analyses identified the peptide sequences and the subsequent screening had identified 7 peptides (ILELPFASGDLLML, GYSLGNWVCAAK, YFGYTGALRCLV, HIATNAVLFFGR, FMMFESQNKDLLFK, SGALHCLK and YFGYTGALR) as the potential inhibitor peptides. These peptides were able to bind to H85, H94, H259, H263, and H296 (hotspots for active residues) as well as F92, M280 and F292 (stabilizing residues) of tyrosinase based on structure-activity relationship analysis. These findings demonstrated the potential of egg white-derived bioactive peptides as skin health therapy.

Characterization of Hen's Egg White To Use It as a Novel Platform To Culture Three-Dimensional Multicellular Tumor Spheroids

We are standardizing protocols to develop egg white (EW) as a cost-effective platform for culture of three-dimensional (3-D) multicellular tumor spheroids for application in understanding tumor microenvironments and drug screening. In this article, we describe several physical and physiological characteristics of EW to use it as 3-D cell culture platform. Field emission scanning electron microscopy revealed the presence of different microstructures. Hydrodynamic size distribution data indicated nano- and micron-sized particles. Rheological measurements revealed the viscosity and viscoelastic behavior appropriate for maintaining cell viability and supporting 3-D cell growth under high-sheer conditions. It was found that thereis no autofluorescence, a requirement for imparting transparency and for microscopic observations of the spheroids. The EW facilitated the development of 3-D tumor spheroids, with an emphasis of difference in cell proliferation and intercellular cytoskeletal organization between two-dimensional and 3-D spheroid cultures. Put together, EW proves to be a cost-affordable and simple platform for 3-D culture of tumor spheroids.

Duck egg albumen: physicochemical and functional properties as affected by storage and processing

The demand for duck meat and eggs in Asian countries increases every year. Duck egg albumen has become an important ingredient in the food industry alongside its hen counterpart, because of its excellent nutritive and functional properties. The major proteins in duck albumen are ovalbumin, ovomucoid, ovomucin, conalbumin, and lysozyme. Comparing with hen albumen, lower contents of ovalbumin, conalbumin, lysozyme and ovoflavoprotein are found in duck albumen. Nevertheless, duck albumen shows better gelling and foaming properties than hen albumen. During storage, duck albumen gel properties are enhanced, while foam volume and foam stability are decreased. Moreover, the changes in quality indices of duck egg including the thinning of the albumen, an increase in albumen pH, loss of water and carbon dioxide occur as storage time is increased. Some processes such as alkaline treatment also cause the loss in nutritive value of egg albumen. In this review, the composition and functional properties of duck albumen and how they are affected by processing conditions are also addressed, in comparison with hen albumen. A better understanding of duck egg albumen would be beneficial so that the food processing industry can exploit the potential of this avian protein.

Inhibition of Human Immunodeficiency Type 1 Virus (HIV-1) Life Cycle by Different Egg White Lysozymes

Lysozyme is a relatively small enzyme with different biological activities, which is found in tears, saliva, egg white, and human milk. In the study, the anti-HIV-1 activity of lysozymes purified from quail, Meleagris, and hen egg white has been determined. For this end, a time-of-drug-addition assay was performed to identify the target of anti-HIV-1 agents and for determination of probable anti HIV-1 mechanism of the studied lysozyme, the binding affinity of the lysozymes to the human CD4 receptor was studied by molecular docking method. To define structural differences between studied lysozymes, structural motifs of them were predicted by MEME tool. Quail, hen, and Meleagris lysozymes showed potent anti-HIV-1 activity with EC₅₀ of 7.5, 10, and 55 nM, respectively. The time-of-drug-addition study demonstrated that the inhibitory effect of all purified lysozymes is before HIV-1 infection. The frequency and intensity of CD4 expression in PBMCs decreased in the presence of all mentioned lysozymes. Also, the expression level of C-C chemokine receptor type 5 (CCR5) and chemokine receptor type 4 (CXCR4) on CD4+ T cells was not changed in cells treated with these lysozymes. The results of in silico study confirmed that the binding energy of quail lysozyme with CD4 was more than that of other studied lysozymes. The results revealed that these lysozymes restrict HIV-1 attachment to host cell CD4.

Fate of egg proteins during the development of Columba livia domestica embryo

The transfer of egg white into the yolk and consumption of yolk proteins by the embryo are largely unexplored in the pigeon Columba livia domestica. Here, we investigated the route of egg white transfer as well as the degradation and uptake of yolk proteins by the pigeon embryo. Initially, we tested the electrophoretic patterns of proteins in different egg compartments throughout development. Then, we used lysozyme as a reference protein to follow the egg white transfer, and we measured its activity using Micrococcus lysodeikticus as a substrate. Moreover, we determined the general protease activity during different developmental stages in the yolk using casein. Finally, we examined the expression of aminopeptidase-N (APN) and oligopeptide transporter PepT1 genes in the yolk sac membrane (YSM) from incubation day 8 until day 17. Several electrophoretic bands of presumptive egg white proteins appeared in different egg compartments. Also, lysozyme activity was detected chronologically in the egg compartments. It appeared on day 12 in the amniotic and intestinal fluids and on day 14 in the yolk. Moreover, protease activity in the yolk increased significantly on day 14 and thereafter. APN expression was largest on day 8 and reduced generally afterward, whereas PepT1 expression peaked between days 13 and 15 but then reduced substantially. Our results suggest that the egg white proteins move through the amnion and intestine into the yolk where they undergo degradation by the activated proteases. Furthermore, the YSM appears to have a role in protein consumption, and this role decreases toward hatch.

B1 Power Optimization for Chemical Exchange Saturation Transfer Imaging: A Phantom Study Using Egg White for Amide Proton Transfer Imaging Applications in the Human Brain

The chemical exchange saturation transfer (CEST) effect on an egg white (EW) suspension was investigated for optimization of magnetization transfer (MT) power (B_1,rms) and pH dependency with the addition of lactic acid. Applying a higher MT pulse, B_1,rms, Z-spectrum shows higher asymmetry and the magnetisation transfer ratio (MTR)_asym signal increases to around 1–3.5 ppm, indicating a higher CEST effect. Amide proton transfer (APT) at 3.5 ppm shows a signal elevation in MTR_asym with the application of higher B_1,rms power and high pH. In addition, the hydroxyl proton signal in MTR_asym increases as pH is reduced by lactic acid. In Z-spectrum of B_1,rms at 1.0 μT and 2.0 μT, the dependence on CEST effect of amide proton and hydroxyl proton could be observed by using an EW suspension phantom. The CEST MT power was optimized on the EW suspension phantom with pH dependency and further confirmed on volunteers. In addition, APT imaging at 3.5 ppm using B_1,rms at 1.0 μT performed on two human brains with different pathophysiological conditions indicated appropriate ATP effect.

Protein-bound polyphenols create "ghost" band artifacts during chemiluminescence-based antigen detection

Antigen detection during Western blotting commonly utilizes a horseradish peroxidase-coupled secondary antibody and enhanced chemiluminescent substrate. We utilized this technique to examine the impact of green tea-derived polyphenols on the binding of egg white protein-specific IgE antibodies from allergic human plasma to their cognate antigens. Our experiments unexpectedly showed that green tea-derived polyphenols, when stably complexed with egg white proteins, caused “ghost” band formation in the presence of horseradish peroxide. This study suggests that caution should be taken when evaluating polyphenol-bound proteins by enhanced chemiluminescence Western blotting using horseradish peroxidase and demonstrates that protein-bound polyphenols can be a source of “ghost” band artifacts on Western blots.

Novel Adjuvant Based on the Pore-Forming Protein Sticholysin II Encapsulated into Liposomes Effectively Enhances the Antigen-Specific CTL-Mediated Immune Response

Vaccine strategies to enhance CD8⁺ CTL responses remain a current challenge because they should overcome the plasmatic and endosomal membranes for favoring exogenous Ag access to the cytosol of APCs. As a way to avoid this hurdle, sticholysin (St) II, a pore-forming protein from the Caribbean Sea anemone Stichodactyla helianthus, was encapsulated with OVA into liposomes (Lp/OVA/StII) to assess their efficacy to induce a CTL response. OVA-specific CD8⁺ T cells transferred to mice immunized with Lp/OVA/StII experienced a greater expansion than when the recipients were injected with the vesicles without St, mostly exhibiting a memory phenotype. Consequently, Lp/OVA/StII induced a more potent effector function, as shown by CTLs, in vivo assays. Furthermore, treatment of E.G7-OVA tumor-bearing mice with Lp/OVA/StII significantly reduced tumor growth being more noticeable in the preventive assay. The contribution of CD4⁺ and CD8⁺ T cells to CTL and antitumor activity, respectively, was elucidated. Interestingly, the irreversibly inactive variant of the StI mutant StI W111C, encapsulated with OVA into Lp, elicited a similar OVA-specific CTL response to that observed with Lp/OVA/StII or vesicles encapsulating recombinant StI or the reversibly inactive StI W111C dimer. These findings suggest the relative independence between StII pore-forming activity and its immunomodulatory properties. In addition, StII-induced in vitro maturation of dendritic cells might be supporting these properties. These results are the first evidence, to our knowledge, that StII, a pore-forming protein from a marine eukaryotic organism, encapsulated into Lp functions as an adjuvant to induce a robust specific CTL response.

Genetic Basis of Salmonella Enteritidis Pathogenesis in Chickens

Salmonella Enteritidis (SE) is the predominant cause of the food-borne salmonellosis in humans, in part because this serotype has the unique ability to contaminate chicken eggs without causing discernible illness in the infected birds. Attempts to develop effective vaccines and eradicate SE from chickens are undermined by significant limitations in our current understanding of the genetic basis of pathogenesis of SE in this reservoir host. In this chapter, we summarize the infection kinetics and provide an overview of the current understanding of genetic factors underlying SE infection in the chicken host. We also discuss the important knowledge gaps that, if addressed, will improve our understanding of the complex biology of SE in young chickens and in egg laying hens.

Heteroprotein complex coacervation: A generic process

Proteins exhibit a rich diversity of functional, physico-chemical and biodegradable properties which makes them appealing for various applications in the food and non-food sectors. Such properties are attributed to their ability to interact and assemble into a diversity of supramolecular structures. The present review addresses the updated research progress in the recent field of complex coacervation made from mixtures of oppositely charged proteins (i.e. heteroprotein systems). First, we describe briefly the main proteins used for heteroprotein coacervation. Then, through some selected examples, we illustrate the particularity and specificity of each heteroprotein system and the requirements that drive optimal assembly into coacervates. Finally, possible and promising applications of heteroprotein coacervates are mentioned.

Magnetic nanoparticles as double-edged swords: concentration-dependent ordering or disordering effects on lysozyme

The study of the interaction of nanoparticles (NPs) with proteins is of great importance due to its relevance in several fields including nano-biosafety, nano-bioscience, nano-biomedicine, and nano-biotechnology.

Chicken Ovotransferrin Variants OTFB and OTFC Harboring Substitution of GAT (Asp) to AAT (Asn) in the Codon 500 and their Antimicrobial Activity

Chicken egg white ovotransferrin (OTF) has been reported to exist in three electrophoretic variants (OTF^A, OTF^B and OTF^C). In this report, we identified a causal polymorphism between the OTF^B and OTF^C variants in Japanese and Taiwanese native chickens and compared the antibacterial activity between these two variants. The cDNA sequence analyses from Satsumadori oviducts revealed that three non-synonymous SNPs T1809G (Ser52Ala), A2258G (Ile96Val) and G7823A (Asp500Asn) corresponded to the OTF electrophoretic phenotypes. Of the three SNPs, the G7823A mutation perfectly corresponded to the electrophoretic phenotypes OTF^B (G/G, Asp500Asp), OTF^B/C (G/A, Asp500Asn) and OTF^C (A/A, Asn500Asn) in three chicken populations. The variants OTF^B and OTF^C exhibited similar antibacterial potency against Gram-positive and Gram-negative bacteria. This study provides, for the first time, molecular information on polymorphism of OTF^B and OTF^C variants of chicken ovotransferrin and its effect on the antimicrobial activity of the respective variants.

Identification of TENP as the Gene Encoding Chicken Egg White Ovoglobulin G2 and Demonstration of Its High Genetic Variability in Chickens

Ovoglobulin G2 (G2) has long been known as a major protein constituent of chicken egg white. However, little is known about the biochemical properties and biological functions of G2 because the gene encoding G2 has not been identified. Therefore, the identification of the gene encoding G2 and an analysis of its genetic variability is an important step toward the goal of understanding the biological functions of the G2 protein and its utility in poultry production. To identify and characterize the gene encoding G2, we separated G2 from egg white using electrophoresis on a non-denaturing polyacrylamide gel. Two polymorphic forms of G2 protein (G2^A and G2^B), with different mobilities (fast and slow respectively), were detected by staining. The protein band corresponding to G2^B was electro-eluted from the native gel, re-electrophoresed under denaturing conditions and its N-terminal sequence was determined by Edman degradation following transfer onto a membrane. Sequencing of the 47 kDa G2^B band revealed it to be identical to TENP (transiently expressed in neural precursors), also known as BPI fold-containing family B, member 2 (BPIFB2), a protein with strong homology to a bacterial permeability-increasing protein family (BPI) in mammals. Full-length chicken TENP cDNA sequences were determined for 78 individuals across 29 chicken breeds, lines, and populations, and consequently eleven non-synonymous substitutions were detected in the coding region. Of the eleven non-synonymous substitutions, A329G leading to Arg110Gln was completely associated with the noted differential electrophoretic mobility of G2. Specifically G2^B, with a slower mobility is encoded by A329 (Arg110), whereas G2^A, with a faster mobility, is encoded by G329 (Gln110). The sequence data, derived from the coding region, also revealed that the gene encoding G2 demonstrates significant genetic variability across different chicken breeds/lines/populations. These variants, and how they correlate with egg white properties, may allow us to understand further G2’s functions.

Antigen delivery via hydrophilic PEG-b-PAGE-b-PLGA nanoparticles boosts vaccination induced T cell immunity

Here, we evaluate the use of hydrophilic PEG-b-PAGE-b-PLGA (PPP) for the preparation of antigen loaded nanoparticles (NPs) as a platform for prophylactic vaccination. To investigate the suitability of PPP-NPs for antigen delivery, we used the double emulsion evaporation technique to prepare NPs of different sizes, antigen-loading efficiencies and -release kinetics for the model antigen Ovalbumin (OVA). Prior to applying the PPP-NPs in biological in vitro or in vivo models, all materials were tested for absence of cytotoxicity and endotoxins. While the uptake of NPs in antigen presenting cells was size but not polymer dependent, the efficiency of cross presentation of NP-associated antigen on MHC I molecules for CD8 T cell activation depended on the polymer type. T cell activation by antigen-presenting cells was significantly increased in vitro if antigen was delivered via PPP NPs compared to PLGA NPs or soluble OVA, although antigen content was the same in all tested formulations. Subcutaneous application of PPP-OVA-NPs even without adjuvants led to generation of potent CD8 T cell-mediated OVA-specific cytotoxicity in vivo that was more pronounced than after application of OVA alone or PLGA-OVA-NPs. Our data suggest that PPP-NPs can serve as platform for antigen-delivery in future vaccination formulations. Although PPP-NPs already bear intrinsic adjuvant-function, the complementation with TLR ligands loaded inside NPs may further strengthen the immune response to a point, where it might be possible to use it as a therapeutic vaccine to break immune tolerance in chronic disease states.

Germline Modification and Engineering in Avian Species

Production of genome-edited animals using germline-competent cells and genetic modification tools has provided opportunities for investigation of biological mechanisms in various organisms. The recently reported programmed genome editing technology that can induce gene modification at a target locus in an efficient and precise manner facilitates establishment of animal models. In this regard, the demand for genome-edited avian species, which are some of the most suitable model animals due to their unique embryonic development, has also increased. Furthermore, germline chimera production through long-term culture of chicken primordial germ cells (PGCs) has facilitated research on production of genome-edited chickens. Thus, use of avian germline modification is promising for development of novel avian models for research of disease control and various biological mechanisms. Here, we discuss recent progress in genome modification technology in avian species and its applications and future strategies.

Effects of experimentally increased in ovo lysozyme on egg hatchability, chicks complement activity, and phenotype in a precocial bird

In birds, spectrum of egg white proteins deposited into the egg during its formation are thought to be essential maternal effects. Particularly, egg white lysozyme (LSM), exhibiting great between and within species variability, is considered to be essential for developing avian embryos due to its physiological, antimicrobial, and innate immune defense functions. However, there have been few studies investigating effects of LSM on early post-hatching phenotype, despite its broad physiological and protective role during embryogenesis. Here, we test how experimentally increased concentrations of egg white LSM affect hatchability in Japanese quail (Coturnix japonica) and chick phenotype immediately after hatching (particularly body weight, tarsus length, plasma LSM concentration, and plasma complement activity). Chicks from eggs with increased LSM concentration displayed reduced tarsus length compared to chicks from control eggs while hatchability, body weight and plasma LSM concentration were unaffected. It is worth noting that no effect of increased in ovo lysozyme on eggs hatchability could be related to pathogen-free environment during artificial incubation of experimental eggs causing minimal pressure on embryo viability. While tangible in vivo mechanisms during avian embryogenesis remain to be tested, our study is the first to document experimentally that egg white LSM appears to have growth-regulation role during embryo development, with possible underlying phenotypic consequences in the early post-hatching period in precocial birds.

Adsorption, aggregation, and desorption of proteins on smectite particles

We report on adsorption of lysozyme (LYS), ovalbumin (OVA), or ovotransferrin (OVT) on particles of a synthetic smectite (synthetic layered aluminosilicate). In our approach we used atomic force microscopy (AFM) and quartz crystal microbalance (QCM) to study the protein-smectite systems in water solutions at pH ranging from 4 to 9. The AFM provided insights into the adhesion forces of protein molecules to the smectite particles, while the QCM measurements yielded information about the amounts of the adsorbed proteins, changes in their structure, and conditions of desorption. The binding of the proteins to the smectite surface was driven mainly by electrostatic interactions, and hence properties of the adsorbed layers were controlled by pH. At high pH values a change in orientation of the adsorbed LYS molecules and a collapse or desorption of OVA layer were observed. Lowering pH to the value ≤ 4 caused LYS to desorb and swelling the adsorbed OVA. The stability of OVT-smectite complexes was found the lowest. OVT revealed a tendency to desorb from the smectite surface at all investigated pH. The minimum desorption rate was observed at pH close to the isoelectric point of the protein, which suggests that nonspecific interactions between OVT and smectite particles significantly contribute to the stability of these complexes.

Characterization and properties of carboxymethyl cellulose hydrogels crosslinked by polyethylene glycol

Novel hydrogels were prepared from carboxymethyl cellulose (CMC) sodium salt by crosslinking with polyethylene glycol diglycidyl ether (PEGDE). The detailed structures of the hydrogels were determined via FTIR and solid-state NMR spectroscopic analyses. Increasing the feed ratio of PEGDE to CMC in the reaction mixture led to an increase in the crosslinking degree, which enhanced the physical strength of the hydrogels. The hydrogels exhibited enzyme degradability, and after 3 days of incubation with cellulase, 62-28 wt% of the CMC in the hydrogel was degraded under the conditions employed in this study. In addition, the hydrogels exhibited protein adsorption and release abilities, and the amounts of proteins adsorbed on the hydrogels and the release profile of the proteins depended on the protein sizes and crosslinking degree of the hydrogels. These unique properties might enable the use of CMC-based hydrogels as drug delivery system carriers for protein-based drugs if the biological safety of the hydrogel can be verified.

Interspecific differences in egg production affect egg trace element concentrations after a coal fly ash spill

In oviparous vertebrates, trace elements transfer from mother to offspring during egg production. For animals that produce eggs slowly, like turtles, the trace element concentration of each egg reflects an integration of dietary and stored accumulation over the duration of vitellogenesis. Because turtles also produce eggs synchronously, all eggs within a clutch should exhibit uniform trace element concentrations. In contrast, for animals that produce eggs in sequence and primarily from current dietary resources, like many birds, the trace element concentrations of eggs should be less uniform within a clutch, and likely reflect short-term changes in dietary exposure. We tested the hypothesis that stinkpot turtle (Sternotherus odoratus) clutches exhibit lower variability and higher repeatability in barium, selenium, strontium, and thallium concentrations than those of tree swallows (Tachycineta bicolor) from a site impacted by a recent coal ash spill. All four trace elements exhibited significantly lower variability and significantly higher repeatability in stinkpot clutches than in swallow clutches. Mean trace element concentrations of stinkpot eggs were also significantly higher than those of swallow eggs although both species feed primarily on aquatic invertebrates. Variability in swallow egg trace element concentrations was partially due to significant laying order effects. Our results support the hypothesis that interspecific variation in the source of resources and in the synchronicity and rate of egg production can lead to interspecific differences in the variability of egg trace element concentrations.

Molecular cloning, genomic structure, and tissue distribution of EW135, a novel chicken egg white protein with group B scavenger receptor cysteine-rich domains

Approximately 80 proteins are reported to be present in chicken egg white. The major function of egg white proteins isolated so far is to defend the egg yolk against infections. We recently isolated a novel protein termed EW135 from chicken egg white. In this paper, we have determined the complete amino acid sequence of EW135 based on cDNA cloning. EW135 consists of 970 amino acids with a putative signal peptide of 17 amino acids. It is composed exclusively of tandem repeats of nine group B scavenger receptor cysteine-rich (SRCR) domains separated by eight seven-amino acid peptides. The features of consensus sequences found in the group B SRCR domain were well conserved in EW135. The EW135 gene consists of putative 11 exons, with each SRCR domain being encoded by a single exon. Reverse transcription PCR showed that EW135 is expressed in only the oviduct among the 11 types of tissues tested. EW135 is a second soluble protein belonging to the group B SRCR domain superfamily identified in chickens. One of the important functions of proteins belonging to the group B SRCR domain superfamily is to recognize pathogens in innate immunity. It is, therefore, conceivable that EW135 could be involved in host defense in egg white.

Protein charge and mass contribute to the spatio-temporal dynamics of protein-protein interactions in a minimal proteome

We constructed and simulated a "minimal proteome" model using Langevin dynamics. It contains 206 essential protein types that were compiled from the literature. For comparison, we generated six proteomes with randomized concentrations. We found that the net charges and molecular weights of the proteins in the minimal genome are not random. The net charge of a protein decreases linearly with molecular weight, with small proteins being mostly positively charged and large proteins negatively charged. The protein copy numbers in the minimal genome have the tendency to maximize the number of protein-protein interactions in the network. Negatively charged proteins that tend to have larger sizes can provide a large collision cross-section allowing them to interact with other proteins; on the other hand, the smaller positively charged proteins could have higher diffusion speed and are more likely to collide with other proteins. Proteomes with random charge/mass populations form less stable clusters than those with experimental protein copy numbers. Our study suggests that "proper" populations of negatively and positively charged proteins are important for maintaining a protein-protein interaction network in a proteome. It is interesting to note that the minimal genome model based on the charge and mass of Escherichia coli may have a larger protein-protein interaction network than that based on the lower organism Mycoplasma pneumoniae.

A novel SNP marker of ovalbumin gene in association with duck hatchability

Our previous transcriptome analysis using a cDNA microarray identified differentially-expressed transcripts in Tsaiya ducks (Anas platyrhynchos); we concluded that the ovalbumin gene might be involved in duck hatchability. In the present study, associations of single nucleotide polymorphism (SNP) genotypes of the duck ovalbumin gene with hatchability were investigated. To confirm the cDNA microarray analysis, real-time polymerase chain reaction (PCR) and Western blot analysis were used to validate ovalbumin gene expression. The messenger RNA and protein expression of the ovalbumin gene were higher (P < 0.05) in the low-hatchability group (1.00 ± 0.19; 30.36 ± 3.51 arbitrary units) than in high-hatchability counterparts (0.56 ± 0.07; 8.53 ± 2.97 arbitrary units), consistent with the previous cDNA microarray analysis. The PCR products (506 base pairs) of ovalbumin gene amplified by the primer pair of TovaF and TovaR from the genomic DNA templates of 10 ducks were sequenced and a g.385 C>T SNP site in the 506-base pair sequence of the ovalbumin gene identified. Genotyping of SNP of 187 ducks was then carried out by PCR restriction fragment length polymorphism and minisequencing methods. Based on SNP genotypes of the duck ovalbumin gene, there were three types: CC, TT, and CT. Birds with the CC and TT genotypes had higher hatchability (79.59 ± 3.40, 76.35 ± 1.77) (P < 0.05) than those with a CT genotype (65.77 ± 2.07). In conclusion, the ovalbumin gene was an important candidate gene that can be used for marker-assisted selection to increase hatchability in Tsaiya ducks.

Comparative proteomic analysis of egg white proteins under various storage temperatures

Although the effect of storage temperature was suggested to be a more important factor than that of storage time on changes in unfertilized egg white proteins, no comprehensive analysis of the thermally induced egg white protein changes was carried out. This study presents a proteomic analysis of the changes in unfertilized egg white proteins after 15 days of storage at 4, 20, and 37 °C. Using two-dimensional electrophoresis followed by MALDI-TOF MS/MS, 32 protein spots representing 8 proteins were identified with significant differences in abundance when stored at different temperatures. An accelerated degradation of ovalbumin, possibly resulting from the reduction of antiprotease, was observed after the storage at higher temperature. In addition, an increase in the formation of ovalbumin complexes and a decrease in lipocalin family proteins were detected with increasing storage temperature, which may indicate a thermally promoted change in chicken eggs. The decrease of clusterin during the high-temperature storage was suggested to be an effective biomarker for egg quality evaluation. These findings will give insight into the effects of storage temperature on changes in unfertilized egg white proteins during storage and provide a better understanding of the thermally induced biochemical changes that may affect the egg deteriorative process.