Change in glycosylation of chicken transferrin glycans biosynthesized during embryogenesis and primary culture of embryo hepatocytes

Developmental Changes of Duckling Liver and Isolation of Primary Hepatocytes

The liver is the main site of fat synthesis and plays an important role in the study of fat deposition in poultry. In this study, we investigated the developmental changes of duckling livers and isolated primary duck hepatocytes. Firstly, we observed morphological changes in duckling livers from the embryonic period to the first week after hatching. Liver weight increased with age. Hematoxylin-eosin and Oil Red O staining analyses showed that hepatic lipids increased gradually during the embryonic period and declined post-hatching. Liver samples were collected from 21-day-old duck embryos for hepatocyte isolation. The hepatocytes showed limited self-renewal and proliferative ability and were maintained in culture for up to 7 days. Typical parenchymal morphology, with a characteristic polygonal shape, appeared after two days of culture. Periodic acid-Schiff (PAS) staining analysis confirmed the characteristics of duck embryo hepatocytes. PCR analysis showed that these cells from duck embryos expressed the liver cell markers ALB and CD36. Immunohistochemical staining and immunofluorescence analysis also confirmed ALB and CK18 expression. Our findings provide a novel insight regarding in vitro cell culture and the characteristics of hepatocytes from avian species, which could enable further studies concerning specific research on duck lipid metabolism.

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.

The Nutraceutical Properties of Ovotransferrin and Its Potential Utilization as a Functional Food

Ovotransferrin or conalbumin belong to the transferrin protein family and is endowed with both iron-transfer and protective activities. In addition to its well-known antibacterial properties, ovotransferrin displays other protective roles similar to those already ascertained for the homologous mammalian lactoferrin. These additional functions, in many cases not directly related to iron binding, are also displayed by the peptides derived from partial hydrolysis of ovotransferrin, suggesting a direct relationship between egg consumption and human health.

Comparison of chicken and pheasant ovotransferrin N-glycoforms via electrospray ionization mass spectrometry and liquid chromatography coupled with mass spectrometry

Species-specific ovotransferrin features a highly conservative protein sequence, but it varies in the structure of the attached oligosaccharides, which may contribute to the differences observed in its bioactivity and nutritional value. Herein, chicken ovotransferrin (COT) and pheasant ovotransferrin (POT) isolated by repeated ethanol precipitation of egg white were digested with peptide N-glycosidase F to release N-glycans. The obtained N-glyans were isotopically labeled with aniline and analyzed via electrospray ionization mass spectrometry and online hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry (HILIC-MS/MS). Relative quantitation based on isotopic aniline labeling and HILIC-MS/MS analysis revealed in detail the conspicuous difference between COT and POT in the abundance of their N-glycan compositions and isomers. In total, 16 COT N-glycans were observed, including 1 core structure (3.18%), 3 hybrid type (5.42%), and 12 complex type (91.40%), whereas 21 POT N-glycans were found, including 1 truncated structure (1.88%), 1 core structure (6.26%), 3 high mannose type (5.20%), 6 hybrid type (19.14%), and 10 complex type (67.52%). To our knowledge, this study is the first qualitative and quantitative comparison of COT and POT N-glycosylation patterns. These results suggest that POT has a different glycosylation pattern compared to that of COT and thus the effect of its glycosylation pattern on its bioactivity is worthy of further exploration.

Physiological roles of ovotransferrin

BACKGROUND

Ovotransferrin is an iron-binding glycoprotein, found in avian egg white and in avian serum, belonging to the family of transferrin iron-binding glycoproteins. All transferrins show high sequence homology. In mammals are presents two different soluble glycoproteins with different functions: i) serum transferrin that is present in plasma and committed to iron transport and iron delivery to cells and ii) lactoferrin that is present in extracellular fluids and in specific granules of polymorphonuclear lymphocytes and committed to the so-called natural immunity. To the contrary, in birds, ovotransferrin remained the only soluble glycoprotein of the transferrin family present both in plasma and egg white.

SCOPE OF REVIEW

Substantial experimental evidences are summarized, illustrating the multiple physiological roles of ovotransferrin in an attempt to overcome the common belief that ovotransferrin is a protein dedicated only to iron transport and to iron withholding antibacterial activity.

MAJOR CONCLUSIONS

Similarly to the better known family member protein lactoferrin, ovotransferrin appears to be a multi-functional protein with a major role in avian natural immunity.

GENERAL SIGNIFICANCE

Biotechnological applications of ovotransferrin and ovotransferrin-related peptides could be considered in the near future, stimulating further research on this remarkable protein. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.

Molecular evolution of the transferrin family and associated receptors

BACKGROUND

In vertebrates, serum transferrins are essential iron transporters that have bind and release Fe(III) in response to receptor binding and changes in pH. Some family members such as lactoferrin and melanotransferrin can also bind iron while others have lost this ability and have gained other functions, e.g., inhibitor of carbonic anhydrase (mammals), saxiphilin (frogs) and otolith matrix protein 1 (fish).

SCOPE OF REVIEW

This article provides an overview of the known transferrin family members and their associated receptors and interacting partners.

MAJOR CONCLUSIONS

The number of transferrin genes has proliferated as a result of multiple duplication events, and the resulting paralogs have developed a wide array of new functions. Some homologs in the most primitive metazoan groups resemble both serum and melanotransferrins, but the major yolk proteins show considerable divergence from the rest of the family. Among the transferrin receptors, the lack of TFR2 in birds and reptiles, and the lack of any TFR homologs among the insects draw attention to the differences in iron transport and regulation in those groups.

GENERAL SIGNIFICANCE

The transferrin family members are important because of their clinical significance, interesting biochemical properties, and evolutionary history. More work is needed to better understand the functions and evolution of the non-vertebrate family members. This article is part of a Special Issue entitled Molecular Mechanisms of Iron Transport and Disorders.

Carbohydrate biomarkers for future disease detection and treatment

Carbohydrates are considered as one of the most important classes of biomarkers for cell types, disease states, protein functions, and developmental states. Carbohydrate "binders" that can specifically recognize a carbohydrate biomarker can be used for developing novel types of site specific delivery methods and imaging agents. In this review, we present selected examples of important carbohydrate biomarkers and how they can be targeted for the development of therapeutic and diagnostic agents. Examples are arranged based on disease categories including (1) infectious diseases, (2) cancer, (3) inflammation and immune responses, (4) signal transduction, (5) stem cell transformation, (6) embryo development, and (7) cardiovascular diseases, though some issues cross therapeutic boundaries.

Ion mobility-mass spectrometry analysis of isomeric carbohydrate precursor ions

The rapid separation of isomeric precursor ions of oligosaccharides prior to their analysis by mass spectrometry to the nth power (MS(n)) was demonstrated using an ambient pressure ion mobility spectrometer (IMS) interfaced with a quadrupole ion trap. Separations were not limited to specific types of isomers; representative isomers differing solely in the stereochemistry of sugars, in their anomeric configurations, and in their overall branching patterns and linkage positions could be resolved in the millisecond time frame. Physical separation of precursor ions permitted independent mass spectra of individual oligosaccharide isomers to be acquired to at least MS(3), the number of stages of dissociation limited only practically by the abundance of specific product ions. IMS-MS(n) analysis was particularly valuable in the evaluation of isomeric oligosaccharides that yielded identical sets of product ions in tandem mass spectrometry experiments, revealing pairs of isomers that would otherwise not be known to be present in a mixture if evaluated solely by MS dissociation methods alone. A practical example of IMS-MS(n) analysis of a set of isomers included within a single high-performance liquid chromatography fraction of oligosaccharides released from bovine submaxillary mucin is described.

Evaluation of the prophylactic use of ovotransferrin against chlamydiosis in SPF turkeys

Chlamydophila (C.) psittaci infections are highly prevalent in turkeys and the economical and public health importance of these infections has been recognized since 1950. As there are no vaccines, antibiotic treatment (tetracylines, enrofloxacine) is often needed to allow marketing of poultry. In this study, we explored the use of ovotransferrin (ovoTF), a natural anti-microbial protein, in preventing an experimental C. psittaci infection in specific pathogen free (SPF) turkeys. Turkeys were treated with aerosolized ovoTF prior to the infection. Groups 1 and 2 received a single dose of 10 and 5 mg ovoTF per turkey, respectively. Group 3 received a daily dose of 5mg ovoTF per turkey during 12 days. Group 4 served as untreated, infected control group. Turkeys were aerosol infected using 10(6) TCID(50) of the virulent C. psittaci serovar/genotype D strain 92/1293. Birds were monitored (clinical signs, bacterial excretion) during 12 subsequent days before being necropsied. At necropsy, pathology and C. psittaci replication in various tissues was examined. A single dose of 10mg ovoTF and a repeated daily dose of 5mg ovoTF could not prevent the birds from becoming infected with C. psittaci, but they significantly reduced the outcome of the infection. A single dose of 5mg ovoTF had no influence on the outcome of the infection as compared to the non-treated infected controls. Our results demonstrate the anti-chlamydial effect of ovoTF in vivo and present a base for further research on practical applications of ovoTF on turkey farms.

Ovotransferrin expression and release by chicken cell lines infected with Marek's disease virus

Mammals posses both serum transferrin and lactoferrin, whose functions are taken over in birds by ovotransferrin, displaying both iron transport and antibacterial activities. Ovotransferrin also exerts antiviral activity towards Marek's disease virus, an avian member of the herpes family of viruses. This virus infects lymphoid organs and induces the transcription of ovotransferrin in infected chicken embryo fibroblasts. However, it has not yet been established whether ovotransferrin gene transcription is linked to the release of the protein outside the cells or whether ovotransferrin expression and release also occurs in chicken lymphoblastoid cells in which the Marek's disease viral genome is integrated. Our results indicate that both serum and egg-white isoforms of ovotransferrin are expressed and released in the supernatants of chicken embryo fibroblast and lymphoblastoid cells in the absence of infection. Viral infection of chicken embryo fibroblasts caused a slight increase of ovotransferrin release, whereas viral reinfection of lymphoblastoid cells caused a remarkable ovotransferrin release in a virus concentration-dependent manner. These findings suggest that ovotransferrin release in vivo may play a crucial role in protecting the whole organism from viral infection spreading, and support the hypothesis that the antiviral activity of ovotransferrin is an important part of the innate immune response in birds, resembling the antiviral activity of lactoferrin in mammals.

Antiviral activity of ovotransferrin discloses an evolutionary strategy for the defensive activities of lactoferrin

Ovotransferrin (formerly conalbumin) is an iron-binding protein present in birds. It belongs to the transferrin family and shows about 50% sequence homology with mammalian serum transferrin and lactoferrin. This protein has been demonstrated to be capable of delivering iron to cells and of inhibiting bacterial multiplication. However, no antiviral activity has been reported for ovotransferrin, although the antiviral activity of human and bovine lactoferrins against several viruses, including human herpes simplex viruses, has been well established. In this report, the antiviral activity of ovotransferrin towards chicken embryo fibroblast infection by Marek's disease virus (MDV), an avian herpesvirus, was clearly demonstrated. Ovotransferrin was more effective than human and bovine lactoferrins in inhibiting MDV infection and no correlation between antiviral efficacy and iron saturation was found. The observations reported here are of interest from an evolutionary point of view since it is likely that the defensive properties of transferrins appeared early in evolution. In birds, the defensive properties of ovotransferrin remained joined to iron transport functions; in mammals, iron transport functions became peculiar to serum transferrin, and the defensive properties towards infections were optimised in lactoferrin.

Fucose in N-glycans: from plant to man

Fucosylated oligosaccharides occur throughout nature and many of them play a variety of roles in biology, especially in a number of recognition processes. As reviewed here, much of the recent emphasis in the study of the oligosaccharides in mammals has been on their potential medical importance, particularly in inflammation and cancer. Indeed, changes in fucosylation patterns due to different levels of expression of various fucosyltransferases can be used for diagnoses of some diseases and monitoring the success of therapies. In contrast, there are generally at present only limited data on fucosylation in non-mammalian organisms. Here, the state of current knowledge on the fucosylation abilities of plants, insects, snails, lower eukaryotes and prokaryotes will be summarised.

Butyrylcholinesterase is complexed with transferrin in chicken serum

The function of the enzyme butyrylcholinesterase (BChE) both in serum and in brain is unclear. In serum, BChE has been found complexed with several biomedically relevant proteins, with which it could function in concert. Here, the existence of a similar complex formed between BChE and sero-transferrin from adult chicken serum was elucidated. In order to identify both proteins unequivocally, we improved methods to highly purify the 81-kDa BChE and the coisolated 75-kDa transferrin, which then allowed us to tryptically digest and sequence the resulting peptides. The sequences as revealed for BChE peptides were highly identical to mammalian BChEs. A tight complex formation between the two proteins could be established (a) since transferrin is coisolated along with BChE over three steps including procainamide affinity chromatography, while transferrin alone is not bound to this affinity column, and (b) since imunoprecipitation experiments of whole serum with a transferrin-specific antiserum allows us to detect BChE in the precipitate with the BChE-specific monoclonal antibody 7D11. The possible biomedical implications of a complex between transferrin and BChE which here has been shown to exist in chicken serum are briefly discussed.

Rat mammary-gland transferrin: nucleotide sequence, phylogenetic analysis and glycan structure

The complete cDNA for rat mammary-gland transferrin (Tf) has been sequenced and also the native protein isolated from milk in order to analyse the structure of the main glycan variants present. A lactating-rat mammary-gland cDNA library in lambda gt10 was screened with a partial cDNA copy of rat liver Tf and subsequently rescreened with 5' fragments of the longest clones. This produced a 2275 bp insert coding for an open reading frame of 695 amino acid residues. This includes a 19-amino acid signal sequence and the mature protein containing 676 amino acids and one N-glycosylation site in the C-terminal domain at residue 490. Phylogenetic analysis was carried out using 14 translated Tf nucleotide sequences, and the derived evolutionary tree shows that at least three gene duplication events have occurred during Tf evolution, one of which generated the N- and C-terminal domains and occurred before separation of arthropods and chordates. The two halves of human melanotransferrin are more similar to each other than to any other sequence, which contrasts with the pattern shown by the remaining sequences. Native rat milk Tf is separated into four bands on native PAGE that differ only in their sialic acid content: one biantennary glycan is present containing either no sialic acid residues or up to three. The complete structures of the two major variants were determined by methylation, m.s. and 400 MHz 1H-n.m.r. spectroscopy. They contain either one or two neuraminic acid residues (alpha 2-->6)-linked to galactose in conventional biantennary N-acetyl-lactosamine-type glycans. Most contain fucose (alpha 1-->6)-linked to the terminal non-reducing N-acetylglucosamine.