Molecular cloning, expression and phylogenetic analyses of parvalbumin in tilapia, Oreochromis mossambicus

Oncomodulin: The Enigmatic Parvalbumin Protein

EF-hand Ca²⁺-binding protein family members, α- and β-parvalbumins have been studied for decades. Yet, considerable information is lacking distinguishing functional differences between mammalian α-parvalbumin (PVALB) and oncomodulin (OCM), a branded β-parvalbumin. Herein, we provide an overview detailing the current body of work centered around OCM as an EF-Hand Ca²⁺-binding protein and describe potential mechanisms of OCM function within the inner ear and immune cells. Additionally, we posit that OCM is evolutionarily distinct from PVALB and most other β-parvalbumins. This review summarizes recent studies pertaining to the function of OCM and emphasizes OCM as a parvalbumin possessing a unique cell and tissue distribution, Ca²⁺ buffering capacity and phylogenetic origin.

Tropomyosin from tilapia (Oreochromis mossambicus) as an allergen

BACKGROUND

Tilapia is among the most common fresh water fish species raised by fish farms and can cause allergic reactions upon ingestion.

OBJECTIVE

To investigate important allergens in Tilapia (Oreochromis mossambicus).

METHODS

Allergens were detected using immunoblotting. An important allergen was purified to homogeneity by reversed-phase High Pressure Liquid Chromatography and characterized by enzyme linked immunosorbent assay (ELISA), competitive ELISA, Mass spectrometry (MS), circular dichroism measurements and differential scanning calorimetry.

RESULTS

By immunoblotting using sera from 10 patients with confirmed tilapia allergy, we identified a number of allergens with apparent molecular weights 114 to 17 kD. All patients produced IgE against a 32 kD allergen, Ore m 4, which was identified by MS as tropomyosin (TM). IgE binding of the pure protein was confirmed by immunoblotting, ELISA and ELISA inhibition. cDNA from tilapia tropomyosin (TM) was sequenced and compared with TMs from other species. The tilapia TM showed 53.5% homology to TM from shrimp. Homology was much higher to human TM isoform 5 (87.7%).

CONCLUSION AND CLINICAL RELEVANCE

TMs are the major allergens in allergy to crustaceans. Auto-antibodies against human TM isoform 5 have been implicated as a causative agent in inflammatory bowel disease (IBD). Intriguingly, six of the 10 tilapia allergic patients had also been diagnosed with IBD, corroborating a connection between allergy and IBD. To our knowledge, this is the first report of tropomyosin from vertebrates as an allergen.

Purification and characterization of parvalbumins, the major allergens in red stingray (Dasyatis akajei)

Fish has received increasing attention because it induces IgE-mediated food allergy. Parvalbumin (PV) represents the major allergen of fish, and IgE cross-reactivity to PV in various teleost fish species has been shown, while little information is available about allergens in elasmobranch fish. In this study, two PV isoforms (named as PV-I and PV-II) from red stingray (Dasyatis akajei) were purified to homogeneity by a series of procedures including ammonium sulfate precipitation and column chromatographies of DEAE-Sepharose and Sephacryl S-200. Purified PVs revealed a single band on tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular masses of PV-I and PV-II were 12.29 and 11.95 kDa, respectively, as determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Western blot using antifrog PV monoclonal antibody (PARV-19) showed positive reactions to the two proteins, confirming that they were PVs, although their immunological reactivities were weaker than those of PV from silver carp. The N-terminal amino acid sequence of PV-I was determined, and comparison with PVs from other fish species showed low homology between teleost and elasmobranch fish. The isoelectric points of PV-I and PV-II were 5.4 and 5.0, respectively, as determined by two-dimensional electrophoresis (2-DE), suggesting that both isoforms belong to the α-group. IgE immunoblotting analysis showed that sera from fish-allergic patients reacted to both PV-I and PV-II from red stingray. Thermal stability revealed that PV-I easily formed oligomers than PV-II, which might contribute to the maintenance of its allerginicity during heat processing.

Complete mitochondrial DNA sequences of the Nile tilapia (Oreochromis niloticus) and Blue tilapia (Oreochromis aureus): genome characterization and phylogeny applications

Cichlid fishes have played an important role in evolutionary biology and aquaculture industry. Nile tilapia (Oreochromis niloticus), blue tilapia (Oreochromis aureus) and Mozambique tilapia (Oreochromis mossambicus), the useful models in studying evolutionary biology within Cichlid fishes, are also mainly cultured species in aquaculture with great economic importance. In this paper, the complete nucleotide sequence of the mitochondrial genome for O. niloticus and O. aureus were determined and phylogenetic analyses from mitochondrial protein-coding genes were conducted to explore their phylogenetic relationship within Cichlids. The mitogenome is 16,625 bp for O. niloticus and 16,628 bp for O. aureus, containing the same gene order and an identical number of genes or regions with the other Cichlid fishes, including 13 protein-coding genes, two rRNA genes, 22 tRNA genes and one putative control region. Phylogenetic analyses using three different computational algorithms (maximum parsimony, maximum likelihood and Bayesian method) show O. niloticus and O. mossambicus are closely related, and O. aureus has remotely phylogenetic relationship from above two fishes.

Purification and characterization of parvalbumins from silver carp (Hypophthalmichthy molitrix)

BACKGROUND

As the largest producer and consumer of freshwater fish in the world, many people suffer from allergy for consuming freshwater fish in China. However, the allergen profiles of freshwater fish are rarely known.

RESULTS

Parvalbumins (PVs) from the white muscle of silver carp (Hypophthalmichthy molitrix) were purified by ammonium sulfate fractionation and column chromatography including DEAE-Sepharose and Superdex 75. Three PV isoforms-PV-I, PV-II, and PV-III-were obtained and their molecular masses as estimated by tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis were 12, 11, and 14 kDa, respectively. All the PVs could be detected by anti-frog PV monoclonal antibody. PV-I and PV-II were quite possibly glycoproteins, while PV-III was not glycosylated, as analyzed by periodic acid-Schiff (PAS) staining. Thermal stability revealed that PV-I and PV-II easily formed polymers, while these proteins were stable in a pH range of 4.0-10.0. A PV gene encoding 110 amino acid residues was cloned and it revealed high identity with PVs from other species of fish.

CONCLUSION

Three isotypes of PV were purified to homogeneity and one distinct PV gene was cloned in silver carp white muscle.

Characterization, evolution and tissue-specific expression of AmphiCalbin, a novel gene encoding EF-hand calcium-binding protein in amphioxus Branchiostoma belcheri

An amphioxus full-length cDNA, AmphiCalbin, encoding a novel EF-hand calcium-binding protein (EFCaBP), was isolated from the gut cDNA library of amphioxus Branchiostoma belcheri. It consists of 1321 bp with a 636 bp open reading frame encoding a protein of 211 amino acids with a molecular mass of approximately 24.5 kDa. The phylogenetic analysis offers two interesting inferences. First, AmphiCalbin clusters with a group of unnamed EFCaBPs that are differentiated from other identified EFCaBPs. Second, AmphiCalbin falls at the base of the vertebrate unnamed EFCaBPs clade, probably representing their prototype. This is also corroborated by the fact that AmphiCalbin has an exon-intron organization identical to that of vertebrate unnamed EFCaBP genes. Both tissue-section in situ hybridization and whole-mount in situ hybridization prove a tissue-specific expression pattern of AmphiCalbin, with high levels of expression in the digestive system and gonads. It is proposed that AmphiCalbin might play a role in the digestive system and gonads. These observations lay the foundation for further understanding of the function of the unnamed EFCaBPs.