Expression of ayu (Plecoglossus altivelis) Pit-1 in Escherichia coli: its purification and immunohistochemical detection using monoclonal antibody

Peptide Scanning-assisted Identification of a Monoclonal Antibody-recognized Linear B-cell Epitope

The identification of an antigenic epitope by the immune system allows for the understanding of the protective mechanism of neutralizing antibodies that may facilitate the development of vaccines and peptide drugs. Peptide scanning is a simple and efficient method that straightforwardly maps the linear epitope recognized by a monoclonal antibody (mAb). Here, the authors present an epitope determination methodology involving serially truncated recombinant proteins, synthetic peptide design, and dot-blot hybridization for the antigenic recognition of nervous necrosis virus coat protein using a neutralizing mAb. This technique relies on the dot-blot hybridization of synthetic peptides and mAbs on a polyvinylidene fluoride (PVDF) membrane. The minimum antigenic region of a viral coat protein recognized by the RG-M56 mAb can be narrowed down by step-by-step trimmed peptide mapping onto a 6-mer peptide epitope. In addition, alanine scanning mutagenesis and residue substitution can be performed to characterize the binding significance of each amino acid residue making up the epitope. The residues flanking the epitope site were found to play critical roles in peptide conformation regulation. The identified epitope peptide may be used to form crystals of epitope peptide-antibody complexes for an x-ray diffraction study and functional competition, or for therapeutics.

Characterization of transactivation domain and developmental expression of pituitary specific transcription factor, Pit-1 of ayu (Plecoglossus altivelis)

Pit-1 is a pituitary-specific transcription factor, which regulates the expression of growth hormone, prolactin, and thyroid stimulating hormone-beta genes. We previously reported the expression of a Pit-1 gene from ayu (Plecoglossus altivelis), which is an important cultivated food fish in Taiwan and Japan. Comparison of ayu Pit-1 with that of salmon, turkey, and rodent, revealed that the Pit-1 structure is highly conserved through vertebrates, especially in POU-specific and POU-homeo domains. The variation among fish, bird, and mammal are mainly found in transactivation domain by alternative splicing and initiation. Three insertions were found. The gamma-insert in fish Pit-1 is homologous to the exon 2a of avian Pit-1, which is not found in mammals. The beta-insert of fish Pit-1 is homologous to the 28 amino acids (a.a.) and 26 a.a. insert of avian Pit-1 beta(*) and mammalian Pit-1 beta, respectively. An additional similarity was noticed between fish and bird, as both of them contain 7 a.a. insert that is not present in mammalian Pit-1. By site directed mutagenesis, we demonstrated that the beta, gamma, and the 7 a.a. inserts of ayu Pit-1 are critical for activation of zebrafish growth hormone promoter. The ayu Pit-1 protein was found to be expressed specifically in pituitary gland, and its mRNA was first detected at embryonic day 4, significantly increased at embryonic day 5, then sustained to time of hatching at day 8.

Molecular cloning and developmental expression of zinc finger transcription factor MTF-1 gene in zebrafish, Danio rerio

Metal-responsive transcription factor, MTF-1 is a zinc finger protein, shown to be essential for embryonic development. Homozygous knockout mouse embryos for MTF-1 die in utero at day 14 of gestation, due to liver decay. In the present study, we report the complete nucleotide sequence of cDNA encoding zebrafish MTF-1 and the amino acid sequence similarity with that of mouse, human, fish and Drosophila. The size of the zebrafish MTF-1 cDNA is 3,379 bp and the coding region (1,779 bp) encodes a polypeptide of 593 amino acids. The putative zinc finger and transactivation domains comprised by zebrafish MTF-1 were also determined. The zebrafish MTF-1 shows high identity of 97, 93, 93 and 67% in the DNA binding zinc finger domain and 51, 44, 48 and 20% overall identity with fugu, human, mouse and Drosophila, respectively. RT-PCR results show the maternal expression of MTF-1 transcripts. The pattern of MTF-1 gene expression during embryonic and early larval development was studied by whole-mount in situ hybridization using DIG-labeled anti-sense RNA probe. Stronger and ubiquitous expression was observed during the embryonic stages whereas, specific expression, especially in the neural parts, was observed throughout the stages studied after hatching.