Glucocorticoid receptor and protein/RNA synthesis-dependent mechanisms underlie the control of synaptic plasticity by stress

Learning and memory are exquisitely sensitive to behavioral stress, but the underlying mechanisms are still poorly understood. Because activity-dependent persistent changes in synaptic strength are believed to mediate memory processes in brain areas such as the hippocampus we have examined the means by which stress affects synaptic plasticity in the CA1 region of the hippocampus of anesthetized rats, Inescapable behavioral stress (placement on an elevated platform for 30 min) switched the direction of plasticity, favoring low frequency stimulation-induced decreases in synaptic transmission (long-term depression, LTD), and opposing the induction of long-term potentiation by high frequency stimulation, We have discovered that glucocorticoid receptor activation mediates these effects of stress on LTD and longterm potentiation in a protein synthesis-dependent manner because they were prevented by the glucocorticoid receptor antagonist RU 38486 and the protein synthesis inhibitor emetine. Consistent with this, the ability of exogenously applied corticosterone in non-stressed rats to mimic the effects of stress on synaptic plasticity was also blocked by these agents, The enablement of low frequency stimulation-induced LTD by both stress and exogenous corticosterone was also blocked by the transcription inhibitor actinomycin D, Thus, naturally occurring synaptic plasticity is liable to be reversed in stressful situations via glucocorticoid receptor activation and mechanisms dependent on the synthesis of new protein and RNA, This indicates that the modulation of hippocampus-mediated learning by acute inescapable stress requires glucocorticoid receptor-dependent initiation of transcription and translation.

Male-infant-male interactions in Tibetan macaques

Event-sampling and scans were used for collecting data on male-infant-male triadic interactions, and their effects on member spacing respectively in a group of Macaca thibetana at Mt. Emei in 1989. The group was partially provisioned by human visitors in seasons other than winter, and could be observed closely. In addition, a stable linear male-hierarchy among five males existed for two years since the end of 1987, providing a good social condition for this topic. The triadic interactions were specific to the birth season, and recognized as three types being on a continuum functionally changing from passive ''agonistic buffering'' (4.8%) to active spatial cohesion, which resulted in a significant decline of intermale distances. Positive correlations were documented between the triad initiation rate and the number of females in consort with the males in the mating season (MS), and between the triad reception rate and the number of infants in proximity to the males in the MS when maternal care was significantly reduced. Thus the male's mating effort and kin/sexual selection may deeply be involved in the triad of this species. Considering that the two triad-species, M. sylvanus and M. thibetana, had different levels of paternity, but shared similar foraging conditions, and showed similar intensities of male-infant caretaking, the triad was very likely a byproduct of male-infant caretaking, which was probably shaped to compensate heavy maternal investment to young offspring in harsh conditions. Accordingly, the long-term arguments about the triad in M. sylvanus can be united to a model of the way in which ''male-infant caretaking'' hypothesis works ultimately, and ''regulating social relations'' hypothesis does proximately.

Grass carp reovirus activates RNAi pathway in rare minnow, Gobiocypris rarus

Dicer catalyzes the initiation step of RNA interference (RNAi) which is known to play a significant role in innate immune response to viral infection in many organisms. To study the RNAi-related pathway after virus infection in fish, we identified a partial cDNA sequence of dicer from rare minnow, Gobiocypris rants. Real-time quantitative RT-PCR (qRT-PCR) demonstrated the Dicer transcript level was the highest at zygote stage, decreased at prim-5 stage, and was stable from the protruding mouth to adult stage. Regular RT-PCR analysis showed that the Dicer gene expressed widely in the tested tissues, including brain, gill, heart, intestine, kidney, liver, muscle, ovary, spleen and testis. The expression of Dicer mRNA was significantly increased in the early period of Grass carp reovirus (GCRV) infection, and declined from 24 It post-injection (h p.i.) (P<0.05). The mRNA expression returned to control levels at 48 h p.i. (P>0.05). Under transmission electron microscope, virions were difficulty to find out in 12 h p.i., and virus inclusion bodies and few scattered viral particles were easily visualized from 24 h p.i. to moribund. These results implied GCRV triggered the RNAi pathway in the early stages of infection and perhaps virus inclusion bodies suppressed the antiviral functions of RNAi mechanism. (C) 2009 Published by Elsevier B.V.

Identification of Differentially Expressed Genes Between Cloned and Zygote-Developing Zebrafish (Danio rerio) Embryos at the Dome Stage Using Suppression Subtractive Hybridization

Comparative analyses of differentially expressed genes between somatic cell nuclear transfer (SCNT) embryos and zygote-developing (ZD) embryos are important for understanding the molecular mechanism underlying the reprogramming processes. Herein, we used the suppression subtractive hybridization approach and from more than 2900 clones identified 96 differentially expressed genes between the SCNT and ZD embryos at the dome stage in zebrafish. We report the first database of differentially expressed genes in zebrafish SCNT embryos. Collectively, our findings demonstrate that zebrafish SCNT embryos undergo significant reprogramming processes during the dome stage. However, most differentially expressed genes are down-regulated in SCNT embryos, indicating failure of reprogramming. Based on Ensembl description and Gene Ontology Consortium annotation, the problems of reprogramming at the dome stage may occur during nuclear remodeling, translation initiation, and regulation of the cell cycle. The importance of regulation from recipient oocytes in cloning should not be underestimated in zebrafish.

Bead-probe complex capture a couple of SINE and LINE family from genomes of two closely related species of East Asian cyprinid directly using magnetic separation

Background: Short and long interspersed elements (SINEs and LINEs, respectively), two types of retroposons, are active in shaping the architecture of genomes and powerful tools for studies of phylogeny and population biology. Here we developed special protocol to apply biotin-streptavidin bead system into isolation of interspersed repeated sequences rapidly and efficiently, in which SINEs and LINEs were captured directly from digested genomic DNA by hybridization to bead-probe complex in solution instead of traditional strategy including genomic library construction and screening. Results: A new couple of SINEs and LINEs that shared an almost identical 3'tail was isolated and characterized in silver carp and bighead carp of two closely related species. These SINEs (34 members), designated HAmo SINE family, were little divergent in sequence and flanked by obvious TSD indicated that HAmo SINE was very young family. The copy numbers of this family was estimated to 2 x 10(5) and 1.7 x 10(5) per haploid genome by Real-Time qPCR, respectively. The LINEs, identified as the homologs of LINE2 in other fishes, had a conserved primary sequence and secondary structures of the 3'tail region that was almost identical to that of HAmo SINE. These evidences suggest that HAmo SINEs are active and amplified recently utilizing the enzymatic machinery for retroposition of HAmoL2 through the recognition of higher-order structures of the conserved 42-tail region. We analyzed the possible structures of HAmo SINE that lead to successful amplification in genome and then deduced that HAmo SINE, SmaI SINE and FokI SINE that were similar in sequence each other, were probably generated independently and created by LINE family within the same lineage of a LINE phylogeny in the genomes of different hosts. Conclusion: The presented results show the advantage of the novel method for retroposons isolation and a pair of young SINE family and its partner LINE family in two carp fishes, which strengthened the hypotheses containing the slippage model for initiation of reverse transcription, retropositional parasitism of SINEs on LINEs, the formation of the stem loop structure in 3'tail region of some SINEs and LINEs and the mechanism of template switching in generating new SINE family.

Antimicrobial activity-specific to Gram-negative bacteria and immune modulation-mediated NF-kappa B and Sp1 of a medaka beta-defensin

Defensins are a group of cationic antimicrobial peptides which play an important role in the innate immune system by exerting their antimicrobial activity against pathogens. In this study, we cloned a novel beta-defensin cDNA from medaka (Oryzias latipes) by rapid amplification of cDNA ends (RACE) technique. The full-length cDNA consists of 480 bp, and the open reading frame (CRF) of 189 bp encodes a polypeptide of 63 amino acids (aa) with a predicted molecular weight of 7.44 kDa. Its genomic organization was analyzed, and Southern blot detection confirmed that only one copy of beta-defensin exists in the medaka HNI strain. RT-PCR, Western blot and immunohistochemistry detections showed that the beta-defensin transcript and protein could be detected in eyes, liver, kidney, blood, spleen and gill, and obviously prevalent expression was found in eyes. Antimicrobial activity of the medaka beta-defensin was evaluated, and the antibacterial activity-specific to Gram-negative bacteria was revealed. Furthermore, the lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria, was demonstrated to be able to induce about 13-fol up-regulation of the beta-defensin within first 12 h. In addition, promoter and promoter mutagenesis analysis were performed in the medaka beta-defensin. A proximal 100 base pair(bp) sequence (+26 to -73)and the next 1700 bp sequence (-73 to -1755) were demonstrated to be responsible for the basal promoter activity and for the transcription regulation. Three nuclear factor kappa B (NF-kappa B) cis-elements and a Sp1 cis-element were revealed by mutagenesis analysis to exist in the 5' flanking sequence, and they were confirmed to be responsible for the up-regulation of medaka beta-defensin stimulated by LPS. And, the Sp1 cis-element was further revealed to be related to the basal promoter activity, and transcriptional factor II D (TFIID) was found to be in charge of the gene transcription initiation. All the obtained data suggested that the novel medaka beta-defensin should have antimicrobial activity-specific to Gram-negative bacteria, and the antibacterial immune function should be modulated by NF-kappa B and Sp1. (C) 2008 Elsevier Ltd. All rights reserved.

Functional domains and the antiviral effect of the double-stranded RNA-dependent protein kinase PKR from Paralichthys olivaceus

The double-stranded RNA (dsRNA)-dependent protein kinase PKR is thought to mediate a conserved antiviral pathway by inhibiting viral protein synthesis via the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2 alpha). However, little is known about the data related to the lower vertebrates, including fish. Recently, the identification of PKR-like, or PKZ, has addressed the question of whether there is an orthologous PKR in fish. Here, we identify the first fish PKR gene from the Japanese flounder Paralichthys olivaceus (PoPKR). PoPKR encodes a protein that shows a conserved structure that is characteristic of mammalian PKRs, having both the N-terminal region for dsRNA binding and the C-terminal region for the inhibition of protein translation. The catalytic activity of PoPKR is further evidence that it is required for protein translation inhibition in vitro. PoPKR is constitutively transcribed at low levels and is highly induced after virus infection. Strikingly, PoPKR overexpression increases eIF2 alpha phosphorylation and inhibits the replication of Scophthalmus maximus rhabdovirus (SMRV) in flounder embryonic cells, whereas phosphorylation and antiviral effects are impaired in transfected cells expressing the catalytically inactive PKR-K421R variant, indicating that PoPKR inhibits virus replication by phosphorylating substrate eIF2 alpha. The interaction between PoPKR and eIF2 alpha is demonstrated by coimmunoprecipitation assays, and the transfection of PoPKR-specific short interfering RNA further reveals that the enhanced eIF2 alpha phosphorylation is catalyzed by PoPKR during SMRV infection. The current data provide significant evidence for the existence of a PKR-mediated antiviral pathway in fish and reveal considerable conservation in the functional domains and the antiviral effect of PKR proteins between fish and mammals.

Identification of differentially expressed genes from the cross-subfamily cloned embryos derived from zebrafish nuclei and rare minnow enucleated eggs

Cross-species nuclear transfer (NT) has been used to retain the genetic viability of a species near extinction. However, unlike intra-species NT, most embryos produced by cross-species NT were unable to develop to later stages due to incompatible nucleocytoplasmic interactions between the donor nuclei and the recipient cytoplasm from different species. To study the early nucleocytoplasmic interaction in cross-species NT, two laboratory fish species (zebrafish and rare minnow) from different subfamilies were used to generate cross-subfamily NT embryos in the present study. Suppression subtractive hybridization (SSH) was performed to screen out differentially expressed genes from the forward and reverse subtractive cDNA libraries. After dot blot and real-time PCR analysis, 80 of 500 randomly selective sequences were proven to be differentially expressed in the cloned embryos. Among them, 45 sequences shared high homology with 28 zebrafish known genes, and 35 sequences were corresponding to 22 novel expressed sequence tags (ESTs). Based on functional clustering and literature mining analysis, up-and down-regulated genes in the cross-subfamily cloned embryos were mostly relevant to transcription and translation initiation, cell cycle regulation, protein binding, etc. To our knowledge, this is the first report on the determination of genes involved in the early development of cross-species NT embryos of fish. (C) 2007 Elsevier Inc. All rights reserved.

Gene structure of an antimicrobial peptide from mandarin fish, Siniperca chuatsi (Basilewsky), suggests that moronecidins and pleurocidins belong in one family: the piscidins

The gene of piscidin, an antimicrobial peptide, has been cloned from the mandarin fish, Siniperca chuatsi. From the first transcription initiation site, the mandarin fish piscidin gene extends 1693 nucleotides to the end of the 3' untranslated region and contains four exons and three introns. A predicted 79-residue prepropeptide consists of three domains: a signal peptide (22 aa), a mature peptide (22 aa) and a C-terminal prodomain (35 aa). The shortage of XQQ motif in the prodomain of mandarin fish piscidin and the similar gene structure between moronecidins (piscidins) and pleurocidins may indicate that they are derived from the same ancestor gene. We thus suggest that piscidin should be used as a terminology for these antimicrobial peptides in the future. The mandarin fish piscidin mRNA was abundant in intestine, spleen, pronephros and kidney analysed by real-time polymerase chain reaction. After stimulation with lipopoly saccharides (LPS), a marked increase in transcripts was observed in most tissues, indicating that piscidin is not only a constitutively expressed molecule, but also has an increased response to bacterial infection. The synthetic, amidated mandarin fish piscidin exhibited different antimicrobial activity against different fish bacterial pathogens, especially against species of Aeromonas, which may to certain extent reflect the pathogenicity of these bacteria.

Cloning, characterization and promoter analysis of common carp hairy/Enhancer-of-split-related gene, her6

Some members of hairy/Enhancer-of-split-related gene (HES) family have important effects on axial mesoderm segmentation and the establishment and maintenance of the somite fringe. In fishes. the her6 gene, a member of the HES family, is the homologue Of heS1 in mammals and chicken. In this study, the her6 gene and its full-length cDNA from the common carp (Cyprinus carpio) were isolated and characterized. The genomic sequence of common carp her6 is approximately 1.7 kb. with four exons and three introns, and the full-length cDNA of 1314 bp encodes a Putative polypeptide of 271 amino acids. To analyse the promoter sequence of common carp her6. sequences of various lengths upstream from the transcription initiation site of her6 were fused to enhanced green fluorescent. protein gene (eGFP) and introduced into zebrafish embryos by microinjection to generate transgenic embryos. Our results show that the upstream sequence of 500 bp can direct highly efficient and tissue-specific expression of eGFP in zebrafish embryos. whereas a fragment of 200 bp containing the TATA box and a partial suppressor of hairless paired site sequence (SPS) is not sufficient to drive eGFP expression in zebrafish embryos.

Characterization of an early gene encoding for dUTPase in Rana grylio virus

dUTPase (DUT) is a ubiquitous and important enzyme responsible for regulating levels of dUTP. Here, an iridovirus DUT was identified and characterized from Rana grylio virus (RGV) which is a pathogen agent in pig frog. The DUT encodes a protein of 164aa with a predicted molecular mass of 17.4 kDa, and its transcriptional initiation site was determined by 5'RACE to start from the nucleotide A at 15 nt upstream of the initiation codon ATG. Sequence comparisons and multiple alignments suggested that RGV DUT was quite similar to other identified DUTs that function as homotrimers. Phylogenetic analysis implied that DUT horizontal transfers might have occurred between the vertebrate hosts and iridoviruses. Furthermore, its temporal expression pattern during RGV infection course was characterized by RT-PCR and Western blot analysis. It begins to transcribe and translate as early as 4 h postinfection (p.i.), and remains detectable at 48 h p.i. DUT-EGFP fusion protein was observed in the cytoplasm of pEGFP-N3-Dut transfected EPC cells. Immunofluorescence also confirmed DUT cytoplasm localization in RGV-infected cells. Using drug inhibition analysis by a de novo protein synthesis inhibitor (cycloheximide) and a viral DNA replication inhibitor (cytosine arabinofuranoside), RGV DUT was classified as an early (E) viral gene during the in vitro infection. Moreover, RGV DUT overexpression was shown that there was no effect on RGV replication by viral replication kinetics assay. (c) 2006 Published by Elsevier B.V.

Characterization of the Rana grylio virus 3 beta-hydroxysteroid dehydrogenase and its novel role in suppressing virus-induced cytopathic effect

The 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) isoenzymes play a key role in cellular steroid hormone synthesis. Here, a 3 beta-HSD gene homolog,was cloned from Rana grylio virus (RGV), a member of family Iridoviridae. RGV 3 beta-HSD gene has 1068 bp, encoding a 355 aa predicted protein. Transcription analyses showed that RGV 3 beta-HSD gene was transcribed immediate-early during infection from an initiation site 19 nucleotides upstream of the translation start site. Confocal microscopy revealed that the 3 beta-HSD-EGFP fusion protein was exclusively colocalized with the mitochondria marker (pDsRed2-Mito) in EPC cells. Upon morphological observation and MTT assay, it was revealed that overexpression of RGV 3 beta-HSD in EPC cells could apparently suppress RGV-induced cytopathic effect (CPE). The present studies indicate that the RGV immediate-early 3 beta-HSD gene encodes a mitochondria-localized protein, which has a novel role in suppressing virus-induced CPE. All these suggest that RGV 3 beta-HSD might be a protein involved in host-virus interaction. @ 2006 Elsevier Inc. All rights reserved.

Gene structure of goose-type lysozyme in the mandarin fish Siniperca chuatsi with analysis on the lytic activity of its recombinant in Escherichia coli

A goose-type lysozyme (g-lysozyme) gene has been cloned from the mandarin fish (Siniperca chuatsi), with its recombinant protein expressed in Escherichia coli. From the first transcription initiation site, the mandarin fish g-lysozyme gene extends 1307 nucleotides to the end of the 3' untranslated region, and it contains 5 exons and 4 introns. The open reading frame of the glysozyme transcript has 582 nucleotides which encode a 194 amino acid peptide. The 5' flanking region of mandarin fish glysozyme gene shows several common transcriptional factor binding sites when compared with that from Japanese flounder (Paralichthys olivaceus). The recombinant mandarin fish g-lysozyme was expressed in E. coli by using pET-32a vector, and the purified recombinant g-lysozyme shows lytic activity against Micrococcus lysodeikticus. (c) 2005 Elsevier B.V All rights reserved.

Gene cloning and functional analysis of glycosaminoglycan-degrading enzyme chondroitin AC lyase from Flavobacterium columnare G(4)

The chondroitin AC lyase gene, cslA, was cloned for the first time from the fish bacterial pathogen F. columnare G(4). From the first transcription initiation site, the cslA extends 2620 nucleotides to the end of the 3' region. The open reading frame of cslA transcript has 2286 nucleotides encoding 762 amino acids with a 16 residues long signal peptide at the N-terminus. The gene, cslA was then successfully expressed in Escherichia coli and recombinant chondroitin AC lyase, rChonAC was purified, with its lytic activity analyzed. Zymography analysis copolymerized with chondroitin sulphate revealed the lytic activity of rChonAC and also the crude native ChonAC isolated from periplamic space of cultured F. columnare G(4). The low level of lytic activity observed in crude native ChonAC may be due possibly to the low level of expression of this gene in the cultured condition. The expression and the role of this virulence factor is of interest for further research on the pathogenesis of F. columnare.

De novo RNA synthesis and homology modeling of the classical swine fever virus RNA polymerase

Classical swine fever virus (CSFV) non-structural protein 5B (NS5B) encodes an RNA-dependent RNA polymerase (RdRp), a key enzyme which initiates RNA replication by a de novo mechanism without a primer and is a potential target for anti-virus therapy. We expressed the NS5B protein in Escherichia coli. The rGTP can stimulate de novo initiation of RNA synthesis and mutation of the GDD motif to Gly-Asp-Asp (GAA) abolishes the RNA synthesis. To better understand the mechanism of viral RNA synthesis in CSFV, a three-dimensional model was built by homology modeling based on the alignment with several virus RdRps. The model contains 605 residues folded in the characteristic fingers, palm and thumb domains. The fingers domain contains an N-terminal region that plays an important role in conformational change. We propose that the experimentally observed promotion of polymerase efficiency by rGTP is probably due to the conformational changes of the polymerase caused by binding the rGTP. Mutation of the GDD to GAA interferes with the interaction between the residues at the polymerase active site and metal ions, and thus renders the polymerase inactive. (c) 2005 Elsevier B.V. All rights reserved.