Systems biology of synaptic plasticity: a review on N-methyl-D-aspartate receptor mediated biochemical pathways and related mathematical models

Synaptic plasticity, an emergent property of synaptic networks, has shown strong correlation to one of the essential functions of the brain, memory formation. Through understanding synaptic plasticity, we hope to discover the modulators and mechanisms that trigger memory formation. In this paper, we first review the well understood modulators and mechanisms underlying N-methyl-D-aspartate receptor dependent synaptic plasticity, a major form of synaptic plasticity in hippocampus, and then comment on the key mathematical modelling approaches available in the literature to understand synaptic plasticity as the integration of the established functionalities of synaptic components.

Safety and immunogenicity of an oral DNA vaccine encoding Sip of Streptococcus agalactiae from Nile tilapia Oreochromis niloticus delivered by live attenuated Salmonella typhimurium

Attenuated Salmonella typhimurium SL7207 was used as a carrier for a reconstructed DNA vaccine against Streptococcus agalactiae. A 1.02 kb DNA fragment, encoding for a portion of the surface immunogenic protein (Sip) of S. agalactiae was inserted into pVAX1. The recombinant plasmid pVAX1-sip was transfected in EPC cells to detect the transient expression by an indirect immunofluorescence assay, together with Western blot analysis. The pVAX1-sip was transformed by electroporation into SL7207. The stability of pVAX1-sip into Salmonella was over 90% after 50 generations with antibiotic selection in vitro while remained stable over 80% during 35 generations under antibiotic-free conditions. The LD50 of SL/pVAX1-sip was 1.7 × 10(11) CFU/fish by intragastric administration which indicated a quite low virulence. Tilapias were inoculated orally at 10(8) CFU/fish, the recombinant bacteria were found present in intestinal tract, spleens and livers and eventually eliminated from the tissues 4 weeks after immunization. Fish immunized at 10(7), 10(8) and 10(9) CFU/fish with different immunization times caused various levels of serum antibody and an effective protection against lethal challenge with the wild-type strain S. agalactiae. Integration studies showed that the pVAX1-sip did not integrate with tilapia chromosomes. The DNA vaccine SL/pVAX1-sip was proved to be safe and effective in protecting tilapias against S. agalactiae infection.

First Report of Anthracnose of Alocasia macrorrhiza Caused by Colletotrichum karstii in Guangdong, China

Alocasia macrorrhiza (L.) Schott. (Araceae), native to South America, is a common, herbaceous perennial ornamental plant in tropical and subtropical areas (1). A severe leaf spot disease was observed on this plant in several places on the campus of authors' university in Guangzhou, Guangdong Province, China, in April 2013. Initial symptoms were water-soaked, dark green leaf spots. These small spots gradually expanded to 6- to 11-mm circular lesions. They were grayish-white in color with a yellow halo and many small, black, concentric dots were observed on them. Microscopic examination revealed that these small dots were acervuli, which were 100 to 300 μm in diameter, developing beneath the epidermis and becoming erumpent with age. By using routine tissue-isolation method and single-spore purification technique, four single-conidial isolates were obtained from each of four diseased leaves. These isolates formed a grayish-white colony with numerous pink spore masses on PDA at 28°C. Their mycelial radial growth rate was about 4.5 mm per day. Conidia were single-celled, hyaline, and cylindrical with an obtuse apex and protruding base; they were 12.7 to 14.2 × 4.8 to 5.9 μm in size. Conidial appressoria were irregular in shape, sepia to dark brown, solitary, and 6.9 to 8.5 × 4.6 to 5.9 μm. These morphological characteristics were consistent with the description of Colletotrichum karstii (2). The sequences of beta-tubulin gene (TUB2) and partial actin gene (ACT) of a representative isolate CAM1 were obtained by PCR amplification with primers BT2a/BT2b and ACT512F/ACT783R, respectively. These sequences were deposited in GenBank under the accession numbers of KF444947 and KF460435. BLAST searches showed a 99% homology with the TUB2 and ACT sequences of C. karstii (JX625209, KC843559). Therefore, the fungus isolated from A. macrorrhiza was identified as C. karstii by morphological and molecular characteristics. Pathogenicity tests were performed on 30-day-old plants of A. macrorrhiza grown in plastic pots (0.8 L) by spraying 15 ml conidial suspension (1 × 10⁶ conidia ml^-1) of this fungus onto each plant. The control plants were sprayed only with sterile distilled water. These plants then were placed in an intelligent artificial climate incubator with 12-h photoperiod and 100% relative humidity at 24 ± 1°C. Three replicates, each with five plants, were included in a test, and the test was repeated twice. Seven days after inoculation, the inoculated plants showed necrotic lesions on leaves similar to those observed on the campus, but no symptoms were observed on any non-inoculated controls. The same fungus C. karstii was re-isolated from the infected leaves. Although C. karstii is a well-known anthracnose pathogen on some plants belonging to family Orchidaceae (2), this is the first report of the same pathogen causing anthracnose on A. macrorrhiza in Guangdong, China. References: (1) S. Li et al. PLoS ONE 8(6):e66016, 2013. (2) Y. Yang et al. Cryptogr. Mycol. 32:229, 2011.

The delayed massive hemorrhage after gastrectomy in patients with gastric cancer: characteristics, management opinions and risk factors

AIMS

This study was designed to investigate the clinical features of delayed massive hemorrhage (DMH) after gastrectomy in patients with gastric cancer (GC).

METHODS

This study retrospectively reviewed 1536 GC patients with major gastrectomy between 1998 and 2011. Based on the time onset of postoperative bleeding, patients were divided into early postoperative hemorrhage (EPH), delayed massive hemorrhage (DMH), and no-bleeding groups. Postoperative mortality, bleeding treatment, and risk factors of hemorrhage were explored.

RESULTS

In sum, 15 (0.9%) patients suffered from DMH, with three (20%) dead cases. None of 18 (1.2%) patients with EPH died, but there were three dead cases in no-bleeding group. DMH had more extra-intestinal bleeding (P = 0.037) than EPH. Angiographic embolization was performed in 12 (80%) of DMH patients and successful in ten cases. Surgical procedures were applied in only two embolization-failed cases. Extended lymphadenectomy (P = 0.038), vascular skeletonization (P = 0.012) and advanced TNM stage (P < 0.001) were correlated with DMH.

CONCLUSIONS

DMH can be successfully managed with angiographic embolization, followed by alternative surgery. Extensive lymphadenectomy and vascular skeletonization should be discreetly performed during gastrectomy.

EGF inhibits constitutive internalization and palmitoylation-dependent degradation of membrane-spanning procancer CDCP1 promoting its availability on the cell surface

Many cancers are dependent on inappropriate activation of epidermal growth factor receptor (EGFR), and drugs targeting this receptor can improve patient survival, although benefits are generally short-lived. We reveal a novel mechanism linking EGFR and the membrane-spanning, cancer-promoting protein CDCP1 (CUB domain-containing protein 1). Under basal conditions, cell surface CDCP1 constitutively internalizes and undergoes palmitoylation-dependent degradation by a mechanism in which it is palmitoylated in at least one of its four cytoplasmic cysteines. This mechanism is functional in vivo as CDCP1 is elevated and palmitoylated in high-grade serous ovarian tumors. Interestingly, activation of the EGFR system with EGF inhibits proteasome-mediated, palmitoylation-dependent degradation of CDCP1, promoting recycling of CDCP1 to the cell surface where it is available to mediate its procancer effects. We also show that mechanisms inducing relocalization of CDCP1 to the cell surface, including disruption of its palmitoylation and EGF treatment, promote cell migration. Our data provide the first evidence that the EGFR system can function to increase the lifespan of a protein and also promote its recycling to the cell surface. This information may be useful for understanding mechanisms of resistance to EGFR therapies and assist in the design of treatments for EGFR-dependent cancers.

Val/Leu247 polymorphism of β2-glycoprotein I and thrombosis in Chinese patients with SLE

INTRODUCTION

To determine the polymorphism at position 247 of the β2-glycoprotein I (β2GPI) gene in patients with systemic lupus erythematosus (SLE) and healthy controls in the Chinese Han Population and elucidate the relationship between β2GPI polymorphisms and anti-β2GPI levels, and furthermore investigate the correlation between β2GPI polymorphisms and thrombosis in patients with SLE.

METHODS

The β2GPI polymorphisms of 300 patients with SLE and 300 healthy controls were examined by single-specific-primer polymerase chain reaction (SSP-PCR), the efficacy of which was confirmed by sequencing technology. Anti-β2GPI antibodies were tested by enzyme-linked immunosorbent assay. β2GPI polymorphisms associated with thrombosis and the presence of anti-β2GPI antibodies were also statistically evaluated with SPSS software.

RESULTS

The genotype expressions and the allele frequencies were obtained in both patients with SLE and healthy controls. The SLE patients with thrombosis had significantly higher frequencies of the VV genotype and V allele than those without thrombosis and the controls, and there were no differences in VV genotype and V allele expression between the SLE patients without thrombosis and the controls. In contrast, the presence of anti-β2GPI antibody was related to the VV genotype of β2GPI, and the anti-β2GPI-positive patients had obviously higher frequencies of the VV genotype than the negative ones and the controls.

CONCLUSION

The study results suggested that the V/V genotype and the V-encoding allele at position 247 of the β2GPI gene had strong correlation with the occurrence of thrombosis and the production of the anti-β2GPI antibodies, showing that the Val(247) β2GPI allele may be one of the genetic risk factors for the development of thrombosis in patients with SLE.

First Report of Phomopsis longicolla Causing Stem Canker of Eggplant in Guangdong, China

Eggplant (Solanum melongena L.) is an economically important vegetable crop worldwide. In August 2012, severe stem cankers were observed on eggplant at the early stage of maturation in several fields in Guangdong Province, China. Diseased plants raised cankers on the stems and branches, which resulted in wilting and stunting. No symptoms developed on eggplant fruit. Disease incidence was as high as 40% within affected fields. By using routine fungal-isolation methods and single-spore purification technique, five single-conidial isolates were obtained from each diseased stem. Colonies were grayish-white, circular, and got yellow pigmentation when placed in acidified potato dextrose agar (PDA) in an incubator at pH 4.5 and 25°C with a 12-h photoperiod. Stromata were black, large, and spreading in a concentric pattern. Conidiomata were pycnidial, and the pycnidia were round, oblate, triangular or irregular, and unilocular. Conidiophores were colorless, separated, dichotomous, and 10.0 to 18.0 × 1.5 to 2.0 μm. Alpha conidia were single-celled, ellipsoidal to fusiform, guttulate, and 6.0 to 8.0 × 2.0 to 2.5 μm. Beta conidia, produced on oat meal agar in 2 weeks at 25°C in the dark, were filiform, hamate, and 16.0 to 28.0 × 0.7 to 1.0 μm. Based on these morphological characters, the fungus was identified as Phomopsis longicolla Hobbs (1). The ITS-rDNA sequence (GenBank Accession No. KC886605) of the isolate EPPL1 of this fungus (P. longicolla EPPL1) was obtained by using universal primers ITS5/ITS4 (1). BLAST searches showed a 98% homology with the sequence of the ITS region of rDNA of P. longicolla. Phylogenetic analysis showed that P. longicolla EPPL1 clustered with P. longicolla SYJM15 and formed a distinct clade distantly related to P. vexans PV3 (GU373630), a well-known pathogen of eggplant. Digestion of PCR-amplified DNA with Alu I yielded two restriction fragments of sizes consistent with those reported for P. longicolla (2). Pathogenicity tests were performed on 30-day-old plants of cv. Yuefengzihongqie grown in a plastic pot (1 liter) in a greenhouse by using mycelial plugs and conidial suspensions of isolate EPPL1 as inocula. A mycelial plug (4 mm in diameter) from a 7-day-old PDA culture was placed on stems of both wounded and non-wounded plants and covered with sterile absorbent cotton moistened with sterile distilled water. Both wounded and non-wounded plants were inoculated with 0.5 ml of conidial suspension (1 × 10⁶ conidia ml^-1) dropped onto sterile absorbent cotton covering the stems. Control assays were performed with agar plugs and sterile distilled water only. Inoculated plants were placed in a greenhouse with a 12-h photoperiod at 28°C. Each treatment was replicated on five plants, and the test was repeated. Twenty-five days after inoculation, both wounded and non-wounded plants inoculated with either method showed raised cankers at the points of inoculation and canker lesions similar to those observed in the field expanded up and down the stems to reach lengths of 15 to 30 mm. Later, sparse, small, black pycnidia formed on the surface of the lesions. The inoculated plants exhibited stunting and premature senescence compared to controls. P. longicolla was re-isolated from the infected stems of inoculated plants. Control plants were asymptomatic. To our knowledge, this is the first report of P. longicolla causing stem canker in eggplant in Guangdong, China. Considering the economic importance of eggplant in Guangdong Province and throughout the world, further study of phomopsis stem canker of eggplant is warranted. References: (1) T. W. Hobbs et al. Mycologia 77:535, 1985. (2) A. W. Zhang et al. Plant Dis. 81:1143, 1997.

Bortezomib inhibits C2C12 growth by inducing cell cycle arrest and apoptosis

Proteosome inhibitors such as bortezomib (BTZ) have been used to treat muscle wasting in animal models. However, direct effect of BTZ on skeletal muscle cells has not been reported. In the present study, our data showed that C2C12 cells exhibited a dose-dependent decrease in cell viability in response to increasing concentrations of BTZ. Consistent with the results of cell viability, Annexin V/PI analysis showed a significant increase in apoptosis after exposing the cells to BTZ for 24h. The detection of cleaved caspase-3 further confirmed apoptosis. The apoptosis induced by BTZ was associated with reduced expression of p-ERK. Cell cycle analysis revealed that C2C12 cells underwent G2/M cell cycle arrest when incubated with BTZ for 24h. Furthermore, BTZ inhibited formation of multinucleated myotubes. The inhibition of myotube formation was accompanied by decreased expression of Myogenin. Our data suggest that BTZ induces cell death and inhibits differentiation of C2C12 cells at clinically relevant doses.

Application of two-dimensional echocardiography combined with enhanced flow in diagnosing fetal heart malformation

OBJECTIVE

The current study aims to evaluate the diagnostic accuracy of two-dimensional echocardiography combined with enhanced flow (e-flow) imaging for fetal heart malformation.

MATERIALS AND METHODS

A total of 1,639 pregnant women were enrolled. They were examined using fetal echocardiography combined e-flow. The obtained results were compared with those by postnatal examination or post-induction autopsy.

RESULTS

Complete data were obtained from 1,286 out of the 1,639 fetuses (78.46%). Two-dimensional echocardiography combined with e-flow imaging had sensitivity, specificity, a misdiagnosis rate, and a missed diagnosis rate of 98.0%, 99.3%, 2.0%, and 0.7%, respectively. It has a consistency evaluation Kappa value of 0.970 (p = 0.000).

CONCLUSION

Two-dimensional echocardiography combined with e-flow is an accurate and reliable diagnostic method for fetal heart malformation. It has high sensitivity and specificity.

Elevated plasma levels and monocyte-associated expression of CD137 ligand in patients with acute atherothrombotic stroke

BACKGROUND

CD137 ligand (CD137L) is expressed by various immune cells and exists in membrane-bound and soluble forms. Recently, CD137L was found to be localized to macrophages in human atherosclerotic lesions and CD137L levels were much higher in atherosclerotic lesions than in normal arteries. However, the role of CD137L with different forms in atherothrombotic stroke remains unclear.

PATIENTS AND METHODS

The soluble CD137L (sCD137L) protein and CD137L expression on monocytes were analyzed by an enzyme-linked immunosorbent assay and flow cytometry in peripheral blood of patients with acute ischemic atherosclerotic stroke, atherosclerosis controls and normal controls.

RESULTS

During the initial 24h after onset, the stroke patients had elevated plasma sCD137L levels (133.2 pg/ml) and CD137L expression on monocytes [7.9 ± 4.1%, 7.0 ± 4.0 mean fluorescence intensity (MFI)] as compared with normal controls (75 pg/ml, p < 0.05; 4.6 ± 2.4%, 4.1 ± 2.7 MFI, p < 0.05).

CONCLUSIONS

The dysregulation of CD137L expression may reflect a persistent chronic inflammatory response that may have been induced during early stages of the disease. Our results strongly suggest that the abnormal expression of CD137L on monocytes may lead to dyregulated CD137L/CD137 signaling and consequently form part of a positive-feedback, inflammation-promoting circuit in stroke, while the elevated sCD137L protein levels may function as a self-regulatory mechanism of CD137/CD137L interaction and costimulation.

Metabonomic analysis of Bombyx mori (Heterocera: Bombysidae) treated with acetaminophen

The feasibility of using Bombyx mori as model animal is attracting more attention. Whether the effect of drugs on the metabolite profiling was consistent with those in mammals was an aspect to evaluate the feasibility of B. mori as model animal. In this study, we used acetaminophen to treat Dazao fifth-instar B. mori, and its metabolites in hemolymph were detected by gas chromatography-mass spectrometry. The corresponding data were processed and analyzed by total model analysis, principal component analysis, partial least squares-discriminant analysis, orthogonal partial least squares-discriminant analysis, and finally, the difference metabolites between acetaminophen group and control group were selected and identified by our reference material database and the National Institute of Standard and Technology database. The results showed that acetaminophen administration induced elevation of metabolites related to energy source, the intermediate of cholesterol synthesis, and the metabolites related to melanization and also induced the decrease of metabolites in pathway of Krebs cycle, the cholesterol, and sitosterol, which suggested that acetaminophen administration inhibited energy metabolism and promoted the expenditure and imbalance of hormone and melanization.

Abstract P3-13-04: Effect of age on tolerability and efficacy of eribulin and capecitabine in patients with metastatic breast cancer treated in study 301

Background:

The Phase III trial (NCT00337103) compared eribulin (E) with capecitabine (C) in patients (pts) with metastatic breast cancer (MBC) in the 1st-, 2nd-, and 3rd-line setting. Median overall survival (OS) was 15.9 and 14.5 months (HR 0.88; 95% CI 0.77, 1.00; P = 0.056) and median progression-free survival (PFS) was 4.1 and 4.2 months (HR 1.08; 95% CI 0.93, 1.25; P = 0.30) for E and C, respectively. This analysis compares toxicity and efficacy of E and C in relation to age.

Material and methods:

In this post-hoc exploratory analysis, the effect of age on the incidence of adverse events (AEs), OS, PFS, and objective response rate (ORR) with E and C were analyzed for two age groups: ≤65 years (E, n = 468; C, n = 491) and &gt;65 years (E, n = 86; C, n = 57). For OS and PFS, analyses were stratified by HER2 and geographic region.

Results:

With increasing age, the proportion of pts with worse performance status (PS ≥1: 54.5% vs 69.2% for ≤65 and &gt;65 years, respectively), ER+ (47.4% vs 57.3%), and PgR+ MBC (41.3% vs 45.5%) increased, and the proportion with triple-negative MBC decreased (26.6% vs 20.3%). With both treatments, AEs were reported in a higher proportion of pts in the older age group, this becoming more apparent for grade 3+ AEs (E: 64.6% vs 70.2%, and C: 45.0% vs 54.4% for ≤65 and &gt;65 respectively). With E, there was a trend for increased incidence of grade 3/4 neutropenia (45.0% vs 50.0%) and leukopenia (13.7% vs 22.6%) but, in contrast, decreased peripheral sensory neuropathy (3.9% vs 1.2%) with increasing age. For C, there was a trend for increased palmar-plantar erythrodysethesia syndrome (total: 44.4% vs 50.9%; grade 3/4: 14.1% vs 17.5%), and grade 3/4 fatigue (1.8% vs 7.0%) and diarrhea (4.7% vs 10.5%) with increasing age; emesis and nausea were similar for both age groups. Dose adjustments due to AEs with E were slightly higher in the older age group: withdrawals 7.4% vs 10.7%; dose reductions 31.1% vs 36.9%; and dose delays 30.9% vs 36.9%. With C, there was a trend for an increased incidence of withdrawals (9.2% vs 21.1%) and dose delays (34.2% vs 49.1%) due to AEs with increasing age: the incidence of dose reductions was slightly higher in the older age group (31.3% vs 36.8%). In an unadjusted analysis, a trend for improved OS with E vs C was observed in both subgroups (≤65 years: median 15.8 vs 14.5 months; HR 0.90; 95% CI 0.78, 1.04; P = 0.16, and &gt;65 years: median 18.4 vs 14.1 months; HR 0.74; 95% CI 0.50, 1.12; P = 0.16). PFS and ORR for E and C were: median PFS: E, 4.0 and 5.4 months; C, 4.2 and 5.9 months; ORR: E, 10.9% and 11.6%; C, 11.6% and 10.5%, in the ≤65 and &gt;65 groups respectively.

Conclusions:

This exploratory and unadjusted analysis suggests a trend for improved OS with E in both younger and older pts with MBC. With both treatments there was a suggestion that AEs were reported in a higher proportion of pts in the older age group, this becoming more apparent for grade 3+ events. Specifically, these data suggest an increased incidence of grade 3/4 diarrhea, dose delays, and study withdrawal due to AEs in pts treated with C, and potentially suggest that with E there may be less difference between the AE profile in younger vs older pts than with C.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-13-04.

Comparative Analysis of Immune Responses in Pigs to High and Low Pathogenic Porcine Reproductive and Respiratory Syndrome Viruses Isolated in China

The CH-1a and HuN4 strains of porcine reproductive and respiratory syndrome virus (PRRSV) show different pathogenicities in pigs. To understand host immune responses against these viruses, we investigated the dynamic changes in cytokine levels produced in peripheral blood of piglets infected with the highly pathogenic PRRSV HuN4 strain or the CH-1a strain. Clinical signs, virus loads and serum cytokine levels [interferon(IFN)-α, Interleukin (IL)-1, TNF-α, IL-6, IL-12, IFN-γ, IL-10 and TGF-β] were tested. The results showed that while piglets developed effective cellular immune responses against CH-1a infection, those infected with HuN4 displayed ineffective cellular immunity, organ lesions and persistent elevated levels of immunoregulatory cytokines (IL-10 and TGF-β), which delayed the development of PRRSV-specific immune responses. These results demonstrated that HuN4 infection induced higher cytokine levels than that of CH-1a infection induced. The changes in inflammatory cytokines intensified the inflammatory reaction and damaged the tissues and organs.

Roles of brain and muscle ARNT-like 1 and Wnt antagonist Dkk1 during osteogenesis of bone marrow stromal cells

OBJECTIVES

Many studies have demonstrated that the clock gene, brain and muscle ARNT-like 1 (Bmal1), is directly related to bone ageing by affecting age-related changes to mesenchymal stem cells (MSCs). As a main developmental signal, Wnt may play an important role in this process. Here, we have aimed to elucidate whether Bmal1 positively regulates osteogenesi via Wnt pathways.

MATERIALS AND METHODS

Bone marrow stromal cells were cultured in basic and in osteo-induction medium with Wnt signalling inhibitor Dkk1 and Bmal1 transfection. Proliferation and osteogenesis of MSCs, expression of Bmal1 and activation of Wnt signalling were investigated by flow cytometry, senescence-associated β-galactosidase (SA-β-gal) staining, real-time quantitative PCR and western blot analysis.

RESULTS

Expression of Bmal1 (specially after 7 days osteo-induction), activation of Wnt signalling and osteo-related factors fell significantly during osteo-induction after Dkk1 addition. When cellular Bmal1 was increased by transfection, osteogenesis inhibition by Dkk1 was rescued to a certain extent with activation of Wnt signalling. However, Dkk1 did not significantly affect proliferation or senescence of MSCs during early periods of culture.

CONCLUSION

These findings demonstrated that Bmal1 and Wnt signalling may have a synergistic effect at a particular stage of osteogenesis. Inhibition of Wnt signalling did not greatly affect ageing of MSCs through early passages.

Histone deacetylase activity is required for embryonic posterior lateral line development

OBJECTIVES

The posterior lateral line (PLL) system in zebrafish has recently become a model for investigating tissue morphogenesis. PLL primordium periodically deposits neuromasts as it migrates along the horizontal myoseptum from head to tail of the embryonic fish, and this migration requires activity of various molecular mechanisms. Histone deacetylases (HDACs) have been implicated in numerous biological processes of development, by regulating gene transcription, but their roles in regulating PLL during embryonic development have up to now remained unexplored.

MATERIAL AND METHODS

In this study, we used HDAC inhibitors to investigate the role of HDACs in early development of the zebrafish PLL sensory system. We further investigated development of the PLL by cell-specific immunostaining and in situ hybridization.

RESULTS

Our analysis showed that HDACs were involved in zebrafish PLL development as pharmacological inhibition of HDACs resulted in its defective formation. We observed that migration of PLL primordium was altered and accompanied by disrupted development of PLL neuromasts in HDAC inhibitor-treated embryos. In these, positions of PLL neuromasts were affected. In particular, the first PLL neuromast was displaced posteriorly in a treatment dose-dependent manner. Primordium cell proliferation was reduced upon HDAC inhibition. Finally, we showed that inhibition of HDAC function reduced numbers of hair cells in PLL neuromasts of HDAC inhibitor-treated embryos.

CONCLUSION

Here, we have revealed a novel role for HDACs in orchestrating PLL morphogenesis. Our results suggest that HDAC activity is necessary for control of cell proliferation and migration of PLL primordium and hair cell differentiation during early stages of PLL development in zebrafish.

Mutations of flagellar genes fliC12, fliA and flhDC of Edwardsiella tarda attenuated bacterial motility, biofilm formation and virulence to fish

AIMS

The aim of this study was to investigate functions of flagellar genes fliC2, fliC12, fliA and flhDC in a bacterial fish pathogen Edwardsiella tarda.

METHODS AND RESULTS

In this study, functions of flagellar genes, fliC2, fliC12 (fliC1 + fliC2), fliA and flhDC (flhD + flhC) of Edw. tarda H1 were analysed by constructing in-frame deletion mutants respectively and complementary strains fliC2(+) and fliA(+) . Electron microscopy revealed that in-frame deletion of fliC12, fliA and flhDC significantly impaired the number and length of flagellar filaments, resulting in loss of both swimming and swarming motilities of the bacteria. In addition, compared to the wild-type strain and complementary strains, the flagellum-impaired mutants exhibited reduced biofilm formation ability, showed decreased ability in adherence and internalization to Epithelioma papulosum cyprini (EPC) cells and reduced pathogenicity to zebrafish.

CONCLUSIONS

These results indicated that fliC12, fliA and flhDC of Edw. tarda played essential roles in flagellar filaments structure, bacteria motility, biofilm formation, adherence, internalization and pathogenicity of this bacterium.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study revealed that flagella function in facilitating virulence and it may provide a new target for vaccines against Edw. tarda infection.