Analysis of pSC138, the multidrug resistance plasmid of Salmonella enterica serotype Choleraesuis SC-B67

Salmonella enterica serotype Choleraesuis (S. Choleraesuis) usually causes systemic infections in man and needs antimicrobial treatment. Multidrug resistance (MDR) in S. Choleraesuis is thus a great concern in the treatment of systemic non-typhoid salmonellosis. A large plasmid, pSC138, was identified in 2002 from a S. Choleraesuis strain SC-B67 that was resistant to all antimicrobial agents commonly used to treat salmonellosis, including ciprofloxacin and ceftriaxone. Complete DNA sequence of the plasmid had been determined previously (Chiu et al., 2005). In the present study, the sequence of pSC138 was reannotated in detail and compared with several newly sequenced plasmids. Some transposable elements and drug resistance genes were further delineated. Plasmid pSC138 was 138,742 bp in length and consisted of 177 open reading frames (ORFs). While 134 of the ORFs displayed significant identity levels to other plasmid and prokaryotic sequences, the remaining 43 ORFs have not been previously reported. Mobile elements, including two integrons, seven insertion sequences and eight transposons, and a truncated prophage together encompass at least 66,781 bp (48.1%) of the plasmid genome. The sequence of pSC138 consists of three major regions: a large composite transposable region Tn6088 with a Tn21-like backbone inserted by a variety of integrons or transposable elements; a transfer/maintenance region that contains a conserved ISEcp1-mediated transposon-like element Tn6092, carrying an AmpC gene, bla(CMY-2), that confers the ceftriaxone resistance; and a Rep_3 type of replication region. Another seven bacteremic strains of S. Choleraesuis that expressed the same MDR phenotype were identified during 2003-2008. The same Rep_3 type replicase and the bla(CMY-2)-containing, ISEcp1-mediated transposon-like element were found in the MDR isolates, suggesting a successful preservation and dissemination of the MDR plasmid. Comparison of pSC138 with other recently published plasmids revealed a high identity level between partial sequences of pSC138 and plasmids of the same or different incompatibility groups. The large MDR region found in pSC138 may provide a niche for the future evolution of the plasmid by acquisition of relevant resistance genes through the panoply of mobile elements and illegitimate recombination events.     

Release of erythrocytes from the spleen during exercise and splenic constriction by adrenaline infusion in the rainbow trout

Erythrocyte-supplying function of the spleen was examined in the rainbow troutSalmo gairdneri under exercise. The spleen showed remarkable reduction, about 70% in weight and about 85% in hemoglobin content, after forced exercise of 15 min. The amount of erythrocytes released from the spleen was 2.33 ml/kg body, and this amount corresponds to about 20% of the total volume of circulating erythrocytes in resting condition. No damage was observed at the spleen, splenic artery and splenic vein after the exercise. Examination of the vascular system by a corrosion casting method showed that no place other than the venous circulation exists for the erythrocytes released from the contracted spleen. The spleen was strongly constricted by infusion of adrenaline into the organ. These facts imply that the fish spleen supplies stored hemoglobin into the circulating blood in response to an increased demand of oxygen during exercise, under the control of the sympathetic nervous system.     

A toolbox for class I HDACs reveals isoform specific roles in gene regulation and protein acetylation

The class I histone deacetylases are essential regulators of cell fate decisions in health and disease. While pan- and class-specific HDAC inhibitors are available, these drugs do not allow a comprehensive understanding of individual HDAC function, or the therapeutic potential of isoform-specific targeting. To systematically compare the impact of individual catalytic functions of HDAC1, HDAC2 and HDAC3, we generated human HAP1 cell lines expressing catalytically inactive HDAC enzymes. Using this genetic toolbox we compare the effect of individual HDAC inhibition with the effects of class I specific inhibitors on cell viability, protein acetylation and gene expression. Individual inactivation of HDAC1 or HDAC2 has only mild effects on cell viability, while HDAC3 inactivation or loss results in DNA damage and apoptosis. Inactivation of HDAC1/HDAC2 led to increased acetylation of components of the COREST co-repressor complex, reduced deacetylase activity associated with this complex and derepression of neuronal genes. HDAC3 controls the acetylation of nuclear hormone receptor associated proteins and the expression of nuclear hormone receptor regulated genes. Acetylation of specific histone acetyltransferases and HDACs is sensitive to inactivation of HDAC1/HDAC2. Over a wide range of assays, we determined that in particular HDAC1 or HDAC2 catalytic inactivation mimics class I specific HDAC inhibitors. Importantly, we further demonstrate that catalytic inactivation of HDAC1 or HDAC2 sensitizes cells to specific cancer drugs. In summary, our systematic study revealed isoform-specific roles of HDAC1/2/3 catalytic functions. We suggest that targeted genetic inactivation of particular isoforms effectively mimics pharmacological HDAC inhibition allowing the identification of relevant HDACs as targets for therapeutic intervention.     

Coexistence of diploid, triploid and tetraploid crucian carp (Carassius auratus) in natural waters

Background

Crucian carp (abbreviated CC) belongs to the genus of Carassius within the family of Cyprinidae. It has been one of the most important freshwater species for Chinese aquaculture and is especially abundant in the Dongting water system of Hunan province. CC used to be considered as all diploid forms. However, coexistence of diploid (abbreviated 2nCC), triploid (abbreviated 3nCC) and tetraploid crucian carp (abbreviated 4nCC) population of the Dongting water system was first found by our recently researches.

Results

We examined the ploidy level and compared biological characteristics in different ploidy CC. In reproductive mode, 2nCC was bisexual generative and 4nCC generated all-female offspring by gynogenesis. However, 3nCC generated progenies in two different ways. 3nCC produced bisexual triploid offspring fertilized with 3nCC spermatozoa, while it produced all-female triploid offspring by gynogenesis when its ova were activated by heterogenous spermatozoa. The complete mitochondrial DNA of three different ploidy fishes was sequenced and analyzed, suggesting no significant differences. Interestingly, microchromosomes were found only in 3nCC, which were concluded to be the result of hybridization. Allogenetic DNA fragments of Sox genes were obtained in 3nCC and 4nCC, which were absent in 2nCC. Phylogenetics analysis based on Sox4 gene indicated 3nCC and 4nCC formed a separate group from 2nCC.

Conclusions

In summary, this is the first report of the co-existence of three types of different ploidy crucian carps in natural waters in China. It was proved that the coexistence of different ploidy CC was reproductively maintained. We further hypothesized that 3nCC and 4nCC were allopolyploids that resulted from hybridization. The different ploidy CC population we obtained in this study possesses great significance for the study of polyploidization and the evolution of vertebrates.     

Disruption of Ssp411 causes impaired sperm head formation and male sterility in mice

Background

We previously cloned the Ssp411 gene. We found that the Ssp411 protein is predominantly expressed in elongated spermatids in the rat testis in a stage-dependent manner. Although our findings strongly suggested that Ssp411 might play an important role in mammalian spermatogenesis, this hypothesis has not been studied.

Modification of alternative splicing in bovine somatic cell nuclear transfer embryos using engineered CRISPR-Cas13d

Animal cloning can be achieved by somatic cell nuclear transfer(SCNT), but the resulting live birth rate is relatively low. We previously improved the efficiency of bovine SCNT by exogenous melatonin treatment or by overexpression of lysine-specific demethylase 4D(KDM4D) and 4E(KDM4E). In this study, we revealed abundant alternative splicing(AS) transitions during fertilization and embryonic genome activation, and demonstrated abnormal AS in bovine SCNT embryos compared with in vitro fertilized ...