Examination of the stress-induced expression of the collagen binding heat shock protein, hsp47, in Xenopus laevis cultured cells and embryos

HSP47 is an endoplasmic reticulum (ER)-resident molecular chaperone involved in collagen production. This study examined the stress-induced pattern of hsp47 gene expression in Xenopus cultured cells and embryos. Sequence analysis revealed that protein encoded by the hsp47 cDNA exhibited 70-77% identity with fish, avian and mammalian HSP47. In A6 kidney epithelial cells hsp47 mRNA and HSP47 were present constitutively and inducible by heat shock but not ER stressors including tunicamycin and A23187, both of which enhanced BiP mRNA. Furthermore A23187 treatment inhibited constitutive accumulation of hsp47 mRNA and retarded heat-induced accumulation of hsp47 and hsp70 mRNA. Interestingly, hsp47 gene expression but not hsp70 or BiP mRNA accumulation was enhanced by treatment with a procollagen-specific stressor, beta-aminopropionitrile. In Xenopus embryos hsp47 mRNA was present constitutively throughout development. In tailbud embryos hsp47 mRNA was enriched in tissues associated with collagen production including notochord, somites and head region. Heat shock-induced accumulation of hsp47 mRNA was enhanced primarily in embryonic tissues already exhibiting hsp47 mRNA accumulation. These studies suggest that the pattern of Xenopus hsp47 gene expression is similar to hsp70 in response to heat shock but also displays unique features including a response to a procollagen-specific stressor and preferential expression in collagen-containing tissues.     

Chromatin signatures of pluripotent cell lines

Epigenetic genome modifications are thought to be important for specifying the lineage and developmental stage of cells within a multicellular organism. Here, we show that the epigenetic profile of pluripotent embryonic stem cells (ES) is distinct from that of embryonic carcinoma cells, haematopoietic stem cells (HSC) and their differentiated progeny. Silent, lineage-specific genes replicated earlier in pluripotent cells than in tissue-specific stem cells or differentiated cells and had unexpectedly high levels of acetylated H3K9 and methylated H3K4. Unusually, in ES cells these markers of open chromatin were also combined with H3K27 trimethylation at some non-expressed genes. Thus, pluripotency of ES cells is characterized by a specific epigenetic profile where lineage-specific genes may be accessible but, if so, carry repressive H3K27 trimethylation modifications. H3K27 methylation is functionally important for preventing expression of these genes in ES cells as premature expression occurs in embryonic ectoderm development (Eed)-deficient ES cells. Our data suggest that lineage-specific genes are primed for expression in ES cells but are held in check by opposing chromatin modifications.     

Off-axis symbiosis found: Characterization and biogeography of bacterial symbionts of Bathymodiolus mussels from Lost City hydrothermal vents

Organisms at hydrothermal vents inhabit discontinuous chemical 'islands' along mid-ocean ridges, a scenario that may promote genetic divergence among populations. The 2003 discovery of mussels at the Lost City Hydrothermal Field provided a means of evaluating factors that govern the biogeography of symbiotic bacteria in the deep sea. The unusual chemical composition of vent fluids, the remote location, and paucity of characteristic vent macrofauna at the site, raised the question of whether microbial symbioses existed at the extraordinary Lost City. If so, how did symbiotic bacteria therein relate to those hosted by invertebrates at the closest known hydrothermal vents along the Mid-Atlantic Ridge (MAR)? To answer these questions, we performed microscopic and molecular analyses on the bacteria found within the gill tissue of Bathymodiolus mussels (Mytilidae, Bathymodiolinae) that were discovered at the Lost City. Here we show that Lost City mussels harbour chemoautotrophic and methanotrophic endosymbionts simultaneously. Furthermore, populations of the chemoautotrophic symbionts from the Lost City and two sites along the MAR are genetically distinct from each other, which suggests spatial isolation of bacteria in the deep sea. These findings provide new insights into the processes that drive diversification of bacteria and evolution of symbioses at hydrothermal vents.     

Immunochemical characterization of polysaccharide antigens from six clinical strains of Enterococci

Background  

Enterococci have become major nosocomial pathogens due to their intrinsic and acquired resistance to a broad spectrum of antibiotics. Their increasing drug resistance prompts us to search for prominent antigens to develop vaccines against enterococci. Given the success of polysaccharide-based vaccines against various bacterial pathogens, we isolated and characterized the immunochemical properties of polysaccharide antigens from five strains of Enterococcus faecalis and one strain of vancomycin-resistant E. faecium.     

Evolutionary genomics in Metazoa: the mitochondrial DNA as a model system

One of the most important aspects of mitochondrial (mt) genome evolution in Metazoa is constancy of size and gene content of mtDNA, whose plasticity is maintained through a great variety of gene rearrangements probably mediated by tRNA genes. The trend of mtDNA to maintain the same genetic structure within a phylum (e.g., Chordata) is generally accepted, although more recent reports show that a considerable number of transpositions are observed also between closely related organisms. Base composition of mtDNA is extremely variable. Genome GC content is often low and, when it increases, the two complementary bases distribute asymmetrically, creating, particularly in vertebrates, a negative GC-skew. In mammals, we have found coding strand base composition and average degree of gene conservation to be related to the asymmetric replication mechanism of mtDNA. A quantitative measurement of mtDNA evolutionary rate has revealed that each of the various components has a different evolutionary rate. Non-synonymous rates are gene specific and fall in a range comparable to that of nuclear genes, whereas synonymous rates are about 22-fold higher in mt than in nuclear genes. tRNA genes are among the most conserved but, when compared to their nuclear counterparts, they evolve 100 times faster. Finally, we describe some molecular phylogenetic reconstructions which have produced unexpected outcomes, and might change our vision of the classification of living organisms.     

Transposon mutagenesis identifies cooperating genetic drivers during keratinocyte transformation and cutaneous squamous cell carcinoma progression

The systematic identification of genetic events driving cellular transformation and tumor progression in the absence of a highly recurrent oncogenic driver mutation is a challenge in cutaneous oncology. In cutaneous squamous cell carcinoma (cuSCC), the high UV-induced mutational burden poses a hurdle to achieve a complete molecular landscape of this disease. Here, we utilized the Sleeping Beauty transposon mutagenesis system to statistically define drivers of keratinocyte transformation and cuSCC progression in vivo in the absence of UV-IR, and identified both known tumor suppressor genes and novel oncogenic drivers of cuSCC. Functional analysis confirms an oncogenic role for the ZMIZ genes, and tumor suppressive roles for KMT2C, CREBBP and NCOA2, in the initiation or progression of human cuSCC. Taken together, our in vivo screen demonstrates an extremely heterogeneous genetic landscape of cuSCC initiation and progression, which can be harnessed to better understand skin oncogenic etiology and prioritize therapeutic candidates.     

Pyridazines. Part XXIX: synthesis and platelet aggregation inhibition activity of 5-substituted-6-phenyl-3(2H)-pyridazinones. Novel aspects of their biological actions

A series of 6-phenyl-3(2H)-pyridazinones with a diverse range of substituents in the 5-position have been prepared and evaluated in the search for new antiplatelet agents. A significant dependence of the substituent on the inhibitory effect has been observed. The pharmacological study of these compounds confirms that modification of the chemical group at position 5 of the 6-phenyl-3(2H)-pyridazinone system influences both variations in the antiplatelet activity and the mechanism of action.     

Permeability changes induced by polylysines in rat spermatids

High molecular weight (HMW, >15 kDa) but not low molecular weight (LMW, <15 kDa) polylysines (PLs) bound and induced permeability changes in rat spermatid plasma membranes, estimated by Mn2+ quenching of intracellular indo-1 fluorescence (K(1/2) = 3.3 +/- 0.5 microg/ml) and Co2+ quenching of intracellular calcein. The pharmacology of the Mn2+ entry pathway activated by HMW PL does not suggest that Ca2+ channels are involved in this phenomenon. Concentrations of HMW PL that induced divalent ion entry did not induce the entry of ethidium bromide, suggesting that HMW PL first bound and perturbed the plasma membrane structure inducing a non-specific increase in membrane permeability. High concentrations of HMW PL induced cell lysis (K(1/2) = 23 microg/ml). The binding of HMW PL, initially homogenous on the cell surface, subsequently progressed to a segregated pattern resembling a clustering phenomenon.