Histone variant innovation in a rapidly evolving chordate lineage

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A Role for Dendritic Translation of CaMKIIα mRNA in Olfactory Plasticity

Local protein synthesis in dendrites contributes to the synaptic modifications underlying learning and memory. The mRNA encoding the α subunit of the calcium/calmodulin dependent Kinase II (CaMKIIα) is dendritically localized and locally translated. A role for CaMKIIα local translation in hippocampus-dependent memory has been demonstrated in mice with disrupted CaMKIIα dendritic translation, through deletion of CaMKIIα 3′UTR. We studied the dendritic localization and local translation of CaMKIIα in the mouse olfactory bulb (OB), the first relay of the olfactory pathway, which exhibits a high level of plasticity in response to olfactory experience. CaMKIIα is expressed by granule cells (GCs) of the OB. Through in situ hybridization and synaptosome preparation, we show that CaMKIIα mRNA is transported in GC dendrites, synaptically localized and might be locally translated at GC synapses. Increases in the synaptic localization of CaMKIIα mRNA and protein in response to brief exposure to new odors demonstrate that they are activity-dependent processes. The activity-induced dendritic transport of CaMKIIα mRNA can be inhibited by an NMDA receptor antagonist and mimicked by an NMDA receptor agonist. Finally, in mice devoid of CaMKIIα 3′UTR, the dendritic localization of CaMKIIα mRNA is disrupted in the OB and olfactory associative learning is severely impaired. Our studies thus reveal a new functional modality for CaMKIIα local translation, as an essential determinant of olfactory plasticity

Embryonic cerebrospinal fluid nanovesicles carry evolutionarily conserved molecules and promote neural stem cell amplification.

During brain development, neural stem cells (NSCs) receive on-or-off signals important for regulating their amplification and reaching adequate neuron density. However, how a coordinated regulation of intracellular pathways and genetic programs is achieved has remained elusive. Here, we found that the embryonic (e) CSF contains 10¹² nanoparticles/ml (77 nm diameter), some of which were identified as exosome nanovesicles that contain evolutionarily conserved molecules important for coordinating intracellular pathways. eCSF nanovesicles collected from rodent and human embryos encapsulate protein and microRNA components of the insulin-like growth factor (IGF) signaling pathway. Supplementation of eCSF nanovesicles to a mixed culture containing eNSCs activated the IGF-mammalian target of rapamycin complex 1 (mTORC1) pathway in eNSCs and expanded the pool of proliferative eNSCs. These data show that the eCSF serves as a medium for the distribution of nanovesicles, including exosomes, and the coordinated transfer of evolutionary conserved molecules that regulate eNSC amplification during corticogenesis

Experimental characterization of the velocity field in turbulent oxy-flame of a coaxial burner

cited By 1International audienceMost industrial applications consuming a much primary energy, such fuel and gas, used different technologies of burners. The thermal efficiency and polluting emissions depends on the burner nozzle, on the fuel type and oxidant type (air or pure oxygen). This article is interested by the dynamic study in a coaxial burner consisting by two coaxial circular jets: a central jet to inject natural gas and the annular jet for pure oxygen injection. The aim of this work is the experimental study of two free coaxial jets with flame disposed in ambient air and to have the effect of varying equivalence ratio on the flow structure. This study carried in three configurations; two configurations made in lean combustion mode (Φ = 0:65, Φ = 0:8) and the stoichiometric configuration (§ = 1). The variation in the amount of oxygen in the combustion reaction affects on the longitudinal velocity, on the transversal velocity and on the turbulent fluctuation. These parameters are very important and affect directly on the flame structure. The reduction of equivalence ratio leads to increased of longitudinal and transverse velocity and promotes the fluctuation in interaction zone between natural gas and oxygen. At the stoichiometric reaction, the turbulent intensity represents a maximum in the mixing zone. This maximum increases when the height above the burner increases. © 2014 Begell House, Inc

Histone variant innovation in a rapidly evolving chordate lineage

Abstract Background Histone variants alter the composition of nucleosomes and play crucial roles in transcription, chromosome segregation, DNA repair, and sperm compaction. Modification of metazoan histone variant lineages occurs on a background of genome architecture that shows global similarities from sponges to vertebrates, but the urochordate, Oikopleura dioica, a member of the sister group to vertebrates, exhibits profound modification of this ancestral architecture. Results We show that a histone complement of 47 gene loci encodes 31 histone variants, grouped in distinct sets of developmental expression profiles throughout the life cycle. A particularly diverse array of 15 male-specific histone variants was uncovered, including a testes-specific H4t, the first metazoan H4 sequence variant reported. Universal histone variants H3.3, CenH3, and H2A.Z are present but O. dioica lacks homologs of macroH2A and H2AX. The genome encodes many H2A and H2B variants and the repertoire of H2A.Z isoforms is expanded through alternative splicing, incrementally regulating the number of acetylatable lysine residues in the functionally important N-terminal "charge patch". Mass spectrometry identified 40 acetylation, methylation and ubiquitylation posttranslational modifications (PTMs) and showed that hallmark PTMs of "active" and "repressive" chromatin were present in O. dioica. No obvious reduction in silent heterochromatic marks was observed despite high gene density in this extraordinarily compacted chordate genome. Conclusions These results show that histone gene complements and their organization differ considerably even over modest phylogenetic distances. Substantial innovation among all core and linker histone variants has evolved in concert with adaptation of specific life history traits in this rapidly evolving chordate lineage.</p

Rodent eCSF nanovesicle purification and protein expression.

<p>(<b>A</b>) Flow chart of the experimental design after CSF labeling with a tracer dye (fast green) and eCSF collection. (<b>B</b>) Histogram of size distribution of eCSF nanoparticles (per ml) determined by nanoparticle tracking analysis (NanoSight). The nanoparticles were obtained from e14 CSF from three rat litters (N = 3). The mean nanoparticle diameter was 77 nm and was obtained by Gaussian curve fitting. (<b>C</b>) Electron micrographs of rat embryonic purified nanovesicles. Scale bar: 30 nm. (<b>D</b>) Immunoblots for rat exosomal marker proteins CD63 and HSP70, and additional proteins known to be in exosomes. PTEN and PKM2. (<b>E</b>) Quantification of phosphoenol pyruvate kinase enzymatic activity determined from rat nanovesicles. (<b>F</b>) Quantification of IGF pathway-related proteins in nanovesicles isolated from e15 rat CSF using the phospho (p)-pathscan assay. Error bars: SEM. Experiments were reproduced with nanovesicles isolated from three litters (N = 3).</p

Nanovesicles from eCSF increase IGF-mTORC1 activity in eNSCs <i>in vitro</i>.

<p>(<b>A</b>) Control and nanovesicle-treated eNSCs <i>in vitro</i> immunostained for phospho-(p) S6 (red), and nestin (green), and counterstained for the nuclear marker DAPI (blue). (<b>B</b>) Zoom of the image in the white square in (A). (<b>C</b>) Number of phospho-S6-positive cells relative to total with or without nanovesicle application (N = 3 and 4 cultures, 2–4 litters for nanovesicle extraction). Experiments were reproduced in the presence of vehicle (DMSO) or 100 nM rapamycin (N = 3 each). (<b>D</b>) Relative total cell number (N = 3 each). (<b>E</b>) Percentage of nestin-positive eNSCs (N = 3 each). (<b>F</b>) Percentage of Ki67- and nestin-positive eNSCs (N = 9 control and 3 with nanovesicle). *: p<0.05, **: p<0.01, ***: p<0.001 with Student's t test or one way ANOVA. Scale bars: 200 µm (A and B). Error bars: SEM.</p

microRNA analysis of rat eCSF nanovesicles.

<p>(<b>A</b>) Heat map of microRNA microarrays from eCSF purified nanovesicles. The lighter the color (yellow) indicates higher expression whereas the darker the color (dark purple) is an indication of absence of expression. Values range from (log₂) 0.64 (bottom) to (log₂) 15.4 (top). The top 24 enriched microRNAs are listed on the right. (<b>B</b>) Rank expression of microRNAs based on microarray expression levels. (<b>C</b>) Quantitative (q) RT-PCR of exosomal RNA using selective exosomal microRNA primers or lacking primers (Neg CTL: negative control). <u>Bottom</u>: Corresponding end-point RT-PCR. (<b>D</b>) Bioinformatic analysis of microRNA interacting pathways. N = 4 litters of rats.</p