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Cortical collapse factors affect microtubule (MT) dynamics at the plasma membrane. They play important roles in neurons, as suggested by inhibition of axon growth and regeneration through the ARF activator Efa6 in C. elegans, and by neurodevelopmental disorders linked to the mammalian kinesin Kif21A. How cortical collapse factors influence axon growth is little understood. Here we studied them, focussing on the function of Drosophila Efa6 in experimentally and genetically amenable fly neurons. First, we show that Drosophila Efa6 can inhibit MTs directly without interacting molecules via an N-terminal 18 amino acid motif (MT elimination domain/MTED) that binds tubulin and inhibits microtubule growth in vitro and cells. If N-terminal MTED-containing fragments are in the cytoplasm they abolish entire microtubule networks of mouse fibroblasts and whole axons of fly neurons. Full-length Efa6 is membrane-attached, hence primarily blocks MTs in the periphery of fibroblasts, and explorative MTs that have left axonal bundles in neurons. Accordingly, loss of Efa6 causes an increase of explorative MTs: in growth cones they enhance axon growth, in axon shafts they cause excessive branching, as well as atrophy through perturbations of MT bundles. Efa6 over-expression causes the opposite phenotypes. Taken together, our work conceptually links molecular and sub-cellular functions of cortical collapse factors to axon growth regulation and reveals new roles in axon branching and in the prevention of axonal atrophy. Furthermore, the MTED delivers a promising tool that can be used to inhibit MTs in a compartmentalised fashion when fusing it to specifically localising protein domains.

Background Lack of physical activity and increased levels of stress contribute to the development of multiple physical and mental disorders. An increasing number of studies relate voluntary exercise with greater resilience to psychological stress, a process that is highly regulated by the hypothalamic-pituitary-adrenal (HPA) axis. However, the molecular mechanisms underlying the beneficial effects of exercise on stress resilience are still poorly understood. Here we have studied the impact of long term exercise and housing conditions on: a) hippocampal expression of glucocorticoid receptor ( Nr3c1 ), b) epigenetic regulation of Nr3c1 (DNA methylation at the Nr3c1-1F promoter and miR-124 expression), c) anxiety (elevated plus maze, EPM), and d) adrenal gland weight and adrenocorticotropic hormone receptor ( Mc2r ) expression. Results Exercise increased Nr3c1 and Nr3c1-1F expression and decreased miR-124 levels in the hippocampus in single-housed mice, suggesting enhanced resilience to stress. The opposite was found for pair-housed animals. Bisulfite sequencing showed virtually no DNA methylation in the Nr3c1-1F promoter region. Single-housing increased the time spent on stretch attend postures. Exercise decreased the time spent at the open arms of the EPM, however, the mobility of the exercise groups was significantly lower. Exercise had opposite effects on the adrenal gland weight of single and pair-housed mice, while it had no effect on adrenal Mc2r expression. Conclusions These results suggest that exercise exerts a positive impact on stress resilience in single-housed mice that could be mediated by decreasing miR-124 and increasing Nr3c1 expression in the hippocampus. However, pair-housing reverses these effects possibly due to stress from dominance disputes between pairs.

Our recent report that fructose supported the metabolism of some, but not all axons, in the adult mouse optic nerve prompted us to investigate in detail fructose metabolism in this tissue, a typical central white matter tract, as these data imply efficient fructose metabolism in the central nervous system (CNS). In artificial cerebrospinal fluid containing 10 mmol/L glucose or 20 mmol/L fructose, the stimulus-evoked compound action potential (CAP) recorded from the optic nerve consisted of three stable peaks. Replacing 10 mmol/L glucose with 10 mmol/L fructose, however, caused delayed loss of the 1st CAP peak (the 2nd and 3rd CAP peaks were unaffected). Glycogen-derived metabolic substrate(s) temporarily sustained the 1st CAP peak in 10 mmol/L fructose, as depletion of tissue glycogen by a prior period of aglycaemia or high-frequency CAP discharge rendered fructose incapable of supporting the 1st CAP peak. Enzyme assays showed the presence of both hexokinase and fructokinase (both of which can phosphorylate fructose) in the optic nerve. In contrast, only hexokinase was expressed in cerebral cortex. Hexokinase in optic nerve had low affinity and low capacity with fructose as substrate, whereas fructokinase displayed high affinity and high capacity for fructose. These findings suggest an explanation for the curious fact that the fast conducting axons comprising the 1st peak of the CAP are not supported in 10 mmol/L fructose medium; these axons probably do not express fructokinase, a requirement for efficient fructose metabolism.

Fully functional neural competence and integrity requires a complex array of communication means among neurons, with extracellular vesicles (EVs) emerging as a relevant mechanism for cell-cell interaction in the CNS. Despite the growing number of studies demonstrating the presence of microRNAs (miRNAs) in axon and EVs, the molecular mechanisms of those miRNAs present in EVs and their functional role in nervous system development has not been fully explored. In this study, we investigated whether neuronal EVs can have a role in neuron-to-neuron communication during the development of neuron connectivity in mouse primary cortical neuron cultures. Our results demonstrate how miR-99a can regulate axonal growth via its EV-mediated delivery and through the targeting of HS3ST2, a heparan sulphate glucosamine 3-O-sulphotransferase, which is predominantly expressed in the brain and generates rare 3-O-sulphated domains in heparan sulphate proteoglycans, with growing importance in development and neurodegenerative mechanisms. Importantly, we show how in compartmentalised microfluidic cultures, where axons are isolated from neuronal somas, the growth-promoting effects of neuron-derived EVs are local to the axon. These findings establish that neuronal EVs can deliver miRNAs to discrete subcellular domains to acutely modulate local gene expression, thereby driving axonal growth and shaping neurodevelopment.

Chronic pain arises when dorsal root ganglion (DRG) neurons become sensitised to noxious inputs, a process driven by inflammatory mediators such as prostaglandin E2 (PGE2). Local translation of axonal mRNAs is a key regulator of nociceptor plasticity, yet how axonal transcriptome dynamics contribute to inflammatory sensitisation remains unclear. Using compartmentalised culture systems and RNA-sequencing, we defined axonal and somatic transcriptomes in embryonic (E16.5) and adult (W8) DRG neurons and assessed their remodelling after PGE2 exposure. We identify a conserved core axonal transcriptome spanning embryonic to adult stages, prominently enriched for ribosomal and mitochondrial functions, consistent with sustained translational and metabolic demands. PGE2 elicited compartment-specific reprogramming: pathways related to sensory processing and pain were upregulated in axons but downregulated in somata. Functionally, prolonged axonal PGE2 exposure enhanced capsaicin-evoked Ca²⁺ responses and drove retrograde sensitisation of neuronal somata. Integrating transcriptomics with functional assays, we pinpointed Tnfrsf12a (Fn14), a cytokine receptor linked to regeneration and neuropathic pain, as a PGE2-induced axonal mRNA. Crucially, local axonal knockdown of Tnfrsf12a significantly reduced neuronal excitability, providing proof-of-concept that axonally enriched transcripts can be targeted to modulate sensitisation. These findings position conserved axonal transcriptome programmes as drivers of peripheral sensitisation and establish Tnfrsf12a as a therapeutic candidate for inflammatory pain.

Cortical collapse factors affect microtubule (MT) dynamics at the plasma membrane. They play important roles in neurons, as suggested by inhibition of axon growth and regeneration through the Arf activator Efa6 in C. elegans, and by neurodevelopmental disorders linked to the mammalian kinesin Kif21A. How cortical collapse factors influence axon growth is little understood. Here we studied them, focussing on the function of Drosophila Efa6 in experimentally and genetically amenable fly neurons. First, we show that Drosophila Efa6 can inhibit MTs directly without interacting molecules via an N-terminal 18 amino acid motif (MT elimination domain/MTED) that binds tubulin and inhibits microtubule growth in vitro and cells. If N-terminal MTED-containing fragments are in the cytoplasm they abolish entire microtubule networks of mouse fibroblasts and whole axons of fly neurons. Full-length Efa6 is membrane-attached, hence primarily blocks MTs in the periphery of fibroblasts, and explorative MTs that have left axonal bundles in neurons. Accordingly, loss of Efa6 causes an increase of explorative MTs: in growth cones, they enhance axon growth, in axon shafts, explorative MTs cause excessive branching, as well as atrophy through perturbations of MT bundles. Efa6 over-expression causes the opposite phenotypes. Taken together, our work conceptually links molecular and sub-cellular functions of cortical collapse factors to axon growth regulation and reveals new roles in axon branching and in the prevention of axonal atrophy. Furthermore, the MTED delivers a promising tool that can be used to inhibit MTs in a compartmentalised fashion when fusing it to specifically localising protein domains. Footnotes * This version contains important new experiments: (1) New in vitro data show that the MTED binds tubulin and blocks its polymerisation in the absence of other proteins; (2) live imaging and transfected fibroblasts shows that areas enriched with Efa6-FL or Efa6-Nterm::CAAX prevent MTs from elongation; (3) transfection of shot mutant neurons with Efa6-FL rescues their MT disorganisation phenotypes. * http://www.prokop.co.uk/Qu+al/RawData.zip * http://www.prokop.co.uk/Qu+al/SupplMov.html

Essential reading for anyone interested in the African continent and the diversity of human history, this Very Short Introduction looks at Africa's past and reflects on the changing ways it has been imagined and represented. Key themes in current thinking about Africa's history are illustrated with a range of fascinating historical examples, drawn from over 5 millennia across this vast continent. - ;Essential reading for anyone interested in the African continent and the diversity of human history, this Very Short Introduction looks at Africa's past and reflects on the changing ways it has been imagined and represented. Key themes in current thinking about Africa's history are illustrated with a range of fascinating historical examples, drawn from over 5 millennia across this vast continent. - ;You will finish this book better informed, with a better understanding of Africa and a clearer idea of the questions. - Robert Giddings, Tribune;This small book is a smart and stimulating essay exploring issues of history, sources and methods, Africa in the world, colonialism and postcolonialism, and the past in the present as a means of introducing students and others to academic thinking about African history. - Tom Spear, Journal of African History.

Background Osteomyelitis is a severe and often debilitating disease characterized by inflammatory destruction of bone. Despite treatment, chronic infection often develops which is associated with increased rates of treatment failure, delayed osseous-union, and extremity amputation. Within affected bone, bacteria exist as biofilms, however the impact of biofilms on osteoblasts during disease are unknown. Herein, we evaluated the effect of S . aureus biofilms on osteoblast viability, osteogenic potential, and the expression of the pro-osteoclast factor, receptor activator of NF-kB ligand (RANK-L). Methods Osteoblasts were exposed to biofilm conditioned media (BCM) from clinical wound isolates of Staphylococcus aureus under normal growth and osteogenic conditions to assess cellular viability and osteoblast differentiation, respectively. Cell viability was evaluated using a live/dead assay and by quantifying total cellular DNA at days 0, 1, 3, 5, and 7. Apoptosis following treatment with BCM was measured by flow-cytometry using the annexin V-FITC/PI apoptosis kit. Osteogenic differentiation was assessed by measuring alkaline phosphatase activity and intracellular accumulation of calcium and osteocalcin for up to 21 days following exposure to BCM. Expression of genes involved in osteogenic differentiation and osteoclast regulation, were also evaluated by quantitative real-time PCR. Results BCM from clinical strains of S . aureus reduced osteoblast viability which was accompanied by an increase in apoptosis. Osteogenic differentiation was significantly inhibited following treatment with BCM as indicated by decreased alkaline phosphatase activity, decreased intracellular accumulation of calcium and inorganic phosphate, as well as reduced expression of transcription factors and genes involved in bone mineralization in viable cells. Importantly, exposure of osteoblasts to BCM resulted in up-regulated expression of RANK-L and increase in the RANK-L/OPG ratio compared to the untreated controls. Conclusions Together these studies suggest that soluble factors produced by S . aureus biofilms may contribute to bone loss during chronic osteomyelitis simultaneously by: (1) reducing osteoblast viability and osteogenic potential thereby limiting new bone growth and (2) promoting bone resorption through increased expression of RANK-L by osteoblasts. To our knowledge these are the first studies to demonstrate the impact of staphylococcal biofilms on osteoblast function, and provide an enhanced understanding of the pathogenic role of staphylococcal biofilms during osteomyelitis.

Other effective area-based conservation measures (OECMs) have expanded area-based conservation to recognize sites that deliver effective biodiversity outcomes even if not managed for conservation. Yet our ability to identify sites likely to qualify as OECMs remains limited. To address this gap, we established and tested a set of indicators to judge whether sites meet the essential criteria to be considered OECMs, evaluating a large, global sample of 173 important conservation areas: 81 potential OECMs and 92 nearby protected areas. We found that most potential OECMs were largely in good condition with the potential to achieve conservation outcomes, but none currently met all the OECM criteria. Formally designated protected areas in our dataset performed better but the majority also failed the criteria. With so many important conservation areas unable to deliver effective conservation outcomes, our findings raise important questions about how to ensure area-based conservation promotes positive and sustained outcomes for biodiversity.Competing Interest StatementThe authors have declared no competing interest.