International audienceReversible detyrosination of α-tubulin is crucial to microtubule dynamics and functions, and defects have been implicated in cancer, brain disorganization, and cardiomyopathies. The identity of the tubulin tyrosine carboxypeptidase (TCP) responsible for detyrosination has remained unclear. We used chemical proteomics with a potent irreversible inhibitor to show that the major brain TCP is a complex of vasohibin-1 (VASH1) with the small vasohibin binding protein (SVBP). VASH1 and its homolog VASH2, when complexed with SVBP, exhibited robust and specific Tyr/Phe carboxypeptidase activity on microtubules. Knockdown of vasohibins or SVBP and/or inhibitor addition in cultured neurons reduced detyrosinated α-tubulin levels and caused severe differentiation defects. Furthermore, knockdown of vasohibins disrupted neuronal migration in developing mouse neocortex. Thus, vasohibin/SVBP complexes represent long-sought TCP enzymes

Gliomas such as oligodendrogliomas (ODG) and glioblastomas (GBM) are brain tumours with different clinical outcomes. Histology-based classification of these tumour types is often difficult. Therefore the first aim of this study was to gain microRNA data that can be used as reliable signatures of oligodendrogliomas and glioblastomas. We investigated the levels of 282 microRNAs using membrane-array hybridisation and real-time PCR in ODG, GBM and control brain tissues. In comparison to these control tissues, 26 deregulated microRNAs were identified in tumours and the tissue levels of seven microRNAs (miR-21, miR-128, miR-132, miR-134, miR-155, miR-210 and miR-409-5p) appropriately discriminated oligodendrogliomas from glioblastomas. Genomic, epigenomic and host gene expression studies were conducted to investigate the mechanisms involved in these deregulations. Another aim of this study was to better understand glioma physiopathology looking for targets of deregulated microRNAs. We discovered that some targets of these microRNAs such as STAT3, PTBP1 or SIRT1 are differentially expressed in gliomas consistent with deregulation of microRNA expression. Moreover, MDH1, the target of several deregulated microRNAs, is repressed in glioblastomas, making an intramitochondrial-NAD reduction mediated by the mitochondrial aspartate-malate shuttle unlikely. Understanding the connections between microRNAs and bioenergetic pathways in gliomas may lead to identification of novel therapeutic targets.

Synchrotron Microbeam Radiation Therapy (MRT) relies on the spatial fractionation of the synchrotron photon beam into parallel micro-beams applying several hundred of grays in their paths. Several works have reported the therapeutic interest of the radiotherapy modality at preclinical level, but biological mechanisms responsible for the described efficacy are not fully understood to date. The aim of this study was to identify the early transcriptomic responses of normal brain and glioma tissue in rats after MRT irradiation (400Gy). The transcriptomic analysis of similarly irradiated normal brain and tumor tissues was performed 6 hours after irradiation of 9 L orthotopically tumor-bearing rats. Pangenomic analysis revealed 1012 overexpressed and 497 repressed genes in the irradiated contralateral normal tissue and 344 induced and 210 repressed genes in tumor tissue. These genes were grouped in a total of 135 canonical pathways. More than half were common to both tissues with a predominance for immunity or inflammation (64 and 67% of genes for normal and tumor tissues, respectively). Several pathways involving HMGB1, toll-like receptors, C-type lectins and CD36 may serve as a link between biochemical changes triggered by irradiation and inflammation and immunological challenge. Most immune cell populations were involved: macrophages, dendritic cells, natural killer, T and B lymphocytes. Among them, our results highlighted the involvement of Th17 cell population, recently described in tumor. The immune response was regulated by a large network of mediators comprising growth factors, cytokines, lymphokines. In conclusion, early response to MRT is mainly based on inflammation and immunity which appear therefore as major contributors to MRT efficacy.

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SUMMARY:This study describes a human bone marrow endothelial cell culture in which endothelial cells are organized into capillary tubes. These endothelial cells were positive for von Willebrand Factor, expressed CD34, CD31, and L-fucose residues, took up acetylated low-density lipoproteins, contained Weibel-Palade bodies, and were ensheathed in a basal lamina (which included laminin ␤1, EDaϩ and EDbϩ fibronectin, and collagen type iv). Pericytes expressing ␣-smooth muscle (␣-SM) actin were spatially associated with the capillary tubes and there was a highly significant correlation between the number of capillary tubes and pericytes. In this model, basal angiogenesis was found to be vascular endothelial growth factor (VEGF)-dependent, because neutralization of endogenous VEGF induced a dramatic regression in the number of tubes. However, the presence of ␣-SM actin-expressing pericytes in the linings of endothelial tubes partially prevented the VEGF-neutralized tube regression. We also observed that nitric oxide production contributed to basal angiogenesis and that upregulation of nitric oxide increased the number of tubes. Tube numbers also decreased when antibodies neutralizing the integrin ␣v␤5 were applied to the cultures. Moreover, addition of any of the hematopoietic cytokines, erythropoietin, stem cell factor, granulocytic colony stimulating factor, or granulomonocytic colony stimulating factor induced a highly significant increase in tube formation. When erythropoietin and granulocytic colony stimulating factor were added, this increase was larger than the maximum increase observed with VEGF. Thus, we have described an in vitro model for human bone marrow angiogenesis in which pericytes and basal lamina matrix were associated with endothelial cells and formed fully organized capillary tubes. In this model, cytokines known to regulate hematopoiesis also seemed to be mediators of angiogenesis. This culture system may therefore prove to be a valuable tool for the study of hematopoietic cytokines on angiogenesis. (Lab Invest 2000, 80:501-511).

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