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Zika virus (ZikV) is a flavivirus that infects neural tissues, causing congenital microcephaly. ZikV has evolved multiple mechanisms to restrict proliferation and enhance cell death, although the underlying cellular events involved remain unclear. Here we show that the ZikV-NS5 protein interacts with host proteins at the base of the primary cilia in neural progenitor cells, causing an atypical non-genetic ciliopathy and premature neuron delamination. Furthermore, in human microcephalic fetal brain tissue, ZikV-NS5 persists at the base of the motile cilia in ependymal cells, which also exhibit a severe ciliopathy. While the enzymatic activity of ZikV-NS5 appears to be dispensable, the Y25, K28 and K29 residues in the protein, that are involved in NS5-oligomerization, are essential for the localization and interaction with components of the cilium base, promoting ciliopathy and premature neurogenesis. These findings lay the foundation to develop therapies that target ZikV-NS5-multimerization, preventing the developmental malformations associated with congenital Zika syndrome

Embryonic development of the central nervous system (CNS) requires the proliferation of neural progenitor cells to be tightly regulated, allowing the formation of an organ with the right size and shape. This includes regulation of both the spatial distribution of mitosis and the mode of cell division. The centrosome, which is the main microtubule-organizing centre of animal cells, contributes to both of these processes. Here, we discuss the impact that centrosome-mediated control of cell division has on the shape of the overall growing CNS. We also review the intrinsic properties of the centrosome, both in terms of its molecular composition and its signalling capabilities, and discuss the fascinating notion that intrinsic centrosomal asymmetries in dividing neural progenitor cells are instructive for neurogenesis. Finally, we discuss the genetic links between centrosome dysfunction during development and the aetiology of microcephaly., The work in E.M.’s laboratory is supported by grants from Ministerio de Economía, Industria y Competitividad, Gobierno de España (BFU2016-77498-P and BFU2016-81887-REDT). E.G.-G. holds a Predoctoral Scholarship BES-2014-068589, J.B.-A. holds a Predoctoral Scholarship BES-2017-080050 from Ministerio de Economía, Industria y Competitividad, Gobierno de España.

The unique architecture of neurons requires the establishment and maintenance of polarity, which relies in part on microtubule-based kinesin motor transport to deliver essential cargo into axons and dendrites. In developing neurons, kinesin trafficking is essential for delivering organelles and molecules that are crucial for elongation and guidance of the growing axonal and dendritic termini. In mature neurons, kinesin cargo delivery is essential for neuron dynamic physiological functions which are critical in brain development. In this work, we followed Spatial (Tbata) gene expression during primary hippocampal neuron development and showed that it is highly expressed during dendrite formation. Spatial protein exhibits a somatodendritic distribution and we show that the kinesin motor Kif17, among other dendrite specific kinesins, is crucial for Spatial localization to dendrites of hippocampal neurons. Furthermore, Spatial down regulation in primary hippocampal cells revealed a role for Spatial in maintaining neurons' polarity by ensuring proper neurite outgrowth. This polarity is specified by intrinsic and extracellular signals that allow neurons to determine axon and dendrite fate during development. Neurotrophic factors, such as the Nerve Growth Factor (NGF), are candidate extracellular polarity-regulating cues which are proposed to accelerate neuronal polarization by enhancing dendrite growth. Here, we show that NGF treatment increases Spatial expression in hippocampal neurons. Altogether, these data suggest that Spatial, in response to NGF and through its transport by Kif17, is crucial for neuronal polarization and can be a key regulator of neurite outgrowth. © 2013., This work was supported by the Inserm, the Provence-Alpes-Côte d'Azur region and the “Association Francaise contre les Myopathies” (AFM)

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License., The different modes of stem cell division are tightly regulated to balance growth and differentiation during organ development and homeostasis, and these regulatory processes are subverted in tumor formation. Here, we developed markers that provided the single-cell resolution necessary to quantify the three modes of division taking place in the developing nervous system invivo: self-expanding, PP; self-replacing, PN; and self-consuming, NN. Using these markers and a mathematical model that predicts the dynamics of motor neuron progenitor division, we identify a role for the morphogen Sonic hedgehog in the maintenance of stem cell identity in the developing spinal cord. Moreover, our study provides insight into the process linking lineage commitment to neurogenesis with changes in cell-cycle parameters. As a result, we propose a challenging model in which the external Sonic hedgehog signal dictates stem cell identity, reflected in the consequent readjustment of cell-cycle parameters. © 2013 The Authors., The work in E.M.’s laboratory was supported by grants BFU2010-18959 and CSD2007-00008, and the work in the J.B. laboratory was supported by grants BFU2010-21847-C02-01 and 2009-SGR/01055.

Tight control of the balance between self-expanding symmetric and self-renewing asymmetric neural progenitor divisions is crucial to regulate the number of cells in the developing central nervous system. We recently demonstrated that Sonic hedgehog (Shh) signalling is required for the expansion of motor neuron progenitors by maintaining symmetric divisions. Here we show that activation of Shh/Gli signalling in dividing neuroepithelial cells controls the symmetric recruitment of PKA to the centrosomes that nucleate the mitotic spindle, maintaining symmetric proliferative divisions. Notably, Shh signalling upregulates the expression of pericentrin, which is required to dock PKA to the centrosomes, which in turn exerts a positive feedback onto Shh signalling. Thus, by controlling centrosomal protein assembly, we propose that Shh signalling overcomes the intrinsic asymmetry at the centrosome during neuroepithelial cell division, thereby promoting self-expanding symmetric divisions and the expansion of the progenitor pool., The work in E.M.’s laboratory was supported by grants BFU2013-46477-P and BFU2014-55738-REDT.

Magali Irla, Murielle Saade, Geneviève Chazal, and Catherine Nguyen contributed equally to this work; International audience; We identified the Spatial (Stromal Protein Associated with Thymii and Lymph-node) gene from an adult thymus mouse library of cDNA clones. By RT-PCR, we reported that Spatial was highly expressed in restricted areas of the central nervous system. Here, we characterize the precise cellular localization of Spatial during mouse brain development in the cerebellum, hippocampus and cortex. Five different transcript isoforms have been described for Spatial and among those, only Spatial-epsilon and -beta present a tightly controlled expression. In the cerebellum, Spatial expression is detected in the external precursor granular layer and persists as these cells migrate and differentiate to form the internal granular layer. It is also expressed in differentiating Purkinje cells with a specific somatodendritic distribution. Spatial expression in the hippocampus is spatially and temporally regulated: it is first expressed in the CA3 field, then in CA1 and later in the dentate gyrus. Interestingly, Spatial-beta expression tightly overlaps with the beginning of neuronal differentiation in both structures. Using cultured hippocampal neurons, we show that Spatial also exhibits a somatodendritic distribution and it is concentrated in some synaptic regions. Moreover, the vesicle-like cellular distribution of Spatial protein in dendrites is similar to that described for the kinesin motor protein KIF17. Immunofluorescence analyses show that Spatial colocalizes with KIF17 in dendrites of hippocampal neurons in primary culture. Additionally, coimmunoprecipitation experiments of endogenous proteins from hippocampus confirmed that Spatial and KIF17 physically interact. These findings suggest that Spatial may play a role in neuronal morphogenesis and synaptic plasticity through its interaction with the kinesin motor KIF17 in dendrites.

International audience; Viral and non-viral vectors have been developed for gene therapy, but their use is associated with unresolved problems of efficacy and safety. Efficient and safe methods of DNA delivery need to be found for medical application. Here we report a new monopolar system of non-viral electro-gene transfer into the thymus in vivo that consists of the local application of electrical pulses after the introduction of the DNA. We assessed the proof of concept of this approach by correcting ZAP-70 deficient severe combined immunodeficiency (SCID) in mice. The thymic electro-gene transfer of the pCMV-ZAP-70-IRES-EGFP vector in these mice resulted in rapid T cell differentiation in the thymus with mature lymphocytes detected by three weeks in secondary lymphoid organs. Moreover, this system resulted in the generation of long-term functional T lymphocytes. Peripheral reconstituted T cells displayed a diversified T cell receptor (TCR) repertoire, and were responsive to alloantigens in vivo. This process applied to the thymus could represent a simplified and effective alternative for gene therapy of T cell immunodeficiencies.

International audience; The Spatial gene is expressed in highly polarized cell types, such as epithelial cells in the thymus, neurons in the brain and germ cells in the testis. In this study, we report the characterization and distribution of Spatial proteins during mouse spermatogenesis. Besides Spatial-epsilon and -delta, we show that the newly described short isoform Spatial-beta is expressed specifically in round spermatids. Using indirect immunofluorescence, we detected Spatial in the cytosol of the early round spermatid. By the end stages of round spermatids, Spatial is concentrated at the opposite face of the acrosome near the nascent flagellum and in the manchette during the elongation process. Finally in mature sperm, Spatial persists in the principal piece of the tail. Moreover, we found that Spatial colocalizes with KIF17b, a testis-specific isoform of the brain kinesin-2 motor KIF17. This colocalization is restricted to the manchette and the principal piece of the sperm tail. Further, coimmunoprecipitation experiments of native proteins from testis lysates confirmed Spatial-KIF17b association through the long Spatial-epsilon isoform. Together, these findings imply a function of Spatial in spermatid differentiation as a new cargo of kinesin KIF17b, in a microtubule-dependent mechanism specific to the manchette and the principal piece of the sperm tail.

The thymus is the primary site of T cell lymphopoiesis. To undergo proper differentiation, developing T cells follow a well-ordered genetic program that strictly depends on the heterogeneous and highly specialized thymic microenvironment. In this study, we used microarray technology to extensively describe transcriptional events regulating αβ T cell fate. To get an integrated view of these processes, both whole thymi from genetically engineered mice together with purified thymocytes were analyzed. Using mice exhibiting various transcriptional perturbations and developmental blockades, we performed a transcriptional microdissection of the organ. Multiple signatures covering both cortical and medullary stroma as well as various thymocyte maturation intermediates were clearly defined. Beyond the definition of histological and functional signatures (proliferation, rearrangement), we provide the first evidence that such an approach may also highlight the complex cross-talk events that occur between maturing T cells and stroma. Our data constitute a useful integrated resource describing the main gene networks set up during thymocyte development and a first step toward a more systematic transcriptional analysis of genetically modified mice.