Project description:Neural precursor cells (NPCs) are multipotent cells that can generate neurons, astrocytes, and oligodendrocytes in the mammalian central nervous system. Although high mobility group nucleosomal binding domain 1 (HMGN1) was highly expressed in NPCs, its functions in neural development are not fully understood. We performed microarray analysis to examine changes in gene expression between control and HMGN1-overexpressed NPCs. NPCs derived from E11.5 mouse forebrains were infected with control or HMGN1 retrovirus in the presence of fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF). Three days after infection, the virus-infected NPCs were dissociated and seeded on poly-D-lysine -coated dishes, and subsequently the cells were cultured for 1 day without FGF2 and EGF.
Project description:During the morphogenesis of neocortex, newborn neurons undergo radial migration from the ventricular zone toward the surface of the cortical plate to form an "inside-out" lamina structure. The spatiotemporal signals that control this stereotyped radial migration remain elusive. Here, we report that a recently identified Robo family member Robo4 (Magic Roundabout), which was considered to be solely expressed in endothelial cells, is expressed in developing brain and regulates the radial migration of newborn neurons in neocortex. Downregulation of Robo4 expression in cortical newborn neurons by using in utero electroporation, with either specific siRNAs in wild-type rodents or with Cre recombinase in floxed-robo4 mutant mice, led to severe defects in the radial migration of newborn neurons with misorientation of these neurons. Moreover, newborn neurons transfected with Robo4 siRNAs exhibited significantly lower motility in a transwell migration assay (Boyden chamber) in the absence of Slit and significantly higher sensitivity to the repulsive effect of Slit in both transwell migration assay and growth cone collapse assay. Overall, our results showed an important role of Robo4 in the regulation of cortical radial migration through Slit-dependent and -independent mechanisms.
Project description:Newborn neurons maintain a very simple, bipolar shape, while they migrate from their birthplace toward their destinations in the brain, where they differentiate into mature neurons with complex dendritic morphologies. Here, we report a mechanism by which the termination of neuronal migration is maintained in the postnatal olfactory bulb (OB). During neuronal deceleration in the OB, newborn neurons transiently extend a protrusion from the proximal part of their leading process in the resting phase, which we refer to as a filopodium-like lateral protrusion (FLP). The FLP formation is induced by PlexinD1 downregulation and local Rac1 activation, which coincide with microtubule reorganization and the pausing of somal translocation. The somal translocation of resting neurons is suppressed by microtubule polymerization within the FLP The timing of neuronal migration termination, controlled by Sema3E-PlexinD1-Rac1 signaling, influences the final positioning, dendritic patterns, and functions of the neurons in the OB These results suggest that PlexinD1 signaling controls FLP formation and the termination of neuronal migration through a precise control of microtubule dynamics.
Project description:The development of neuronal networks in the neocortex depends on control mechanisms for mitosis and migration that allow newborn neurons to find their accurate position. Multiple mitogens, neurotrophic factors, guidance molecules and their corresponding receptors are involved in this process, but the mechanisms by which these signals are integrated are only poorly understood. We found that TrkB and TrkC, the receptors for brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), are activated by epidermal growth factor receptor (EGFR) signaling rather than by BDNF or NT-3 in embryonic mouse cortical precursor cells. This transactivation event regulated migration of early neuronal cells to their final position in the developing cortex. Transactivation by EGF led to membrane translocation of TrkB, promoting its signaling responsiveness. Our results provide genetic evidence that TrkB and TrkC activation in early cortical neurons do not depend on BDNF and NT-3, but instead on transactivation by EGFR signaling.
Project description:Bipolar Disorder (BD) is a complex neuropsychiatric disorder that is characterized by intermittent episodes of mania and depression and, without treatment, 15% of patients commit suicide1. Hence, among all diseases, BD has been ranked by the WHO as a top disorder of morbidity and lost productivity2. Previous neuropathological studies have revealed a series of alterations in the brains of BD patients or animal models3, such as reduced glial cell number in the patient prefrontal cortex4, up-regulated activities of the PKA/PKC pathways5-7, and changes in dopamine/5-HT/glutamate neurotransmission systems8-11. However, the roles and causation of these changes in BD are too complex to exactly determine the pathology of the disease; none of the current BD animal models can recapitulate both the manic and depressive phenotypes or spontaneous cycling of BD simultaneously12,13. Furthermore, while some patients show remarkable improvement with lithium treatment, for yet unknown reasons, other patients are refractory to lithium treatment. Therefore, developing an accurate and powerful biological model has been a challenge for research into BD. The development of induced pluripotent stem cell (iPSC) technology has provided such a new approach. Here, we developed a human BD iPSC model and investigated the cellular phenotypes of hippocampal dentate gyrus neurons derived from the patient iPSCs. Using patch clamp recording, somatic Ca2+ imaging and RNA-seq techniques, we found that the neurons derived from BD patients exhibited hyperactive action potential (AP) firing, up-regulated expression of PKA/PKC/AP and mitochondria-related genes. Moreover, lithium selectively reversed these alterations in the neurons of patients who responded to lithium treatment. Therefore, hyper-excitability is one endophenotype of BD that is probably achieved through enhancement in the PKA/PKC and Na+ channel signaling systems, and our BD iPSC model can be used to develop new therapies and drugs aimed at clinical treatment of this disease. total RNAseq from neurons generated from BD patient-specific iPS cells
Project description:During adult neurogenesis, newly formed olfactory bulb (OB) interneurons migrate radially to integrate into specific layers of the OB. Despite the importance of this process, the intracellular mechanisms that regulate radial migration remain poorly understood. Here we find that microRNA (miRNA) let-7 regulates radial migration by modulating autophagy in new-born neurons. Using Argonaute2-immunoprecipitation, we performed global profiling of miRNAs in adult-born OB neurons and identified let-7 as a highly abundant miRNA family. Knockdown of let-7 in migrating neuroblasts prevented radial migration and led to an immature morphology of newly formed interneurons. This phenotype was accompanied by a decrease in autophagic activity. Overexpression of Beclin-1 or TFEB in new-born neurons lacking let-7 resulted in re-activation of autophagy and restored radial migration. Thus, these results reveal a miRNA-dependent link between autophagy and adult neurogenesis with implications for neurodegenerative diseases where these processes are impaired.
Project description:To understand how cells communicate with each other, it is essential to define the cellular secretome, a collection of proteins including soluble secreted, unconventionally secreted and proteolytically-shed proteins. Quantitative methodologies to decipher the secretome are challenging, due to the requirement of large cell numbers and abundant serum proteins that interfere with the detection of low-abundant cellular secretome proteins. Here, we have use the highe perfomance secretome-protein-enrichment-with-click-sugars method (hiSPECS) for glyco-secretome analysis. We applied this method to investigate differences of hippocampal and cortical murine neurons. Additionally, we have inhibited the Alzheimer related protease BACE1 to identify potential substrates in the secretome of hippocampal neurons.
Project description:Despite widespread interest in using human stem cells in neurological disease modeling, a suitable model system to study human neuronal connectivity is lacking. Here, we report a protocol for efficient differentiation of hippocampal pyramidal neurons and an in vitro model for hippocampal neuronal connectivity. We developed an embryonic stem cell (ESC)- and induced pluripotent stem cell (iPSC)-based protocol to differentiate human CA3 pyramidal neurons from patterned hippocampal neural progenitor cells (NPCs). This differentiation induces a comprehensive patterning and generates multiple CA3 neuronal subtypes. The differentiated CA3 neurons are functionally active and readily form neuronal connection with dentate granule (DG) neurons in vitro, recapitulating the synaptic connectivity within the hippocampus. When we applied this neuronal co-culture approach to study connectivity in schizophrenia, we found deficits in spontaneous activity in patient iPSC derived DG–CA3 co-culture by multi-electrode array recording. In addition, both multi-electrode array recording and whole cell patch clamp electrophysiology revealed a reduction in spontaneous and evoked neuronal activity in CA3 neurons derived from schizophrenia patients. Altogether these results underscore the relevance of this new model in studying diseases with hippocampal vulnerability.
Project description:Adult neurogenesis occurs in mammals and provides a mechanism for continuous neural plasticity in the brain.However, little is known about the molecular mechanisms regulating hippocampal neural progenitor cells (NPCs) and whether their fate can be pharmacologically modulated to improve neural plasticity and regeneration. Here, we report the characterization of a unique small molecule (KHS101) that selectively induces a neuronal differentiation phenotype. Mechanism of action studies revealed a link of KHS101 to cell cycle exit and specific binding to the TACC3 protein, whose knockdown in NPCs recapitulates the KHS101-induced phenotype. Upon systemic administration, KHS101 distributed to the brainandresulted in a significant increase in neuronal differentiation in vivo. Our findings indicate that KHS101 accelerates neuronal differentiation by interaction with TACC3 and may provide a basis for pharmacological intervention.directed at endogenous NPCs. Compare expression profile of KHS101-treated hippocampal progenitor cells (2 concentrations) vs. DMSO (negative control), retinoic acid (positive control)