Neuron Regeneration Symposium 10.27-28.2014! Speaker Abstracts The University of Texas at San Antonio Presented in schedule order. I. Genes Expressed by Human Cortical Radial Glia Help Explain Developmental and Evolutionary Cortical Expansion Recent insights from studies of the developing cerebral cortex highlight potential evolutionary changes that may contribute to structural and functional features of the human brain. Radial glial cells (RG) undergo symmetric divisions to self-renew and asymmetric divisions to generate neuronal precursors that can further proliferate in the subventricular zone (SVZ) to increase neuronal number. The developing human cortex contains a massively expanded SVZ, not present in rodent that is thought to account for the bulk of cortical neurogenesis. Evolutionary expansion of the neocortex is partially attributed to an abundance of radial glia-like cells (oRGs) within this zone. We found that oRG cells uniquely display mitotic somal translocation (MST) where the soma rapidly translocates towards the cortical plate prior to cytokinesis. The molecular motors driving MST include activation of the Rho effector ROCK and non-muscle myosin II, but not microtubule polymerization or centrosomal guidance. Many neurodevelopmental disease genes target the Rho-ROCK-myosin pathway and are expressed by oRGs, suggesting possible involvement in pathophysiology. We have begun to characterize gene expression patterns and gene regulatory networks of human RG cells using two complementary approaches to disentangle cell-type and cell-state specific gene expression patterns from heterogeneous tissue. First, we developed a strategy that exploits variation in cellular abundance across serial sections to reveal cell type-specific patterns of gene expression. Second, we directly sequenced mRNA from single cells for unbiased classification of cell identity and for detection of candidate effector genes of activated pathways. Interestingly, the transcriptional profiles of human and mouse RG diverged for specific signaling pathways. Arnold R. Kriegstein MD PhD John G. Bowes Distinguished Professor in Stem Cell and Tissue Biology Director, The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research at UCSF UCSF School of Medicine II. Adhesive and Cytoskeletal Control of Dendrite Development and Stability Proper brain function relies on the extensive synaptic connections that form between neurons. Most excitatory synapses form on small actin-rich protrusions from the sides of dendrites called dendritic spines. Neurons normally have highly-branched dendrites studded with many spines that receive inputs from other neurons. Defects in dendritic spine and dendrite arbor development and stabilization contribute to the pathology of mental retardation, autism, and psychiatric and neurodegenerative diseases. Despite the importance of maintaining neuronal connectivity, the mechanisms that underlie long-term dendritic spine and dendrite stability are poorly understood. Our laboratory has discovered that integrin α3β1 adhesion receptor signaling through Abl2/Arg tyrosine kinase and a set of key downstream targets confers long-term dendritic spine and dendrite arbor stability in the adolescent mouse forebrain. When key upstream components in this pathway (e.g. integrins α3 and β1, Arg) are inactivated, brains mature normally through late adolescence, but exhibit a 25-30% loss of dendritic spines and dendrite arbors by young adulthood, accompanied by deficits in learning, memory, and behavioral flexibility. Importantly, mutations or deletions affecting several pathway components (Arg, p190RhoGAP, SHP-2, integrin β1, GluN2B) are associated with neurodevelopmental and psychiatric disorders in humans. These findings underscore the importance of the mechanisms we have elucidated for human brain circuit stability and function. I will discuss our latest efforts to identify the upstream regulators and downstream targets of this key signaling module and their impact on dendrite and dendritic spine development and stability. Anthony J. Koleske, PhD Professor Yale University Dept. of Molecular Biophysics and Biochemistry Dept. of Neurobiology Interdepartmental Neuroscience Program Presented by The UTSA Neurosciences Institute & The Cell & Molecular Biology Program Neuron Regeneration Symposium 10.27-28.2014! Speaker Abstracts The University of Texas at San Antonio III. Playing in Traffic: Neuronal Endosomes at the Crossroads during Development and Beyond Neuronal endosomes are essential for membrane receptor trafficking to and within dendrites and axons. In addition, endosomes participate in a variety of signaling events, as well as regulating the rates of recycling and degradation. Endosomal trafficking is thus at the center of receptor trafficking in neurons and participates in various neuronal functions, such as synaptic plasticity and axon outgrowth. Endosomal trafficking also plays crucial but poorly understood roles during neurogenesis and early migration of newborns in the cortex. In addition, dysfunctions of the endolysosomal system have been implicated in a number of neurodegenerative conditions. However, due to the unique functions and morphologies of neurons, the neuronal endosomal system differs from the canonical endosomal system found in fibroblasts. Intriguingly, neurons express cell-type specific proteins that localize to endosomes, but little is known about how these neuronal proteins interface with canonical endosomes and ubiquitously expressed endosomal components. NEEP21 (Neuron-Enriched Endosomal Protein 21kd) localizes to somatodendritic endosomes, and downregulation of NEEP21 perturbs the correct trafficking of multiple receptors, including glutamate receptors (GluA2) during LTP and amyloidogenic processing of bAPP. Our own work implicated NEEP21 in correct trafficking of the axonal cell adhesion molecule L1/NgCAM. Here we characterize NEEP21-containing compartments and their dynamic relationship with ubiquitous endosomal regulators in order to begin to understand neuronal adaptation to endosomal trafficking. Bettina Winckler, PhD Professor of Neuroscience University of Virginia 409 Lane Road, MR4- 6116 Charlottesville, VA 22908 IV. The Yin and Yang of Adult Hippocampal Neurogenesis Adult hippocampal neurogenesis occurs in a wide variety of mammalian species, including non-human primates and humans. After most physiological stimuli, adult hippocampal neurogenesis appears to be beneficial for learning and memory and mood regulation. Our laboratory has used mouse genetic models and stem cell culture approaches to define the transcriptional and epigenetic circuitry controlling neural stem cell fate. We have systematically dissected the function and mechanisms of individual transcriptional factors and histone modifying enzymes that function in the stepwise progression of quiescent neural stem cells to mature dentate granule neurons in the adult mammalian brain. In spite of the potential of adult hippocampal neurogenesis in regenerative medicine and science, there may be a dark side of adult neurogenesis. Epileptic activity leads to aberrant hippocampal neurogenesis, including increased proliferation of neural progenitors, production of ectopic granule cells (EGCs), mossy fiber sprouting and persistence of hilar basal dendrites on adult-born granule. Collectively, aberrant new neurons may disrupt neural circuits and contribute to chronic epilepsy and cognitive impairment. In my lecture, I will present two stories highlighting the yin and yang of adult hippocampal neurogenesis. Our results provide mechanistic insight for strategies to promote the adult neural stem cell pool towards preventing age-related cognitive decline and also provide a cautionary note regarding potential neuroregenerative strategies. Supported by NIH grants R01AG032383 and K02AG041815 and Welch Foundation I-1660. Jenny Hsieh, PhD Associate Professor Department of Molecular Biology UT Southwestern Medical Center, Dallas, Texas USA Presented by The UTSA Neurosciences Institute & The Cell & Molecular Biology Program Neuron Regeneration Symposium 10.27-28.2014! Speaker Abstracts The University of Texas at San Antonio V. Epigenetic Regulations Underlying Cell Fate Transition in Adult Neurogenic Niches Adult Neurogenesis continues life-long in two restricted brain regions including the subventricular zone (SVZ) on the walls of the lateral ventricles and the subgranular zone (SGZ) within the dentate gyrus of hippocampus. While the phenomenon of adult neurogenesis raises fundamental questions regarding the regulation of cell fate transition, the mis-regulation of cell fate is critical to prime diseases, such as cancer. Our research focus is to integrate genetic and epigenetic information to delineate the mechanisms underlying cell fate transition and diseases initiation/progression using both rodent and primate models. Our preliminary study suggest that cell fate determination in these neurogenic niches is in part maintained and regulated through epigenetic mechanisms including histone modifications, which have emerged as one of influential players on gene expression signature. The molecular events with focus on histone methylation that regulate self-renewal and lineage commitment in adult neurogenic niches will be the main topic of this presentation. Chin-Hsing Annie Lin, PhD Assistant professor University of Texas at San Antonio Department of Biology UTSA Neuroscience Institute San Antonio Cellular Therapeutics Institute VI. MicroRNA Regulation of Neural Precursor Maintenance and Specification During development neural precursors first divide symmetrically to produce new precursors, thereby expanding the precursor population. Subsequently, neural precursors begin to divide asymmetrically, generating first neurons and later glia while at the same time maintaining new precursor production. Near the end of development most precursors stop dividing and terminally differentiate. Changes in the balance of symmetric proliferative divisions, asymmetric self-renewing divisions and terminal divisions have important consequences for brain size and developmental disorders. Vertebrate neural precursor cells have apicobasal polarity and how this polarity is modulated influences whether precursors undergo symmetric or asymmetric divisions. For example, precursors that maintain high levels of Par proteins associated with apical membrane persist in a self-renewing state whereas loss of apical Par proteins correlates with differentiation. Distribution of apical Par proteins during symmetric proliferative and asymmetric divisions has been extensively investigated but the mechanisms that downregulate Par proteins to promote terminal differentiation are not known. Using zebrafish as a model system, we found that microRNA miR-219 negatively regulates pard3 and prkci mRNAs, which encode apical Par proteins, via single target sites within their 3ʼ UTRs. Blocking the ability of miR-219 to bind these target sites prevented downregulation of apical proteins in the developing spinal cord, maintained precursors in a proliferative state and interfered with production of late-born neurons and glia. Notably, loss of miR-219 function and maintenance of apical Par proteins increases the duration and level of Sonic Hedgehog signaling in the spinal cord. Therefore, modulation of apical Par protein levels by miR-219 may tune the responsiveness of neural precursors to Sonic Hedgehog, determining whether they proliferate or differentiate. Bruce Appel, PhD Professor of Pediatrics Diane G. Wallach Endowed Chair of Pediatric Stem Cell Biology Director, Graduate Program in Cell Biology, Stem Cells and Development Director, Pediatric Stem Cell Biology Program University of Colorado School of Medicine and Children's Hospital Colorado Presented by The UTSA Neurosciences Institute & The Cell & Molecular Biology Program Neuron Regeneration Symposium 10.27-28.2014! Speaker Abstracts The University of Texas at San Antonio VII. Myelin Plasticity after Spinal Cord Injury: New Targets to Improve Axonal Conduction & Function Myelin regeneration has thought to be limited after trauma to the central nervous system. In addition, new myelin has been proposed to be abnormally thin and likely unable to significantly contribute to recovery. Recently it has been shown that the central nervous system has endogenous stem cells that generate many new glia after spinal cord injury. In turn, novel myelin reporter systems demonstrate that endogenous stem cells contribute to a remarkable level of myelin regeneration that likely contributes to the functional recovery of spared axons. Strikingly, most abnormal myelin appears to be derived from degenerating cells rather than regenerating myelin. In the future, therapeutic regulation of myelin parameters such as internodal length and thickness as well as clearance of degenerating myelin likely holds great promise for optimizing axonal sparing and nerve function. Philip J. Horner, PhD Professor, Neurological Surgery Institute for Stem Cell and Regenerative Medicine University of Washington VIII. Functional Genomics and Spinal Cord Injury Development and regeneration of the nervous system requires the regulated formation of axons and dendrites. A comprehensive understanding of neuronal process development on a molecular level is lacking. Phenotypic analysis of primary neurons offers a powerful way to study how different genes influence neuronal differentiation. We have performed various screens to identify genes and compounds that enhance axon growth. The first campaign tested over 600 developmentally regulated genes in cortical neurons and identified KLF transcription factors as potent intrinsic regulators of axon growth. A second screening campaign started by looking at the effect of kinase and phosphatase overexpression on developing neurons in culture. Over 300 kinases and 124 esterases and phosphatases were tested in hippocampal neurons. A subsequent screen of over 1600 kinase inhibitors allowed us to identify kinases to be inhibited and others to be avoided when trying to promote axon growth. A third screening campaign of genes, including miRNAs, expressed in regenerating dorsal root ganglion neurons uncovered transcription factors and miRNAs that can enhance growth of CNS neurons. This campaign was based on two RNA-seq projects. These projects will be discussed, along with strategies using light sheet fluorescent microscopy to speed in vivo testing. Vance Lemmon, PhD Walter G. Ross Distinguished Chair in Developmental Neuroscience Professor of Neurological Surgery The Miami Project to Cure Paralysis Program Director in Computational Biology Center for Computational Sciences Univ. of Miami Miller School of Medicine Presented by The UTSA Neurosciences Institute & The Cell & Molecular Biology Program