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Search Results: 1 - 10 of 4351 matches for " Sebastian Jessberger "
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Functional neurogenesis in the adult hippocampus: then and now
Krishna C. Vadodaria,Sebastian Jessberger
Frontiers in Neuroscience , 2014, DOI: 10.3389/fnins.2014.00055
Abstract:
Maturation and integration of adult born hippocampal neurons: signal convergence onto small Rho GTPases
Krishna C. Vadodaria,Sebastian Jessberger
Frontiers in Synaptic Neuroscience , 2013, DOI: 10.3389/fnsyn.2013.00004
Abstract: Adult neurogenesis, restricted to specific regions in the mammalian brain, represents one of the most interesting forms of plasticity in the mature nervous system. Adult-born hippocampal neurons play important roles in certain forms of learning and memory, and altered hippocampal neurogenesis has been associated with a number of neuropsychiatric diseases such as major depression and epilepsy. Newborn neurons go through distinct developmental steps, from a dividing neurogenic precursor to a synaptically integrated mature neuron. Previous studies have uncovered several molecular signaling pathways involved in distinct steps of this maturational process. In this context, the small Rho GTPases, Cdc42, Rac1, and RhoA have recently been shown to regulate the morphological and synaptic maturation of adult-born dentate granule cells in vivo. Distinct upstream regulators, including growth factors that modulate maturation and integration of newborn neurons have been shown to also recruit the small Rho GTPases. Here we review recent findings and highlight the possibility that small Rho GTPases may act as central assimilators, downstream of critical input onto adult-born hippocampal neurons contributing to their maturation and integration into the existing dentate gyrus (DG) circuitry.
Adult Hippocampal Neurogenesis and Plasticity in the Infrapyramidal Bundle of the Mossy Fiber Projection: I. Co-Regulation by Activity
Benedikt R?mer,Julia Krebs,Rupert W. Overall,Klaus Fabel,Harish Babu,Linda Overstreet-Wadiche,Sebastian Jessberger,Gerd Kempermann
Frontiers in Neuroscience , 2011, DOI: 10.3389/fnins.2011.00107
Abstract: Besides the massive plasticity at the level of synapses, we find in the hippocampus of adult mice and rats two systems with very strong macroscopic structural plasticity: adult neurogenesis, that is the lifelong generation of new granule cells, and dynamic changes in the mossy fibers linking the dentate gyrus to area CA3. In particular the anatomy of the infrapyramidal mossy fiber tract (IMF) changes in response to a variety of extrinsic and intrinsic stimuli. Because mossy fibers are the axons of granule cells, the question arises whether these two types of plasticity are linked. Using immunohistochemistry for markers associated with axonal growth and pro-opiomelanocortin (POMC)–GFP mice to visualize the post-mitotic maturation phase of adult hippocampal neurogenesis, we found that newly generated mossy fibers preferentially but not exclusively contribute to the IMF. The neurogenic stimulus of an enriched environment increased the volume of the IMF. In addition, the IMF grew with a time course consistent with axonal outgrowth from the newborn neurons after the induction of neurogenic seizures using kainate. These results indicate that two aspects of plasticity in the adult hippocampus, mossy fiber size and neurogenesis, are related and may share underlying mechanisms. In a second part of this study, published separately (Krebs et al., 2011) we have addressed the question of whether there is a shared genetics underlying both traits.
Adult Hippocampal Neurogenesis and Plasticity in the Infrapyramidal Bundle of the Mossy Fiber Projection: II. Genetic Covariation and Identification of Nos1 as Linking Candidate Gene
Julia Krebs,Benedikt R?mer,Rupert W. Overall,Klaus Fabel,Harish Babu,Robert W. Williams,Sebastian Jessberger,Gerd Kempermann
Frontiers in Neuroscience , 2011, DOI: 10.3389/fnins.2011.00106
Abstract: The hippocampus of adult rodents harbors two systems exhibiting structural plasticity beyond the level of synapses and dendrites. First, the persistent generation of granule cells (adult neurogenesis); second, dynamic changes in the mossy fibers (MF), in particular in the infrapyramidal mossy fiber (IMF) tract. Because MFs are the axons of granule cells, the question arises whether these two types of plasticity are linked. In the first part of this study (R?mer et al., 2011) we have asked how both traits are regulated in relation to each other. In the present part, we asked whether, besides activity-dependent co-regulation, there would also be signs of genetic co-regulation and co-variance. For this purpose we used the BXD panel of recombinant inbred strains of mice, a unique genetic reference population that allows genetic association studies. In 31 BXD strains we did not find correlations between the traits describing the volume of the MF subfields and measures of adult neurogenesis. When we carried out quantitative trait locus mapping for these traits, we found that the map for IMF volume showed little overlap with the maps for the other parts of the projection or for adult neurogenesis, suggesting that to a large degree the IMF is regulated independently. The highest overlapping peak in the genome-wide association maps for IMF volume and the number of new neurons was on distal chromosome 5 (118.3–199.2 Mb) with an LRS score of 5.5 for IMF and 6.0 for new neurons. Within this interval we identified Nos1 (neuronal nitric oxide synthase) as a cis-acting (i.e., presumably autoregulatory) candidate gene. The expression of Nos1 is has been previously linked with both IMF and adult neurogenesis, supporting our findings. Despite explaining on its own very little of the variance in the highly multigenic traits studied, our results suggest Nos1 may play a part in the complex genetic control of adult neurogenesis and IMF morphology.
Cdk5 Regulates Accurate Maturation of Newborn Granule Cells in the Adult Hippocampus
Sebastian Jessberger,Stefan Aigner,Gregory D. Clemenson Jr.,Nicolas Toni,D. Chichung Lie,?zlem Karalay,Rupert Overall,Gerd Kempermann,Fred H. Gage
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0060272
Abstract: Newborn granule cells become functionally integrated into the synaptic circuitry of the adult dentate gyrus after a morphological and electrophysiological maturation process. The molecular mechanisms by which immature neurons and the neurites extending from them find their appropriate position and target area remain largely unknown. Here we show that single-cell–specific knockdown of cyclin-dependent kinase 5 (cdk5) activity in newborn cells using a retrovirus-based strategy leads to aberrant growth of dendritic processes, which is associated with an altered migration pattern of newborn cells. Even though spine formation and maturation are reduced in cdk5-deficient cells, aberrant dendrites form ectopic synapses onto hilar neurons. These observations identify cdk5 to be critically involved in the maturation and dendrite extension of newborn neurons in the course of adult neurogenesis. The data presented here also suggest a mechanistic dissociation between accurate dendritic targeting and subsequent synapse formation.
Variability of doublecortin-associated dendrite maturation in adult hippocampal neurogenesis is independent of the regulation of precursor cell proliferation
Tobias Plümpe, Dan Ehninger, Barbara Steiner, Friederike Klempin, Sebastian Jessberger, Moritz Brandt, Benedikt R?mer, Gerardo Rodriguez, Golo Kronenberg, Gerd Kempermann
BMC Neuroscience , 2006, DOI: 10.1186/1471-2202-7-77
Abstract: We found that (1) 20% of the DCX population were precursor cells in cell cycle, whereas more than 70% were postmitotic, (2) the time span until newborn cells had reached the most mature stage associated with DCX expression varied between 3 days and several weeks, (3) positive or negative regulation of precursor cell proliferation did not alter the pattern and dynamics of dendrite development. Dendrite maturation was largely independent of close contacts to astrocytes.These data imply that dendrite maturation of immature neurons is initiated at varying times after cell cycle exit, is variable in duration, and is controlled independently of the regulation of precursor cell proliferation. We conclude that in addition to the major regulatory events in cell proliferation and selective survival, additional micro-regulatory events influence the course of adult hippocampal neurogenesis.Neuronal development in the adult hippocampus proceeds from the division of a precursor cell to a mature new granule cell [1,2]. A large surplus of neurons is generated, from which only a subset is recruited for survival and long-term integration into the network. This process is activity-dependently regulated. Once cells have been selected they have a lasting existence [3]. Adult hippocampal neurogenesis appears to originate from an astrocyte-like precursor cell (type-1 cell/vertical astrocyte) that gives rise to a transiently amplifying progenitor cell (type-2 cell) [4,5]. At this stage first indications of neuronal determination are found. The cells receive, for example, their first synaptic input, which is GABAergic [6,7]. The newly generated cells also begin to express doublecortin (DCX) [8-12].DCX is a protein associated with neuronal differentiation that functionally has been linked to cell migration and possible other aspects of maturation, including synaptogenesis [13]. Mutations of the DCX gene cause migration disorders such as cortical laminar heterotopia and the doublecortex syndr
Cdk5 Regulates Accurate Maturation of Newborn Granule Cells in the Adult Hippocampus
Sebastian Jessberger ,Stefan Aigner,Gregory D Clemenson Jr.,Nicolas Toni,D. Chichung Lie,?zlem Karalay,Rupert Overall,Gerd Kempermann,Fred H Gage
PLOS Biology , 2008, DOI: 10.1371/journal.pbio.0060272
Abstract: Newborn granule cells become functionally integrated into the synaptic circuitry of the adult dentate gyrus after a morphological and electrophysiological maturation process. The molecular mechanisms by which immature neurons and the neurites extending from them find their appropriate position and target area remain largely unknown. Here we show that single-cell–specific knockdown of cyclin-dependent kinase 5 (cdk5) activity in newborn cells using a retrovirus-based strategy leads to aberrant growth of dendritic processes, which is associated with an altered migration pattern of newborn cells. Even though spine formation and maturation are reduced in cdk5-deficient cells, aberrant dendrites form ectopic synapses onto hilar neurons. These observations identify cdk5 to be critically involved in the maturation and dendrite extension of newborn neurons in the course of adult neurogenesis. The data presented here also suggest a mechanistic dissociation between accurate dendritic targeting and subsequent synapse formation.
Dendritic Cell Podosome Dynamics Does Not Depend on the F-actin Regulator SWAP-70
Anne G?tz, Rolf Jessberger
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0060642
Abstract: In addition to classical adhesion structures like filopodia or focal adhesions, dendritic cells similar to macrophages and osteoclasts assemble highly dynamic F-actin structures called podosomes. They are involved in cellular processes such as extracellular matrix degradation, bone resorption by osteoclasts, and trans-cellular diapedesis of lymphocytes. Besides adhesion and migration, podosomes enable dendritic cells to degrade connective tissue by matrix metalloproteinases. SWAP-70 interacts with RhoGTPases and F-actin and regulates migration of dendritic cells. SWAP-70 deficient osteoclasts are impaired in F-actin-ring formation and bone resorption. In the present study, we demonstrate that SWAP-70 is not required for podosome formation and F-actin turnover in dendritic cells. Furthermore, we found that toll-like receptor 4 ligand induced podosome disassembly and podosome-mediated matrix degradation is not affected by SWAP-70 in dendritic cells. Thus, podosome formation and function in dendritic cells is independent of SWAP-70.
Cohesin in Oocytes—Tough Enough for Mammalian Meiosis?
Ekaterina Revenkova,Caroline Adelfalk,Rolf Jessberger
Genes , 2010, DOI: 10.3390/genes1030495
Abstract: Sister chromatid cohesion is essential for cell division. During meiosis, it is also required for proper synapsis of pairs of sister chromatids and for chiasma formation and maintenance. Since mammalian oocytes remain arrested in late prophase for a very long period—up to five decades in humans—the preservation of cohesion throughout this period is a formidable challenge. Mouse models with cohesin deficiencies and aging wild-type mice showed that this challenge is not fully met: cohesion weakens and deteriorates with increasing age. These recent findings have highly significant implications for our comprehension of the genesis of aneuploidies.
Time-Dependent Ferrofluid Dynamics in Symmetry Breaking Transverse  [PDF]
Sebastian Altmeyer
Open Journal of Fluid Dynamics (OJFD) , 2013, DOI: 10.4236/ojfd.2013.32015
Abstract: We investigate the Taylor-Couette flow of a rotating ferrofluid under the influence of symmetry breaking transverse magnetic field in counter-rotating small-aspect-ratio setup. We find only changing the magnetic field strength can drive the dynamics from time-periodic limit-cycle solution to time-independent steady fixed-point solution and vice versa. Thereby both solutions exist in symmetry related offering mode-two symmetry with left-or right-winding characteristics due to finite transverse magnetic field. Furthermore the time-periodic limit-cycle solutions offer alternately stroboscoping both helical left-and right-winding contributions of mode-two symmetry. The Navier-Stokes equations are solved with a second order time splitting method combined with spatial discretization of hybrid finite difference and Galerkin method.
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