Nogo-a regulates neural precursor migration in the embryonic mouse cortex

Although Nogo-A has been intensively studied for its inhibitory effect on axonal regeneration in the adult central nervous system, little is known about its function during brain development. In the embryonic mouse cortex, Nogo-A is expressed by radial precursor/glial cells and by tangentially migrating as well as postmigratory neurons. We studied radially migrating neuroblasts in wild-type and Nogo-A knockout (KO) mouse embryos. In vitro analysis showed that Nogo-A and its receptor components NgR, Lingo-1, TROY, and p75 are expressed in cells emigrating from embryonic forebrain-derived neurospheres. Live imaging revealed an increased cell motility when Nogo-A was knocked out or blocked with antibodies. Antibodies blocking NgR or Lingo-1 showed the same motility-enhancing effect supporting a direct role of surface Nogo-A on migration. Bromodeoxyuridine (BrdU) labeling of embryonic day (E)15.5 embryos demonstrated that Nogo-A influences the radial migration of neuronal precursors. At E17.5, the normal transient accumulation of radially migrating precursors within the subventricular zone was not detectable in the Nogo-A KO mouse cortex. At E19, migration to the upper cortical layers was disturbed. These findings suggest that Nogo-A and its receptor complex play a role in the interplay of adhesive and repulsive cell interactions in radial migration during cortical developmen

Perspective: A stirring role for metabolism in cells

Based on recent findings indicating that metabolism might be governed by a limit on the rate at which cells can dissipate Gibbs energy, in this Perspective, we propose a new mechanism of how metabolic activity could globally regulate biomolecular processes in a cell. Specifically, we postulate that Gibbs energy released in metabolic reactions is used to perform work, allowing enzymes to self‐propel or to break free from supramolecular structures. This catalysis‐induced enzyme movement will result in increased intracellular motion, which in turn can compromise biomolecular functions. Once the increased intracellular motion has a detrimental effect on regulatory mechanisms, this will establish a feedback mechanism on metabolic activity, and result in the observed thermodynamic limit. While this proposed explanation for the identified upper rate limit on cellular Gibbs energy dissipation rate awaits experimental validation, it offers an intriguing perspective of how metabolic activity can globally affect biomolecular functions and will hopefully spark new research

Hypothesis-Driven, Structure-Based Design in Photopharmacology:The Case of eDHFR Inhibitors

[Image: see text] Photopharmacology uses light to regulate the biological activity of drugs. This precise control is obtained through the incorporation of molecular photoswitches into bioactive molecules. A major challenge for photopharmacology is the rational design of photoswitchable drugs that show light-induced activation. Computer-aided drug design is an attractive approach toward more effective, targeted design. Herein, we critically evaluated different structure-based approaches for photopharmacology with Escherichia coli dihydrofolate reductase (eDHFR) as a case study. Through the iterative examination of our hypotheses, we progressively tuned the design of azobenzene-based, photoswitchable eDHFR inhibitors in five design–make–switch–test–analyze cycles. Targeting a hydrophobic subpocket of the enzyme and a specific salt bridge only with the thermally metastable cis-isomer emerged as the most promising design strategy. We identified three inhibitors that could be activated upon irradiation and reached potencies in the low-nanomolar range. Above all, this systematic study provided valuable insights for future endeavors toward rational photopharmacology

Complete and incomplete spin transitions in 1D chain iron(II) compounds.

The synthesis and characterisation of two new octahedral iron(II) SCO coordination polymers [FeL1(bimm)] (1) and [FeL2(bppa)](MeOH)0.5 (2) (L1 = [3,30]-[1,2- phenylenebis-(iminomethylidyne)bis(4-phenyl-,4-butanedionato)(2-)-N,N0,O2,O20], L2 = [E,E]-[{diethyl 2,20-1,2- phenylenebis(iminomethylidyne)bis(3-oxo-3-phenylpropanato)}(2-)-N,N0,O3,O30], bimm = bis(1H-imidazol-1-yl)methane and bppa = 1,3-bis(pyridine-4-yl)propane) is presented. Results from X-ray structure analysis at different temperatures revealed in the case of 1 that the transition from a gradual to a cooperative SCO with a 5 K wide hysteresis is due to an increase of the short intermolecular contacts, which exceed a certain threshold for the cooperative effect. In the case of compound 2 an incomplete spin transition with a 4 K wide hysteresis was observed. The low temperature wMT product remains constant at a value typical for a mixed HS/LS state in stepwise spin transitions. A quantitative correlation between the cooperative effects of 12 monomer and polymer iron(II) SCO complexes and their structural properties derived from X-ray structure analysis, the so-called crystal contact index, CCI, is introduced

Martini 3 : a general purpose force field for coarse-grained molecular dynamics

The coarse-grained Martini force field is widely used in biomolecular simulations. Here we present the refined model, Martini 3 (http://cgmartini.nl), with an improved interaction balance, new bead types and expanded ability to include specific interactions representing, for example, hydrogen bonding and electronic polarizability. The updated model allows more accurate predictions of molecular packing and interactions in general, which is exemplified with a vast and diverse set of applications, ranging from oil/water partitioning and miscibility data to complex molecular systems, involving protein-protein and protein-lipid interactions and material science applications as ionic liquids and aedamers.Peer reviewe

Enhanced Functional Recovery in MRL/MpJ Mice after Spinal Cord Dorsal Hemisection

Adult MRL/MpJ mice have been shown to possess unique regeneration capabilities. They are able to heal an ear-punched hole or an injured heart with normal tissue architecture and without scar formation. Here we present functional and histological evidence for enhanced recovery following spinal cord injury (SCI) in MRL/MpJ mice. A control group (C57BL/6 mice) and MRL/MpJ mice underwent a dorsal hemisection at T9 (thoracic vertebra 9). Our data show that MRL/MpJ mice recovered motor function significantly faster and more completely. We observed enhanced regeneration of the corticospinal tract (CST). Furthermore, we observed a reduced astrocytic response and fewer micro-cavities at the injury site, which appear to create a more growth-permissive environment for the injured axons. Our data suggest that the reduced astrocytic response is in part due to a lower lesion-induced increase of cell proliferation post-SCI, and a reduced astrocytic differentiation of the proliferating cells. Interestingly, we also found an increased number of proliferating microglia, which could be involved in the MRL/MpJ spinal cord repair mechanisms. Finally, to evaluate the molecular basis of faster spinal cord repair, we examined the difference in gene expression changes in MRL/MpJ and C57BL/6 mice after SCI. Our microarray data support our histological findings and reveal a transcriptional profile associated with a more efficient spinal cord repair in MRL/MpJ mice

Enriched Monolayer Precursor Cell Cultures from Micro-Dissected Adult Mouse Dentate Gyrus Yield Functional Granule Cell-Like Neurons

BACKGROUND: Stem cell cultures are key tools of basic and applied research in Regenerative Medicine. In the adult mammalian brain, lifelong neurogenesis originating from local precursor cells occurs in the neurogenic regions of the hippocampal dentate gyrus. Despite widespread interest in adult hippocampal neurogenesis and the use of mouse models to study it, no protocol existed for adult murine long-term precursor cell cultures with hippocampus-specific differentiation potential. METHODOLOGY/PRINCIPAL FINDINGS: We describe a new strategy to obtain serum-free monolayer cultures of neural precursor cells from microdissected dentate gyrus of adult mice. Neurons generated from these adherent hippocampal precursor cell cultures expressed the characteristic markers like transcription factor Prox1 and showed the TTX-sensitive sodium currents of mature granule cells in vivo. Similar to granule cells in vivo, treatment with kainic acid or brain derived neurotrophic factor (BDNF) elicited the expression of GABAergic markers, further supporting the correspondence between the in vitro and in vivo phenotype. When plated as single cells (in individual wells) or at lowest density for two to three consecutive generations, a subset of the cells showed self-renewal and gave rise to cells with properties of neurons, astrocytes and oligodendrocytes. The precursor cell fate was sensitive to culture conditions with their phenotype highly influenced by factors within the media (sonic hedgehog, BMP, LIF) and externally applied growth factors (EGF, FGF2, BDNF, and NT3). CONCLUSIONS/SIGNIFICANCE: We report the conditions required to generate adult murine dentate gyrus precursor cell cultures and to analyze functional properties of precursor cells and their differentiated granule cell-like progeny in vitro

Constraint-induced movement therapy in the adult rat after unilateral corticospinal tract injury

Smaller spinal cord injuries often allow some degree of spontaneous behavioral improvements because of structural rearrangements within different descending fiber tracts or intraspinal circuits. In this study, we investigate whether rehabilitative training of the forelimb (forced limb use) influences behavioral recovery and plastic events after injury to a defined spinal tract, the corticospinal tract (CST). Female adult Lewis rats received a unilateral CST injury at the brainstem level. Use of the contralateral impaired forelimb was either restricted, by a cast, or forced, by casting the unimpaired forelimb immediately after injury for either 1 or 3 weeks. Forced use of the impaired forelimb was followed by full behavioral recovery on the irregular horizontal ladder, whereas animals that could not use their affected side remained impaired. BDA (biotinylated dextran amine) labeling of the intact CST showed lesion-induced growth across the midline where CST collaterals increased their innervation density and extended fibers toward the ventral and the dorsal horn in response to forced limb use. Gene chip analysis of the denervated ventral horn revealed changes in particular for growth factors, adhesion and guidance molecules, as well as components of synapse formation suggesting an important role for these factors in activity-dependent intraspinal reorganization after unilateral CST injury

Endogenous neural progenitor cells as therapeutic target after spinal cord injury

Growing knowledge about the role of neural progenitor cells supports the hope that stem cell-based therapeutic approaches aimed at restoring function in the lesioned central nervous system can be established. Possible therapies for promoting recovery after spinal cord injury include stimulating the formation of neurons and glial cells by endogenous progenitor cells. This article reviews the current knowledge about the nature of adult progenitor cells in the intact and injured spinal cord and summarizes possibilities and limitations of cellular replacement strategies based on manipulations of endogenous spinal cord progenitor cells and their environment