The L1 Cell Adhesion Molecule Is Essential for Topographic Mapping of Retinal Axons

The retinocollicular projection is a preferred axon guidance pathway for investigating molecular mechanisms of synaptic targeting in the mammalian CNS. Here we identify a previously unrecognized role of the L1 cell adhesion molecule in topographic mapping of retinal ganglion cell (RGC) axons to their targets in the mouse superior colliculus (SC). L1 was transiently expressed on RGC axons during axon growth and targeting. DiI labeling of retinal axons revealed that temporal axons of L1-minus mice bypassed correct target locations in the anterior SC, forming termination zones at incorrect posterior sites, which were often skewed along the mediolateral axis. During development of the retinotopic map L1-minus temporal axons extended across the anteroposterior axis of the SC like wild-type axons but failed to arborize at normal anterior target sites. L1-minus RGC axons exhibited normal crossing at the optic chiasm and fasciculation of the optic nerve. Results suggest that retinal axons require the function of L1 in addition to repellent EphA guidance receptors to achieve proper topographic mapping

GCIRS16SW: a massive eclipsing binary in the Galactic Center

We report on the spectroscopic monitoring of GCIRS16SW, an Ofpe/WN9 star and LBV candidate in the central parsec of the Galaxy. SINFONI observations show strong daily spectroscopic changes in the K band. Radial velocities are derived from the HeI 2.112 um line complex and vary regularly with a period of 19.45 days, indicating that the star is most likely an eclipsing binary. Under various assumptions, we are able to derive a mass of ~ 50 Msun for each component.Comment: 4 pages, 4 figures, ApJ Letters accepte

Abnormalities in Neuronal Process Extension, Hippocampal Development, and the Ventricular System of L1 Knockout Mice

In humans, mutations in the L1 cell adhesion molecule are associated with a neurological syndrome termed CRASH, which includes corpus callosum agenesis, mental retardation, adducted thumbs, spasticity, and hydrocephalus. A mouse model with a null mutation in the L1 gene

CHL1 cooperates with PAK1–3 to regulate morphological differentiation of embryonic cortical neurons

The cell adhesion molecule Close Homologue of L1 (CHL1) is important for apical dendritic projection and laminar positioning of pyramidal neurons in caudal regions of the cerebral cortex. The p21-activated kinase (PAK 1-3) subfamily of serine/threonine kinases has also been implicated in regulating cell adhesion, migration, and morphology. Immunofluorescence staining in mouse embryonic brain showed that PAK1-3 was expressed in embryonic cortex and colocalized with CHL1 during neuronal migration and differentiation. To investigate a cooperative function for CHL1 and PAK in pyramidal cell differentiation or migration, a dominant-negative PAK mutant (PAK1 AID) that inhibits PAK1-3 kinase activity while coexpressing a green fluorescent protein (GFP) reporter was electroporated into the lateral ventricles of wild type and CHL1 null mutant mouse embryos (E14.5), then brain slices were cultured and neurons analyzed for laminar positioning and morphology by confocal microscopy after 3 days in vitro. Expression of PAK1 AID in CHL1 mutant cortex inactivated PAK and caused embryonic cortical neurons to branch profusely in the intermediate zone and cortical plate. The number of nodes, terminals and length of leading processes/apical dendrites of CHL1 mutant embryos expressing PAK1 AID increased dramatically, compared to CHL1 mutants without PAK1 AID, or wild type embryos with or without PAK1 AID. These findings suggest that CHL1 and PAK1-3 kinase cooperate, most likely in independent pathways, in regulating morphological development of the leading process/apical dendrite of embryonic cortical neurons

On how the optical depth tunes the effects of ISM neutral atom flow on debris disks

The flux of ISM neutral atoms surrounding stars and their environment affects the motion of dust particles in debris disks, causing a significant dynamical evolution. Large values of eccentricity and inclination can be excited and strong correlations settle in among the orbital angles. This dynamical behaviour, in particular for bound dust grains, can potentially cause significant asymmetries in dusty disks around solar type stars which might be detected by observations. However, the amount of orbital changes due to this non--gravitational perturbation is strongly limited by the collisional lifetime of dust particles. We show that for large values of the disk's optical depth the influence of ISM flow on the disk shape is almost negligible because the grains are collisionally destroyed before they can accumulate enough orbital changes due to the ISM perturbations. On the other hand, for values smaller than $10^{-3}$, peculiar asymmetric patterns appear in the density profile of the disk when we consider 1-10 mum grains, just above the blow-out threshold. The extent and relevance of these asymmetries grow for lower values of the optical depth. An additional sink mechanism, which may prevent the formation of large clumps and warping in the disks is related to the fast inward migration due to the drag component of the forces. When a significant eccentricity is pumped up by the ISM perturbations, the drag forces (Poynting-Robertson and in particular ISM drag) drive the disk particles on fast migrating tracks leading them into the star on a short timescale. It is then expected that disks with small optical depth expand inside the parent body ring all the way towards the star while disks with large optical depth would not significantly extend inside.Comment: accepted for publication in MNRA

A multifunctional cotton fabric using TiO2 and PCMs: introducing thermal comfort and self-cleaning properties

The development of materials with multiple functionalities is a market imperative that places new challenges on textile processing. Whatever the application, the goal is always to achieve the best performance with the simplest and most economically attractive process, without forgetting the sustainability issues. The purpose of this study is to establish the conditions to obtain by a simple method a cotton material with comfort, self-cleaning properties and antimicrobial activity. For that, microcapsules of phase change materials (PCMs) and TiO2 nanoparticles (NP) were applied conjugated and resulting fabrics were characterized by infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), contact angle and scanning electron microscopy with X-ray microanalysis (SEM/EDS). The self-cleaning properties of treated fabrics were also analyzed based on the photocatalytic ability of coated fabrics capability to decomposition of methyl orange (MO) under solar simulator irradiation [1] [1]and assessment of degradation of coffee, red wine and curry stains [2]. The comfort properties were assessed according DSC and Alambeta analysis. Moreover, incorporating TiO2 NP in the finishing formulation also was assessment the bacterial inhibition on the treated fabrics.CNPq-Brazil (Conselho Nacional de Desenvolvimento Científico e Tecnológico – Brasil / National Council of Scientific and Technological Development – Brazil) for the doctoral scholarship (233550/2014-3). Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007136 and Strategic Funding UID/Multi/04423/2013 by FCT and European Regional Development Fund (ERDF), in the framework of the programme PT2020.info:eu-repo/semantics/publishedVersio

L1 Interaction with Ankyrin Regulates Mediolateral Topography in the Retinocollicular Projection

Dynamic modulation of adhesion provided by anchorage of axonal receptors with the cytoskeleton contributes to attractant or repellent responses that guide axons to topographic targets in the brain. The neural cell adhesion molecule L1 engages the spectrin-actin cytoskeleton through reversible linkage of its cytoplasmic domain to ankyrin. To investigate a role for L1 association with the cytoskeleton in topographic guidance of retinal axons to the superior colliculus, a novel mouse strain was generated by genetic knock-in that expresses an L1 point mutation (Tyr1229His) abolishing ankyrin binding. Axon tracing revealed a striking mistargeting of mutant ganglion cell axons from the ventral retina, which express high levels of ephrinB receptors, to abnormally lateral sites in the contralateral superior colliculus, where they formed multiple ectopic arborizations. These axons were compromised in extending interstitial branches in the medial direction, a normal response to the high medial to low lateral SC gradient of ephrinB1. Furthermore, ventral but not dorsal L1(Y1229H) retinal cells were impaired for ephrinB1-stimulated adhesion through beta1 integrins in culture. The retinocollicular phenotype of the L1(Tyr1229His) mutant provides the first evidence that L1 regulates topographic mapping of retinal axons through adhesion mediated by linkage to the actin cytoskeleton and functional interaction with the ephrinB/EphB targeting system

Polysialylated NCAM and EphrinA/EphA regulate synaptic development of gabaergic interneurons in prefrontal cortex

A novel function for the neural cell adhesion molecule (NCAM) was identified in ephrinA/EphA-mediated repulsion as an important regulatory mechanism for development of GABAergic inhibitory synaptic connections in mouse prefrontal cortex. Deletion of NCAM, EphA3, or ephrinA2/3/5 in null mutant mice increased the numbers and size of perisomatic synapses between GABAergic basket interneurons and pyramidal cells in the developing cingulate cortex (layers II/III). A functional consequence of NCAM loss was increased amplitudes and faster kinetics of miniature inhibitory postsynaptic currents in NCAM null cingulate cortex. NCAM and EphA3 formed a molecular complex and colocalized with the inhibitory presynaptic marker vesicular GABA transporter (VGAT) in perisomatic puncta and neuropil in the cingulate cortex. EphrinA5 treatment promoted axon remodeling of enhanced green fluorescent protein-labeled basket interneurons in cortical slice cultures and induced growth cone collapse in wild-type but not NCAM null mutant neurons. NCAM modified with polysialic acid (PSA) was required to promote ephrinA5-induced axon remodeling of basket interneurons in cortical slices, likely by providing a permissive environment for ephrinA5/EphA3 signaling. These results reveal a new mechanism in which NCAM and ephrinAs/EphA3 coordinate to constrain GABAergic interneuronal arborization and perisomatic innervation, potentially contributing to excitatory/inhibitory balance in prefrontal cortical circuitry. © 2012 The Author