A Sweet Talk: The Molecular Systems of Perineuronal Nets in Controlling Neuronal Communication

Perineuronal nets (PNNs) are mesh-like structures, composed of a hierarchical assembly of extracellular matrix molecules in the central nervous system (CNS), ensheathing neurons and regulating plasticity. The mechanism of interactions between PNNs and neurons remain uncharacterized. In this review, we pose the question: how do PNNs regulate communication to and from neurons? We provide an overview of the current knowledge on PNNs with a focus on the cellular interactions. PNNs ensheath a subset of the neuronal population with distinct molecular aspects in different areas of the CNS. PNNs control neuronal communication through molecular interactions involving specific components of the PNNs. This review proposes that the PNNs are an integral part of neurons, crucial for the regulation of plasticity in the CNS

Chondroitin sulfates and their binding molecules in the central nervous system

Chondroitin sulfate (CS) is the most abundant glycosaminoglycan (GAG) in the central nervous system (CNS) matrix. Its sulfation and epimerization patterns give rise to different forms of CS, which enables it to interact specifically and with a significant affinity with various signalling molecules in the matrix including growth factors, receptors and guidance molecules. These interactions control numerous biological and pathological processes, during development and in adulthood. In this review, we describe the specific interactions of different families of proteins involved in various physiological and cognitive mechanisms with CSs in CNS matrix. A better understanding of these interactions could promote a development of inhibitors to treat neurodegenerative diseases

Chapter 3 Transplantation of GABAergic interneurons for cell-based therapy

Many neurological disorders stem from defects in or the loss of specific neurons. Neuron transplantation has tremendous clinical potential for central nervous system therapy as it may allow for the targeted replacement of those cells that are lost in diseases. Normally, most neurons are added during restricted periods of embryonic and fetal development. The permissive milieu of the developing brain promotes neuronal migration, neuronal differentiation, and synaptogenesis. Once this active period of neurogenesis ends, the chemical and physical environment of the brain changes dramatically. The brain parenchyma becomes highly packed with neuronal and glial processes, extracellular matrix, myelin, and synapses. The migration of grafted cells to allow them to home into target regions and become functionally integrated is a key challenge to neuronal transplantation. Interestingly, transplanted young telencephalic inhibitory interneurons are able to migrate, differentiate, and integrate widely throughout the postnatal brain. These grafted interneurons can also functionally modify local circuit activity. These features have facilitated the use of interneuron transplantation to study fundamental neurodevelopmental processes including cell migration, cell specification, and programmed neuronal cell death. Additionally, these cells provide a unique opportunity to develop interneuron-based strategies for the treatment of diseases linked to interneuron dysfunction and neurological disorders associated to circuit hyperexcitability

Direct-detection wind lidar operating with a multimode laser

International audienceA direct-detection wind lidar that operates with a multimode laser has been developed and tested. The instrument exploits the light backscattered by particles using a Mach-Zehnder interferometer with an optical path difference matched to the free spectral range of the laser longitudinal modes. In addition to requiring no monomodal emission, the system requires no frequency locking between the interferometer and the laser. We report laboratory and atmospheric measurements that show that the lidar is capable of measuring the radial wind velocity with a systematic error lower than 1 ms(-1) and a random error lower than 2 ms(-1) for a signal-to-noise ratio of 100. The development is motivated by the possibility to probe wind with a compact system in planetary atmospheres

355-nm high spectral resolution airborne lidar LNG: system description and first results

International audienceA high spectral resolution (HSR) measurement capability in the ultraviolet has been added to the 3-wavelength-2-polarization-backscatter lidar LNG (lidar aerosols nouvelle génération) and tested during several flights. The system includes a Mach–Zehnder interferometer (MZI) as a spectral discriminator and does not require any frequency locking between the emitter and the interferometer. Results obtained during test flights show that the backscatter and extinction coefficients at 355 nm can be measured with a relative precision of 10% for 60 m and 240 m vertical resolution, respectively, in aerosol layers of 10−6m−1 sr−1 backscatter coefficient with a 30-km horizontal resolution. The same relative precision is obtained in cirrus clouds of a 2×10−5m−1sr−1 backscatter coefficient for the same vertical resolution and a horizontal resolution reduced to 5 km. The capacity of the system to perform wind velocity measurements is also demonstrated with precisions in the range of 1 to 2  ms−1. Particle-to-total backscatter ratio and line-of-sight speed measurements have been performed on ground echoes; averaged data show biases less than 1% and 0.15  ms−1, respectively

Development/Plasticity/Repair Otx2 Binding to Perineuronal Nets Persistently Regulates Plasticity in the Mature Visual Cortex

International audienceSpecific transfer of (orthodenticle homeobox 2) Otx2 homeoprotein into GABAergic interneurons expressing parvalbumin (PV) is necessary and sufficient to open, then close, a critical period (CP) of plasticity in the developing mouse visual cortex. The accumulation of endogenous Otx2 in PV cells suggests the presence of specific Otx2 binding sites. Here, we find that perineuronal nets (PNNs) on the surfaces of PV cells permit the specific, constitutive capture of Otx2. We identify a 15 aa domain containing an arginine-lysine doublet (RK peptide) within Otx2, bearing prototypic traits of a glycosaminoglycan (GAG) binding sequence that mediates Otx2 binding to PNNs, and specifically to chondroitin sulfate D and E, with high affinity. Accordingly, PNN hydrolysis by chondroitinase ABC reduces the amount of endogenous Otx2 in PV cells. Direct infusion of RK peptide similarly disrupts endogenous Otx2 localization to PV cells, reduces PV and PNN expression, and reopens plasticity in adult mice. The closure of one eye during this transient window reduces cortical acuity and is specific to the RK motif, as an Alanine-Alanine variant or a scrambled peptide fails to reactivate plasticity. Conversely, this transient reopening of plasticity in the adult restores binocular vision in amblyopic mice. Thus, one function of PNNs is to facilitate the persistent internalization of Otx2 by PV cells to maintain CP closure. The pharmacological use of the Otx2 GAG binding domain offers a novel, potent therapeutic tool with which to restore cortical plasticity in the mature brain

Broadband Submillimeter Receivers Using Same Mechanical Block

International audienceWe present the performances of two sensitive submillimeter receivers operating in distinct bandwidth ranges: 330-540 GHz and 430-660 GHz, by using a unique robust, assembly-friendly, space-qualified fix-tuned mixer block. Only the corrugated horns and SIS devices have been swapped. The Fourier Transform Spectrometry measurements show 50% frequency bandwidth and the uncorrected measured DSB noise temperatures were less than 7 times the quantum limit in both cases. Index TermsFix-tuned mixer block, twin SIS junction, broad bandwidths