L'éducation scientifique, l'éducation à l'environnement et l'éducation pour le développement durable. Croisements, enjeux et mouvances

Dans la perspective d’enrichir l’éducation scientifique d’une dimension citoyenne, et plus spécifi quement écocitoyenne, la prise en compte des questions socioécologiques requiert l’intégration dans les curriculums de sciences, d’objectifs relevant d’une éducation relative à l’environnement. Or, le contexte actuel de promotion du développement durable (DD) à l’échelle nationale et internationale fait appel au recadrage de l’éducation à l’environnement dans une perspective de DD. Le projet planétaire d’éducation pour le développement durable (ÉDD) propose d’axer désormais l’effort éducatif, non pas sur le rapport à l’environnement et la reconstruction du réseau des relations au milieu de vie, mais sur l’avènement d’un « développement » que l’on souhaite durable. Dans un tel contexte de mouvance curriculaire, de prescriptions ministérielles, de débats et de controverses, ce numéro d’Aster se penche sur les enjeux que soulèvent l’intégration de préoccupations environnementales et la visée du développement durable à l’enseignement des sciences. Dans un premier temps, nous effectuerons un bref rappel historique des étapes clés de l’évolution de l’éducation à l’environnement en France ; ce faisant, nous mettrons en évidence ses liens avec les curriculums de sciences. Nous situerons ensuite cette trajectoire nationale dans une dynamique internationale, où le développement durable s’impose comme un cadre de référence incontournable. Notre survol de ce paysage éducatif en évolution constante, dans le creuset des transformations sociales contemporaines, nous amènera à ouvrir une fenêtre de réfl exion sur le croisement de l’enseignement de sciences avec l’éducation relative à l’environnement et l’éducation pour le développement durable. Enfi n, nous verrons quels éclairages apportent sur cette question les auteurs de ce numéro d’Aster

Correlation between SD-OCT, immunocytochemistry and functional findings in an animal model of retinal degeneration

Purpose: The P23H rhodopsin mutation is an autosomal dominant cause of retinitis pigmentosa (RP). The degeneration can be tracked using different anatomical and functional methods. In our case, we evaluated the anatomical changes using Spectral-Domain Optical Coherence Tomography (SD-OCT) and correlated the findings with retinal thickness values determined by immunocytochemistry.Methods: Pigmented rats heterozygous for the P23H mutation, with ages between P18 and P180 were studied. Function was assessed by means of optomotor testing and ERGs. Retinal thicknesses measurements, autofluorescence and fluorescein angiography were performed using Spectralis OCT. Retinas were studied by means of immunohistochemistry. Results: Between P30 and P180, visual acuity decreased from 0.500 to 0.182 cycles per degree (cyc/deg) and contrast sensitivity decreased from 54.56 to 2.98 for a spatial frequency of 0.089 cyc/deg. Only cone-driven b-wave responses reached developmental maturity. Flicker fusions were also comparable at P29 (42 Hz). Double flash-isolated rod-driven responses were already affected at P29. Photopic responses revealed deterioration after P29.A reduction in retinal thicknesses and morphological modifications were seen in OCT sections. Statistically significant differences were found in all evaluated thicknesses. Autofluorescence was seen in P23H rats as sparse dots. Immunocytochemistry showed a progressive decrease in the outer nuclear layer (ONL), and morphological changes. Although anatomical thickness measures were significantly lower than OCT values, there was a very strong correlation between the values measured by both techniques.Conclusions: In pigmented P23H rats, a progressive deterioration occurs in both retinal function and anatomy. Anatomical changes can be effectively evaluated using SD-OCT and immunocytochemistry, with a good correlation between their values, thus making SD-OCT an important tool for research in retinal degeneration.Dr. Pinilla and Dr. Cuenca were supported by grants from the Spanish Ministry of Economy and Competitiveness-FEDER (BFU2012-36845), Instituto de Salud Carlos III (FIS PI13/01124, PS0901854, PI042399 and RETICS RD12/0034/0010), Fundación Gangoiti, ONCE (Organización Nacional de Ciegos Españoles) and FUNDALUCE. Dr. Yves Sauvé is a recipient of the Barbara Tuck/MacPhee Family Vision Research Award in Macular Degeneration

Cell-Type Specific Roles for PTEN in Establishing a Functional Retinal Architecture

BACKGROUND: The retina has a unique three-dimensional architecture, the precise organization of which allows for complete sampling of the visual field. Along the radial or apicobasal axis, retinal neurons and their dendritic and axonal arbors are segregated into layers, while perpendicular to this axis, in the tangential plane, four of the six neuronal types form patterned cellular arrays, or mosaics. Currently, the molecular cues that control retinal cell positioning are not well-understood, especially those that operate in the tangential plane. Here we investigated the role of the PTEN phosphatase in establishing a functional retinal architecture. METHODOLOGY/PRINCIPAL FINDINGS: In the developing retina, PTEN was localized preferentially to ganglion, amacrine and horizontal cells, whose somata are distributed in mosaic patterns in the tangential plane. Generation of a retina-specific Pten knock-out resulted in retinal ganglion, amacrine and horizontal cell hypertrophy, and expansion of the inner plexiform layer. The spacing of Pten mutant mosaic populations was also aberrant, as were the arborization and fasciculation patterns of their processes, displaying cell type-specific defects in the radial and tangential dimensions. Irregular oscillatory potentials were also observed in Pten mutant electroretinograms, indicative of asynchronous amacrine cell firing. Furthermore, while Pten mutant RGC axons targeted appropriate brain regions, optokinetic spatial acuity was reduced in Pten mutant animals. Finally, while some features of the Pten mutant retina appeared similar to those reported in Dscam-mutant mice, PTEN expression and activity were normal in the absence of Dscam. CONCLUSIONS/SIGNIFICANCE: We conclude that Pten regulates somal positioning and neurite arborization patterns of a subset of retinal cells that form mosaics, likely functioning independently of Dscam, at least during the embryonic period. Our findings thus reveal an unexpected level of cellular specificity for the multi-purpose phosphatase, and identify Pten as an integral component of a novel cell positioning pathway in the retina

Protection of Visual Functions by Human Neural Progenitors in a Rat Model of Retinal Disease

BACKGROUND: A promising clinical application for stem and progenitor cell transplantation is in rescue therapy for degenerative diseases. This strategy seeks to preserve rather than restore host tissue function by taking advantage of unique properties often displayed by these versatile cells. In studies using different neurodegenerative disease models, transplanted human neural progenitor cells (hNPC) protected dying host neurons within both the brain and spinal cord. Based on these reports, we explored the potential of hNPC transplantation to rescue visual function in an animal model of retinal degeneration, the Royal College of Surgeons rat. METHODOLOGY/PRINCIPAL FINDINGS: Animals received unilateral subretinal injections of hNPC or medium alone at an age preceding major photoreceptor loss. Principal outcomes were quantified using electroretinography, visual acuity measurements and luminance threshold recordings from the superior colliculus. At 90–100 days postnatal, a time point when untreated rats exhibit little or no retinal or visual function, hNPC-treated eyes retained substantial retinal electrical activity and visual field with near-normal visual acuity. Functional efficacy was further enhanced when hNPC were genetically engineered to secrete glial cell line-derived neurotrophic factor. Histological examination at 150 days postnatal showed hNPC had formed a nearly continuous pigmented layer between the neural retina and retinal pigment epithelium, as well as distributed within the inner retina. A concomitant preservation of host cone photoreceptors was also observed. CONCLUSIONS/SIGNIFICANCE: Wild type and genetically modified human neural progenitor cells survive for prolonged periods, migrate extensively, secrete growth factors and rescue visual functions following subretinal transplantation in the Royal College of Surgeons rat. These results underscore the potential therapeutic utility of hNPC in the treatment of retinal degenerative diseases and suggest potential mechanisms underlying their effect in vivo

Modified Cav1.4 Expression in the Cacna1fnob2 Mouse Due to Alternative Splicing of an ETn Inserted in Exon 2

The Cacna1fnob2 mouse is reported to be a naturally occurring null mutation for the Cav1.4 calcium channel gene and the phenotype of this mouse is not identical to that of the targeted gene knockout model. We found two mRNA species in the Cacna1fnob2 mouse: approximately 90% of the mRNA represents a transcript with an in-frame stop codon within exon 2 of CACNA1F, while approximately 10% of the mRNA represents a transcript in which alternative splicing within the ETn element has removed the stop codon. This latter mRNA codes for full length Cav1.4 protein, detectable by Western blot analysis that is predicted to differ from wild type Cav1.4 protein in a region of approximately 22 amino acids in the N-terminal portion of the protein. Electrophysiological analysis with either mouse Cav1.4wt or Cav1.4nob2 cDNA revealed that the alternatively spliced protein does not differ from wild type with respect to activation and inactivation characteristics; however, while the wild type N-terminus interacted with filamin proteins in a biochemical pull-down experiment, the alternatively spliced N-terminus did not. The Cacna1fnob2 mouse electroretinogram displayed reduced b-wave and oscillatory potential amplitudes, and the retina was morphologically disorganized, with substantial reduction in thickness of the outer plexiform layer and sprouting of bipolar cell dendrites ectopically into the outer nuclear layer. Nevertheless, the spatial contrast sensitivity (optokinetic response) of Cacna1fnob2 mice was generally similar to that of wild type mice. These results suggest the Cacna1fnob2 mouse is not a CACNA1F knockout model. Rather, alternative splicing within the ETn element can lead to full-length Cav1.4 protein, albeit at reduced levels, and the functional Cav1.4 mutant may be incapable of interacting with cytoskeletal filamin proteins. These changes, do not alter the ability of the Cacna1fnob2 mouse to detect and follow moving sine-wave gratings compared to their wild type counterparts

Reformation of functional synapses in the retino-collicular pathway of adult hamsters

The functional reconstruction of interrupted CNS pathways in mature mammals was studied in adult hamsters in which retinal ganglion cells (RGCs) regenerated axons through a peripheral nerve graft directed from the stump of the cut optic nerve to the superior colliculus (SC). Visually elicited unitary responses of both pre- and postsynaptic origin were recorded in the reinnervated SC and were discriminated by selectively abolishing postsynaptic activity using GABA microiontophoresis. Activity from individual regenerated axonal arbors and from the neurons within their terminal field of innervation was confined to the superficial retinorecipient SC layers and could be recorded over a range of up to 200 $mu$m in all planes. Analysis of such electrophysiological recordings suggests that the terminal arborizations of single regenerated RGC axons can establish functional synapses with several SC neurons and that the convergence of inputs from regenerated RGC axons is not required for the activation of SC neurons in response to light. Functional synapses established between regenerated RGC axons and SC neurons persisted for up to 60 weeks after grafting. Visually elicited responses were recorded in the contralateral SC from the regenerated projections of as many as 63 different RGCs. The extent of functional innervation by regenerated retinal axons accessing the SC at a single entry point covered up to 0.8 mm and 1.2 mm in the caudo-rostral and latero-medial planes, respectively. Despite large scale targeting errors in the functional reinnervation of the SC, the re-established retinal projections in the SC were not randomly deployed along the caudo-rostral axis. There was an overall tendency for the relative naso-temporal position of any two RGCs to be appropriately represented by their respective regenerated inputs in the SC along its caudo-rostral axis. This suggests that regenerating RGC axons may recognize caudo-rostral positional markers as they reinnervate the SC

Les Enjeux éthiques des politiques publics en matière d'environnement.

International audienc

Enjeux éthiques des politiques publiques en matière d'environnement

International audienc

L'éducation à l'environnement ou au développement durable /

Publ. comme no 46, 2008 de la revue Aster