Search results for " PHOTOTRANSDUCTION"
showing 10 items of 18 documents
Rhythmic Regulation of Photoreceptor and RPE Genes Important for Vision and Genetically Associated With Severe Retinal Diseases.
2018
Purpose The aim of the present study was to identify candidate genes for mediating daily adjustment of vision. Methods Genes important for vision and genetically associated with severe retinal diseases were tested for 24-hour rhythms in transcript levels in neuronal retina, microdissected photoreceptors, photoreceptor-related pinealocytes, and retinal pigment epithelium-choroid (RPE-choroid) complex by using quantitative PCR. Results Photoreceptors of wildtype mice display circadian clock-dependent regulation of visual arrestins (Arr1, Arr4) and the visual cycle gene Rdh12, whereas cells of the RPE-choroid exhibit light-dependent regulation of the visual cycle key genes Lrat, Rpe65, and Rdh…
Peripherin-2 differentially interacts with cone opsins in outer segments of cone photoreceptors
2016
Peripherin-2 is a glycomembrane protein exclusively expressed in the light-sensing compartments of rod and cone photoreceptors designated as outer segments (OS). Mutations in peripherin-2 are associated with degenerative retinal diseases either affecting rod or cone photoreceptors. While peripherin-2 has been extensively studied in rods, there is only little information on its supramolecular organization and function in cones. Recently, we have demonstrated that peripherin-2 interacts with the light detector rhodopsin in OS of rods. It remains unclear, however, if peripherin-2 also binds to cone opsins. Here, using a combination of co-immunoprecipitation analyses, transmission electron micr…
Mutations in the Cone Photoreceptor G-Protein α-Subunit Gene GNAT2 in Patients with Achromatopsia
2002
Achromatopsia is an autosomal recessively inherited visual disorder that is present from birth and that features the absence of color discrimination. We here report the identification of five independent families with achromatopsia that segregate protein-truncation mutations in the GNAT2 gene, located on chromosome 1p13. GNAT2 encodes the cone photoreceptor-specific alpha-subunit of transducin, a G-protein of the phototransduction cascade, which couples to the visual pigment(s). Our results demonstrate that GNAT2 is the third gene implicated in achromatopsia.
Functional analysis of Normal and CSNB a-wave ERG component
2009
The features of a-wave of the human electroretinogram are one of the more debated problems in electrophysiology since the a-wave reflects the functional integrity of the two photoreceptoral populations (rods and cones). Although different models concerning the contributions of the early photoreceptoral response are available in current literature, a fully comprehensive theory is difficult to formulate because of the large amount of individual photoreceptors. We study the kinetics of the photoreceptoral response through the analysis of the a-wave shape both in healthy and in patients affected by the Congenital Stationary Night Blindness, that interests the rod population only. The physiologi…
Functional Characterization of a Guanylyl Cyclase-activating Protein from Vertebrate Rods
1996
The membrane-bound guanylyl cyclase in vertebrate photoreceptor cells is one of the key enzymes in visual transduction. It is highly sensitive to the free calcium concentration ([Ca2+]). The activation process is cooperative and mediated by a novel calcium-binding protein named GCAP (guanylyl cyclase-activating protein). We isolated GCAP from bovine rod outer segments, determined amino acid sequences of proteolytically obtained peptides, and cloned its gene. The Ca2+-bound form of native GCAP has an apparent molecular mass of 20.5 kDa and the Ca2+-free form of 25 kDa as determined by SDS-polyacrylamide gel electrophoresis. Recombinant GCAP was functionally expressed in Escherichia coli. Act…
Indoor artificial lighting: Prediction of the circadian effects of different spectral power distributions.
2014
The study presented in this paper aims to evaluate if and how the environment affects the circadian impact of a light source by predicting circadian stimulus (CS) resulting from the exposure to different light scenes, using equations reported in studies by Rea et al. The main findings are: (1) Above 600 lx at eye level the increase of CS is little; (2) Between 50 lx and 200 lx at the eye level an increase of only 50 lx determines a significant increase of CS; (3) Light sources with correlated colour temperatures between 2900 K and 4200 K have similar impacts on the circadian system according to the calculation method used; (4) Even an almost neutral environment affects the circadian impact…
ApoB100,LDLR-/- mice exhibit reduced electroretinographic response and cholesteryl esters deposits in the retina
2008
International audience; PURPOSE. To evaluate the retinal phenotype of 7- and 14-month-old apoB100,LDLR–/– mice, a relevant animal model of lipid metabolism dysfunction. METHODS. Single-flash electroretinograms were obtained from 7- and 14-month-old apoB100,LDLR–/– and control mice fed a standard diet under both scotopic and photopic conditions. Visual cycle retinoids were analyzed in eyes from dark-adapted mice. Retinal and choroidal vascularization was evaluated with scanning laser ophthalmoscopy. Fatty acids were analyzed in the retina. Esterified and free cholesterol was detected in eye cryosections. RESULTS. Scotopic and photopic b-wave amplitudes were significantly reduced in apoB100,L…
Mouse photoreceptor synaptic ribbons lose and regain material in response to illumination changes
2004
Abstract Chemical synapses equipped with ribbons are tonically active, high-output synapses. The ribbons may play a role in the trafficking of synaptic vesicles. Recent findings in retinal rod cells of BALB/c mice indicate that ribbons are large and smooth in the dark phase, and, due to the formation and release of protrusions, small during the light phase. As a consequence of these changes, ribbons may traffick fewer vesicles in the light than in the dark phases. The aim of the present study was to find out whether the above ribbon changes in this mouse strain are strictly illumination-dependent and which signalling processes may be involved. Here, we show that ribbons form protrusions and…
A mouse model of in vivo chemical inhibition of retinal calcium-independent phospholipase A2 (iPLA2).
2013
International audience; Numerous studies have reported the implication of calcium-independent phospholipase A2 (iPLA2) in various biological mechanisms. Most of these works have used in vitro models and only a few have been carried out in vivo on iPLA2(-/-) mice. The functions of iPLA2 have been investigated in vivo in the heart, brain, pancreatic islets, and liver, but not in the retina despite its very high content in phospholipids. Phospholipids in the retina are known to be involved in several various key mechanisms such as visual transduction, inflammation or apoptosis. In order to investigate the implication of iPLA2 in these processes, this work was aimed to build an in vivo model of…
Transcriptional analysis of rat photoreceptor cells reveals daily regulation of genes important for visual signaling and light damage susceptibility.
2013
Photoreceptor cells face the challenge of adjusting their function and, possibly, their susceptibility to light damage to the marked daily changes in ambient light intensity. To achieve a better understanding of photoreceptor adaptation at the transcriptional level, this study aimed to identify genes which are under daily regulation in photoreceptor cells using microarray analysis and quantitative PCR. Included in the gene set obtained were a number of genes which up until now have not been shown to be expressed in photoreceptor cells, such as Atf3 (activating transcription factor 3) and Pde8a (phosphodiesterase 8A), and others with a known impact on phototransduction and/or photoreceptor s…