In vivo phenotypic and molecular characterization of retinal degeneration in mouse models of three ciliopathies

International audienceCilia are highly conserved and ubiquitously expressed organelles. Ciliary defects of genetic origins lead to ci-liopathies, in which retinal degeneration (RD) is one cardinal clinical feature. In order to efficiently find and design new therapeutic strategies the underlying mechanism of retinal degeneration of three murine model was compared. The rodent models correspond to three emblematic ciliopathies, namely: Bardet-Biedl Syndrome (BBS), Alström Syndrome (ALMS) and CEP290-mediated Leber Congenital Amaurosis (LCA). Scotopic rodent electroretinography (ERG) was used to test the retinal function of mice, Transmitted Electron microscopy (T.E.M) was performed to assess retinal structural defects and real-time PCR for targeted genes was used to monitor the expression levels of the major apoptotic Caspase-related pathways in retinal extracts to identify pathological pathways driving the RD in order to identify potential therapeutic targets. We found that BBS and CEP290-mediated LCA mouse models exhibit perinatal retinal degeneration associated with rhodopsin mis-localization in the photoreceptor and the induction of an Endoplasmic Reticulum (ER) stress. On the other hand, the tested ALMS mouse model, displayed a slower degeneration phenotype, with no Rhodopsin mislocalization nor ER-stress activity. Our data points out that behind the general phenotype of vision loss associated with these ciliopathies, the mechanisms and kinetics of disease progression are different

Complexation du Ca++ par les substances humiques extraites de tourbe naturelle et de tourbe traitée aux oxydes d'azote

The study of the complexation of calcium by humic substances (SH) extracted from a natural peat (TN) and from a peat treated with nitrogen oxides (TT) was followed by conductimetry and potentiometry with pH variable and pH constant. The complexing capacity increases as the pH rises: complexed calcium is 130 cmol kg*[-1) SH (TN) and 135 cmol kg*[-1) SH (TT) with pH 5, and 330 cmol kg*[-1) SH (TN) and 410 cmol kg*[-1) SH (TT) with pH 9. These reactions involve various functional groupings of pKa1 < 4 for TN and TT, pKa2 = 5.9 for TN and pKa2 = 6.2 for TT; in all cases, the medium has exhibited an increase in acidity. The complexation of calcium by HS extracted from TT could then enhance the efficiency of the phosphatic nutrition of plants

Mild forms of hypophosphatasia mostly result from dominant negative effect of severe alleles or from compound heterozygosity for severe and moderate alleles

<p>Abstract</p> <p>Background</p> <p>Mild hypophosphatasia (HPP) phenotype may result from <it>ALPL </it>gene mutations exhibiting residual alkaline phosphatase activity or from severe heterozygous mutations exhibiting a dominant negative effect. In order to determine the cause of our failure to detect a second mutation by sequencing in patients with mild HPP and carrying on a single heterozygous mutation, we tested the possible dominant effect of 35 mutations carried by these patients.</p> <p>Methods</p> <p>We tested the mutations by site-directed mutagenesis. We also genotyped 8 exonic and intronic <it>ALPL </it>gene polymorphisms in the patients and in a control group in order to detect the possible existence of a recurrent intronic mild mutation.</p> <p>Results</p> <p>We found that most of the tested mutations exhibit a dominant negative effect that may account for the mild HPP phenotype, and that for at least some of the patients, a second mutation in linkage disequilibrium with a particular haplotype could not be ruled out.</p> <p>Conclusion</p> <p>Mild HPP results in part from compound heterozygosity for severe and moderate mutations, but also in a large part from heterozygous mutations with a dominant negative effect.</p

Rho1 regulates apoptosis via activation of the JNK signaling pathway at the plasma membrane

In the absence of moesin, RhoA slips out of its normal role as a GTPase to activate the JNK MAPK pathway and spur apoptosis

Physiologically relevant reconstitution of iron-sulfur cluster biosynthesis uncovers persulfide- processing functions of ferredoxin-2 and frataxin

Iron-sulfur (Fe-S) clusters are essential protein cofactors whose biosynthetic defects lead to severe diseases among which is Friedreich's ataxia caused by impaired expression of frataxin (FXN). Fe-S clusters are biosynthesized on the scaffold protein ISCU, with cysteine desulfurase NFS1 providing sulfur as persulfide and ferredoxin FDX2 supplying electrons, in a process stimulated by FXN but not clearly understood. Here, we report the breakdown of this process, made possible by removing a zinc ion in ISCU that hinders iron insertion and promotes non-physiological Fe-S cluster synthesis from free sulfide in vitro. By binding zinc-free ISCU, iron drives persulfide uptake from NFS1 and allows persulfide reduction into sulfide by FDX2, thereby coordinating sulfide production with its availability to generate Fe-S clusters. FXN stimulates the whole process by accelerating persulfide transfer. We propose that this reconstitution recapitulates physiological conditions which provides a model for Fe-S cluster biosynthesis, clarifies the roles of FDX2 and FXN and may help develop Friedreich's ataxia therapies

The c.429_452 duplication of the ARX gene: a unique developmental-model of limb kinetic apraxia:

BACKGROUND: The c.429_452dup24 of the ARX gene is a rare genetic anomaly, leading to X-Linked Intellectual Disability without brain malformation. While in certain cases c.429_452dup24 has been associated with specific clinical patterns such as Partington syndrome, the consequence of this mutation has been also often classified as "non-specific Intellectual Disability". The present work aims at a more precise description of the clinical features linked to the c.429_452dup24 mutation. METHODS: We clinically reviewed all affected patients identified in France over a five-year period, i.e. 27 patients from 12 different families. Detailed cognitive, behavioural, and motor evaluation, as well as standardized videotaped assessments of oro-lingual and gestural praxis, were performed. In a sub-group of 13 ARX patients, kinematic and MRI studies were further accomplished to better characterize the motor impairment prevalent in the ARX patients group. To ensure that data were specific to the ARX gene mutation and did not result from low-cognitive functioning per se, a group of 27 age- and IQ-matched Down syndrome patients served as control. RESULTS: Neuropsychological and motor assessment indicated that the c.429_452dup24 mutation constitutes a recognizable clinical syndrome: ARX patients exhibiting Intellectual Disability, without primary motor impairment, but with a very specific upper limb distal motor apraxia associated with a pathognomonic hand-grip. Patients affected with the so-called Partington syndrome, which involves major hand dystonia and orolingual apraxia, exhibit the most severe symptoms of the disorder. The particular "reach and grip" impairment which was observed in all ARX patients, but not in Down syndrome patients, was further characterized by the kinematic data: (i) loss of preference for the index finger when gripping an object, (ii) major impairment of fourth finger deftness, and (iii) a lack of pronation movements. This lack of distal movement coordination exhibited by ARX patients is associated with the loss of independent digital dexterity and is similar to the distortion of individual finger movements and posture observed in Limb Kinetic Apraxia. CONCLUSION: These findings suggest that the ARX c.429_452dup24 mutation may be a developmental model for Limb Kinetic Apraxia

Développement de thérapies pharmacologiques innovantes dans le traitement des dégénérescences rétiniennes héréditaires

Retinitis pigmentosa is the first cause of inherited retinal degeneration affecting 1.5 million persons worldwide. Currently, there is no available treatment for most of these diseases. Based on a previous study, the project aims to develop a treatment for some of them. The tested approach targets a common cellular pathway activated in many of these diseases; the Unfolded Protein Response (UPR), pathway activated in response to a stress due to a protein overload. The treatment decreases this overload. is the treatment is composed of IFB-088, a GADD34/PP1c inhibitor, allowing maintaining the translation inhibition and of valproic acid which increases BiP and the folding capacities of the reticulum. The treatment was tested in two models displaying UPR activation. In these models, the treatment slow-down the short-term retinal degeneration by decreasing cellular stress to maintain visual capacities.Les rétinopathies pigmentaires sont la première cause de dégénérescence rétinienne héréditaire, affectant 1,5 millions de personnes dans le monde. A ce jour, aucun traitement n’est disponible dans la majorité de ces pathologies. Basé sur une étude antérieure, le projet vise au développement d’un traitement dans certaines d’entre elles. L’approche testée cible une voie activée dans plusieurs de ces atteintes ; l’Unfolded Protein Response (UPR), mécanisme de réponse au stress activée en particulier an cas de surcharge protéique. Le traitement permet de diminuer cette charge protéique. Il est composé d’IFB-088, inhibiteur du complexe GADD34/PP1c, permettant le maintien de l’inhibition de la traduction induit par l’UPR et d’acide valproïque stimulant BiP et les capacités de repliement du réticulum. Il a été testé dans deux modèles présentant une activation de l’UPR. Les résultats ont montré qu’il pouvait ralentir la dégénérescence rétinienne à court terme, réduisant le stress cellulaire et maintenant les capacités visuelles

Conséquences cardiovasculaires du syndrome d'apnées obstructives du sommeil (étude chez 51 patients avant et après traitement par pression positive continue)

GRENOBLE1-BU Médecine pharm. (385162101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF