Most monogenic forms of inherited retinopathies are associated with genes expressed in photoreceptors (PR) or retinal pigment epithelium (RPE) where they encode proteins that are critical for PR structure, function and survival. Specific cellular processes and biochemical pathways implicated in retinal dystrophies include: PR development, morphogenesis, photo transduction, visual cycle, cellular metabolism, protein folding, among others. The vision and survival of rod and cone require continuous renewal of the visual chromophore, the 11-cis retinal, which forms together with the opsin proteins, the rhodopsin and cone visual pigments.

 

Img1-Brabet11-cis retinal is produced from vitamin A, an all-trans retinol, which is supplied with provitamin carotene from diet. In the outer segment (OS) discs of PR, light cause photoisomerization of 11-cis-retinal to all-trans-retinal, this is then reduced to all-trans retinol. Renewal of 11-cis retinal is provided by the visual cycle, an enzymatic pathway which involves the adjacent RPE and Müller cells. Stargardt pathophysiology involves rapid accumulation of toxic bisretinoid by-products such as A2E in the RPE.     

 

 

 

 

 

 

 

Scientific production

Our team has identified several mutations in the visual cycle genes responsible for retinal dystrophies (Marlhens et al., Nat Genet, 1997; Sénéchal et al., Am J Ophthalmol. 2006; Humbert et al., Invest Ophthalmol Vis Sci. 2006; Ksantini et al., Ophthalmic Genet. 2010). We have now developed biochemical analysis and animal models to study molecular mechanisms and pathophysiology of the visual cycle. We’ve started up the strategies by searching for retinoid isomerase (RPE65)-interacting proteins. A two-hybrid screening with the bait RPE65 has revealed several classes of proteins that can interact with. Among them, the metabolic protein FATP1 is an acyl-CoA-synthetase which mobilizes long chain fatty acid. We demonstrated the co-expression of FATP1 and RPE65 in cell cultures results in significant inhibition of 11-cis-retinol formation (Guignard et al., JBC, 2010). This was the first demonstration of a RPE65 interacting protein which inhibits the isomerisation. We then studied the phenotype of Fatp1-deficient mice provided by Andreas Stahl. Interestingly, these mice showed a slight but significant decrease of the visual function and several retinal alterations with age (Chekroud et al., PLoS One. 2012). Transgenic mice overexpressing the human FATP1 gene in RPE are currently investigated.

 

Proposals

                1- Lipid metabolism is of major importance for retina integrity and its deregulation can lead to pigmentary retinopathies. Lipid disorders have been implicated in macular degeneration such as the age-related macular degeneration (AMD) and Stargardt disease. Loss of function of fatp gene, the orthologue of FATP1 in drosophila, leads to PR death (Dourlen, P et al., PLoS genetics 2012). We propose to study the conserved functions of Fatp genes in drosophila and mice and the mechanisms by which lipid deregulations lead to perturbation of PR function and survival.

              2- The carbonyl and oxidative stress (COS) play a substantial role in Stargardt disease as well as in aging pathologies like age-related macular degeneration (AMD). We will develop chemicals that should be efficient as anti-COS: first, to slow down the formation of bis-retinoid derivatives, such as A2E, by quenching excess of all-trans-retinal in the photoreceptor cells, second, to quench oxidant stressors avoiding damages related to oxidation of A2E in the RPE.Strength of our expertise in the biochemistry of the retina and the visual cycle, we will work on post-genomic projects for studying new gene mutations and analyzing phenotype of new animal models for gene therapy. These post-genomics will be further extended to new genes identified by genetic analysis for perse retinal dystrophies.

 

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Technical Expertises

Biochemistry and molecular biology, yeast two-hydrid screening, recombinant protein interaction, cell cultures, cell death and cell survival measurements, HLPC analysis of retinoids, analytical chemistry to probe the visual cycle, physiology of the visual function in mice.

 

 

 

 

 

Major publications

Van des Brink D.M., et al., Plos Genet, 14(9):e1007627, 2018
Cubizolle A., et alPLoS One. 12(7): e0180148, 2017
Cia D., et al., J Mol Cell Med. 20(9): 1651-63, 2016
Crauste C., et al., European J Org Chem, 21, 4548-4561, 2014
Manes G., et al., PLoS One, 9(4):e95768, 2014
Manes G., et al., Am J Hum Genet, 93(3):571-8, 2013
Chekroud K., et al., PLoS One, 7(11):e50231, 2012
Guignard TJ., et al., J Biol Chem, 285(24):18759-68, 2010

 

Collaborations

  • Bertrand Mollereau (Equipe Apoptose et Neurogénétique, ENS de Lyon).
  • David Cia (UMR Inserm 1107, Laboratoire de Biophysique Neurosensorielle, Facultés de Médecine et de Pharmacie, Clermont-Ferrand).
  • Céline Crauste, Joseph Vercauteren et Thierry Durand, Institute of Biomolecules Max Mousseron (IBMM), UMR5247-CNRS-UM1-UM2-ENSCM, Faculty of Pharmacy, Montpellier.
  • Peter Humphries, Ocular Genetics Unit, Department of Genetics, Trinity College Dublin, Dublin, Ireland.

 

Fundings

ANR 1Retina FranceStargardt

Contact

Brabet Philippe