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June 17, 2022 | Université de Genève Journal Reference Olivier Mercey, Corinne Kostic, Eloïse Bertiaux, Alexia Giroud, Yashar Sadian, David C. A. Gaboriau, Ciaran G. Morrison, Ning Chang, Yvan Arsenijevic, Paul Guichard, Virginie Hamel. The connecting cilium inner scaffold provides a structural foundation that protects against retinal degeneration . PLOS Biology , 2022; 20 (6): e3001649 DOI: 10.1371/journal.pbio.3001649 Summary Retinitis pigmentosa, a degenerative genetic disease of the eye, is characterized by progressive vision loss, usually leading to blindness. In some patients, structural defects in the photoreceptor cells have been observed, but the molecular mechanisms involved are not understood. A team has identified the essential role played by a molecular zipper formed by four proteins. The absence of this zipper leads to cell death in retinal cells. This discovery could lead to the development of therapeutic approaches for retinitis pigmentosa. Article Retinitis pigmentosa, a degenerative genetic disease of the eye, is characterized by progressive vision loss, usually leading to blindness. In some patients, structural defects in the photoreceptor cells have been observed, but the molecular mechanisms involved are not understood. A team from the University of Geneva (UNIGE), in collaboration with the University of Lausanne (UNIL), has identified the essential role played by a molecular zipper formed by four proteins. The absence of this zipper leads to cell death in retinal cells. This discovery could lead to the development of therapeutic approaches for retinitis pigmentosa. This work can be read in the journal PLOS Biology . Click here to read full article

Advanced Drug Delivery Review ; Volume 62, Issue 7-8, 15 June 2010, Pg 741-752 Eduardo Anitua Mikel Sánchez Gorka Orivea Abstract Endogenous regenerative technology (Endoret) involves the use of patient's own biologically active proteins, growth factors and biomaterial scaffolds for therapeutic purposes. This technology provides a new approach for the stimulation and acceleration of tissue healing and bone regeneration. The versatility and biocompatibility of using patient-derived fibrin scaffold as an autologous, biocompatible and biodegradable drug delivery system open the door to a personalized medicine that is currently being used in numerous medical and scientific fields including dentistry, oral implantology, orthopaedics, ulcer treatment, sports medicine and tissue engineering among others. This review discusses the state of the art and new directions in the use of endogenous technology in the repair and regeneration of injured tissues by means of a controlled and local protein and growth factor delivery. The next generations of engineering strategies together with some of the most interesting therapeutic applications are discussed together with the future challenges in the field. Click link to access original article .

Josephine Prener Holtan ,  Knut Teigen ,  Ingvild Aukrust ,  Ragnheiður Bragadóttir ,  Gunnar Houge | Ophthalmic Genetics | April 1, 2019 | Volume 40(2) | Pages 124-128 | DOI: 10.1080/13816810.2019.1586965 Purpose To clinically and genetically characterize a second family with dominant ARL3-related retinitis pigmentosa due to a specific ARL3 missense variant, p.(Tyr90Cys). Methods Clinical examination included optical coherence tomography, electroretinography, and ultra-wide field retinal imaging with autofluorescence. Retrospective data were collected from the registry of inherited retinal diseases at Oslo university hospital. DNA was analyzed by whole-exome sequencing and Sanger sequencing. The ARL3 missense variant was visualized in a 3D-protein structure. Results The phenotype was non-syndromic retinitis pigmentosa with cataract associated with early onset of decreased central vision and central retinal thinning. Sanger sequencing confirmed the presence of a de novo ARL3 missense variant p.(Tyr90Cys) in the index patient and his affected son. We did not find any other cases with rare ARL3 variants in a cohort of 431 patients with retinitis pigmentosa-like disease. By visualizing Tyr90 in the 3D protein structure, it seems to play an important role in packing of the α/β structure of ADP-ribosylation factor-like 3 (ARL3). When changing Tyr90 to cysteine, we observe a loss of interactions in the core of the α/β structure that is likely to affect folding and stability of ARL3. Conclusion Our study confirms that the ARL3 missense variant p.(Tyr90Cys) causes retinitis pigmentosa. In 2016, Strom et al. reported the exact same variant in a mother and two children with RP, labelled?RP83 in the OMIM database. Now the question mark can be removed, and ARL3 should be added to the list of genes that may cause non-syndromic dominant retinitis pigmentosa. To purchase full article, click here

Zhimeng Zhang, Hehua Dai, Lei Wang, Tianchang Tao, Jing Xu, Xiaowei Sun, Liping Yang, Genlin Li | BMC Ophthalmology | Vol. 19, Article # 240 | 2019 | Background RP (retinitis pigmentosa) is a group of hereditary retinal degenerative diseases. XLRP is a relatively severe subtype of RP. Thus, it is necessary to identify genes and mutations in patients who present with X-linked retinitis pigmentosa. Methods Genomic DNA was extracted from peripheral blood. The coding regions and intron-exon boundaries of the retinitis pigmentosa GTPase regulator (RPGR) and RP2 genes were amplified by PCR and then sequenced directly. Ophthalmic examinations were performed to identify affected individuals from two families and to characterize the phenotype of the disease. Results Mutation screening demonstrated two novel nonsense mutations (c.1541C > G; p.S514X and c.2833G > T; p.E945X) in the RPGR gene. The clinical manifestation of family 1 with mutations in exon 13 was mild. Genotype-phenotype correlation analysis suggested that patients with mutations close to the downstream region of ORF15 in family 2 manifested an early loss of cone function. Family 2 carried a nonsense mutation in ORF15 that appeared to have a semi-dominant pattern of inheritance. All male patients and two female carriers in family 2 manifested pathological myopia (PM), indicating that there may be a distinctive X-linked genotype-phenotype correlation between RP and PM. Conclusions We identified two novel mutations of the RPGR gene, which broadens the spectrum of RPGR mutations and the phenotypic spectrum of the disease in Chinese families. Read the complete article

Chunbo Yang, Maria Georgiou, Robert Atkinson, Joseph Collin, Jumana Al-Aama, Sushma Nagaraja-Grellscheid, Colin Johnson, Robin Ali, Lyle Armstrong, Sina Mozaffari-Jovin, and Majlinda Lako | doi.org/10.3389/fcell.2021.700276 Overview Retinitis pigmentosa (RP) is the most common inherited retinal disease characterized by progressive degeneration of photoreceptors and/or retinal pigment epithelium that eventually results in blindness. Mutations in pre-mRNA processing factors ( PRPF3, PRPF4, PRPF6, PRPF8, PRPF31, SNRNP200, and RP9 ) have been linked to 15–20% of autosomal dominant RP (adRP) cases. Current evidence indicates that PRPF mutations cause retinal specific global spliceosome dysregulation, leading to mis-splicing of numerous genes that are involved in a variety of retina-specific functions and/or general biological processes, including phototransduction, retinol metabolism, photoreceptor disk morphogenesis, retinal cell polarity, ciliogenesis, cytoskeleton and tight junction organization, waste disposal, inflammation, and apoptosis. Importantly, additional PRPF functions beyond RNA splicing have been documented recently, suggesting a more complex mechanism underlying PRPF -RPs driven disease pathogenesis. The current review focuses on the key RP- PRPF genes, depicting the current understanding of their roles in RNA splicing, impact of their mutations on retinal cell’s transcriptome and phenome, discussed in the context of model species including yeast, zebrafish, and mice. Importantly, information on PRPF functions beyond RNA splicing are discussed, aiming at a holistic investigation of PRPF -RP pathogenesis. Finally, work performed in human patient-specific lab models and developing gene and cell-based replacement therapies for the treatment of PRPF -RPs are thoroughly discussed to allow the reader to get a deeper understanding of the disease mechanisms, which we believe will facilitate the establishment of novel and better therapeutic strategies for PRPF -RP patients. Introduction Retinitis pigmentosa (RP) is the most common group of inherited retinal disorders characterized by progressive degeneration of photoreceptors and/or the retinal pigment epithelium (RPE). Most RP cases start with night blindness due to the breakdown of rod photoreceptors, which are responsible for night vision. As the disease progresses, mid-peripheral vision is lost (tunnel vision), followed by cone degeneration leading to central vision loss until eventual blindness ( Hartong et al., 2006 ; Berger et al., 2010 ). The prevalence of RP is around 1 in 4000 and there are over 1.5 million people suffering from this condition worldwide ( Verbakel et al., 2018 ). There is no cure for RP although vitamins, nutritional supplementation and small molecules may slow disease progression. To date, more than 70 genetic loci have been involved in the pathogenesis of RP 1 . Approximately half of RP cases have previous family history and fall into three Mendelian modes of inheritance: autosomal recessive (arRP), autosomal dominant (adRP), and X-linked recessive (xlRP) ( Hamel, 2006 ). 50–60% of RP cases are caused by autosomal-recessive inheritance, 30–40% of cases are autosomal dominant, and 5–15% of cases are X-linked. Most of the genes involved in RP ontology are expressed specifically in the retina and/or RPE and contribute to photoreceptor or RPE function. Mutations in the rhodopsin ( RHO ) gene are the most common cause of adRP accounting for 25% of adRP cases. Interestingly, the second most common cause of adRP accounting for 15–20% of adRP cases, is linked to mutations in the ubiquitously expressed pre-mRNA processing factor ( PRPF ) genes, that encode core components of the spliceosome ( Wang et al., 2019 ). Read the entire article References Berger, W., Kloeckener-Gruissem, B., and Neidhardt, J. (2010). The molecular basis of human retinal and vitreoretinal diseases. Prog. Retin. Eye Res. 29, 335–375. Hamel, C. (2006). Retinitis pigmentosa. Orphanet. J. Rare Dis. 1:40. Hartong, D. T., Berson, E. L., and Dryja, T. P. (2006). Retinitis pigmentosa. Lancet 368, 1795–1809. Verbakel, S. K., Van Huet, R. A. C., Boon, C. J. F., Den Hollander, A. I., Collin, R. W. J., Klaver, C. C. W., et al. (2018). Non-syndromic retinitis pigmentosa. Prog. Retin. Eye Res. 66, 157–186. Wang, A. L., Knight, D. K., Vu, T. T., and Mehta, M. C. (2019). Retinitis pigmentosa: review of current treatment. Int. Ophthalmol. Clin. 59, 263–280.

By Arlene Weintraub Mutations in more than 270 genes have been implicated in inherited eye diseases like retinitis pigmentosa. Now, Biogen has formed a research pact with Harvard’s Massachusetts Eye and Ear that’s aimed at developing a gene therapy to help some patients with these blinding diseases. The gene at the center of the new agreement, PRPF31, has been linked to autosomal dominant retinitis pigmentosa. PRPF31 mutations are believed to cause an estimated 25% of all retinitis pigmentosa cases. The partners did not disclose the financial terms of the deal. The tie-up comes eight months after a Mass Eye and Ear team published preclinical research demonstrating a gene therapy technique for repairing cells with mutated PRPF31 genes. The technique partially restored the structure and function of retinal pigment epithelium cells, the team reported in the journal Molecular Therapy Methods & Clinical Development. The research was led by Eric Pierce, M.D., Ph.D., professor at Harvard Medical School and director of the inherited retinal disorders service at Mass Eye and Ear. Read the entire article

Molecular Analysis and Detailed Phenotypic Study Abstract Purpose: To report novel variants and characterize the phenotype associated with the autosomal recessive retinal dystrophy caused by mutations in the lecithin retinol acyltransferase ( LRAT ) gene. Methods: A total of 149 patients with Leber's congenital amaurosis (LCA) or early onset retinal dystrophy were screened for mutations in LCA-associated genes using an arrayed-primer extension (APEX) genotyping microarray (Asper Ophthalmics). LRAT sequencing was subsequently performed in this 148-patient panel. Patients identified with mutations underwent further detailed phenotyping. Results: APEX analysis identified one patient with a previously reported homozygous LRAT mutation. Sequencing of the panel identified three additional patients with novel homozygous LRAT mutations in exon 2. All four patients had severe progressive nyctalopia, visual field constriction, and photophilia in childhood. Visual acuity ranged from 0.22 logMAR to hand motion. Funduscopy revealed severe retinal pigment epithelial atrophy and minimal retinal pigmentation. Asteroid hyalosis and macular epiretinal fibrosis were frequent. All demonstrated reduced fundus autofluorescence. Optical coherence tomography identified disrupted retinal lamination, outer-retinal debris, and an unidentifiable photoreceptor layer in two cases. Full-field electroretinograms were undetectable or showed severe rod-cone dysfunction. Photopic perimetry revealed severe visual field constriction. Dark-adapted perimetry demonstrated markedly reduced photoreceptor sensitivity. Dark-adapted spectral sensitivity measurements identified functioning rods in two of three patients. All three had severely reduced L- and M-cone sensitivity and poor color discrimination. Conclusions: LRAT mutations cause a severe, early childhood onset, progressive retinal dystrophy. Phenotypic similarities to the retinal dysfunction associated with RPE-specific protein 65 kDa mutations, another visual cycle gene, suggest that LRAT deficiency may show a good response to novel therapies. To read the entire article, click here . Investigative Ophthalmology & Visual Science June 2012, Vol.53, 3927-3938. doi: https://doi.org/10.1167/iovs.12-9548

Sawar Zahid MS, MD, Kari Branham MS, CGC, Dana Schlegel MS, MPH, CGC, Mark E. Pennesi MD, PhD, Michel Michaelides MB, MD, John Heckenlively MD & Thiran Jayasundera MD | Jun 26, 2018 | In: Retinal Dystrophy Gene Atlas | Abstract LRAT encodes lecithin retinol acyltransferase, which catalyzes the earlier reactions in the retinoid visual pathway in the retinal pigment epithelium (RPE). Recessive mutations in LRAT cause a spectrum of disease that ranges from Leber congenital amaurosis (LCA) to forms of “juvenile” or “early-onset” retinitis pigmentosa (RP) that present slightly later in life (1–3). Read the article: doi.org/10.1007/978-3-319-10867-4_44 References Thompson DA, Li Y, McHenry CL, Carlson TJ, Ding X, Sieving PA, et al. Mutations in the gene encoding lecithin retinol acyltransferase are associated with early-onset severe retinal dystrophy. National Genetics . 2001;28(2):123–4. Senechal A, Humbert G, Surget MO, Bazalgette C, Bazalgette C, Arnaud B, et al. Screening genes of the retinoid metabolism: novel LRAT mutation in leber congenital amaurosis. American Journal Ophthalmology . 2006; 142(4):702–4. den Hollander AI, Lopez I, Yzer S, Zonneveld MN, Janssen IM, Strom TM, et al. Identification of novel mutations in patients with Leber congenital amaurosis and juvenile RP by genome-wide homozygosity mapping with SNP microarrays. Invest Ophthalmology Vision Sciences . 2007 48(12):5690–8.

Céline Koster, Koen T. van den Hurk, Colby F. Lewallen, Mays Talib, Jacoline B. ten Brink, Camiel J. F. Boon, Arthur A. Bergen | International Journal of Molecular Sciences | July 5, 2021 | Vol. 22, Issue 13 | 7234 | doi: 10.3390/ijms22137234 Abstract Purpose: We developed and phenotyped a pigmented knockout rat model for lecithin retinol acyltransferase (LRAT) using CRISPR/Cas9. The introduced mutation (c.12delA) is based on a patient group harboring a homologous homozygous frameshift mutation in the LRAT gene (c.12delC), causing a dysfunctional visual (retinoid) cycle. Methods: The introduced mutation was confirmed by DNA and RNA sequencing. The expression of Lrat was determined on both the RNA and protein level in wildtype and knockout animals using RT-PCR and immunohistochemistry. The retinal structure and function, as well as the visual behavior of the Lrat −/− and control rats, were characterized using scanning laser ophthalmoscopy (SLO), optical coherence tomography (OCT), electroretinography (ERG) and vision-based behavioral assays. Results: Wildtype animals had high Lrat mRNA expression in multiple tissues, including the eye and liver. In contrast, hardly any expression was detected in Lrat −/− animals. LRAT protein was abundantly present in wildtype animals and absent in Lrat −/− animals. Lrat −/− animals showed progressively reduced ERG potentials compared to wildtype controls from two weeks of age onwards. Vison-based behavioral assays confirmed reduced vision. Structural abnormalities, such as overall retinal thinning, were observed in Lrat −/− animals. The retinal thickness in knockout rats was decreased to roughly 80% by four months of age. No functional or structural differences were observed between wildtype and heterozygote animals. Conclusions: Our Lrat −/− rat is a new animal model for retinal dystrophy, especially for the LRAT -subtype of early-onset retinal dystrophies. This model has advantages over the existing mouse models and the RCS rat strain and can be used for translational studies of retinal dystrophies. Introduction Retinitis pigmentosa (RP), Leber congenital amaurosis (LCA), and retinitis punctata albescens (RPA) are severe early-onset retinal dystrophies that cause visual impairment, nystagmus, progressive nyctalopia, and finally, blindness. This heterogeneous retinal dystrophy disease group is characterized by damage to the retinal pigment epithelium (RPE)–photoreceptor (PR) complex. This results usually in progressive dysfunction of the rod photoreceptor cells, often followed by progressive cone degeneration. RP, LCA, and RPA are caused by mutations in virtually all genes encoding proteins acting in the retinoid cycle ( 1 , 2 , 3 , 4 ). Indeed, for normal vision, a functionally valid retinoid cycle is essential: In the healthy situation, vitamin A (retinol) is the primary substrate for several functional retinoids’ biosynthesis in the retinoid cycle. Then, the vitamin A-derivatives are shuttled from the RPE to the PRs. There, opsins are light-activated and the visual pigments transform the light energy in a cellular signal, initiating the visual cascade and resulting in a physiological response in the PR cell. After light activation, the cycle regenerates the visual pigments that are used after light activation of rhodopsin (see Figure 1 ). Upon photoactivation, a configurational change of the visual pigment 11- cis -retinal to all- trans -retinal is induced in the PR cells’ outer segments. Subsequently, all- trans -retinal is reduced to all- trans -retinol and diffuses from the PRs back to to the RPE cells. In the RPE, all- trans -retinol is esterified to all- trans -retinyl-ester by the enzyme lecithin:retinol acetyltransferase (LRAT), after which all- trans -retinyl-ester is subsequently the substrate for the enzyme retinal pigment epithelium-specific protein 65 kDa (RPE65). RPE65 converts all- trans -retinyl-ester to 11- cis -retinol, after which 11- cis -retinol is oxidized by retinol dehydrogenase (RDH) enzymes to 11- cis -retinal. Finally, to complete the cycle, 11- cis -retinal is shuttled back to the PRs, where it can be used for a new round of phototransduction. Read the article References 1. Chelstowska S., Widjaja-Adhi M.A.K., Silvaroli J.A., Golczak M. Impact of LCA-Associated E14L LRAT Mutation on Protein Stability and Retinoid Homeostasis. Biochemistry. 2017;56:4489–4499. doi: 10.1021/acs.biochem.7b00451. 2. Den Hollander A.I., Lopez I., Yzer S., Zonneveld M.N., Janssen I.M., Strom T.M., Hehir-Kwa J.Y., Veltman J.A., Arends M.L., Meitinger T., et al. Identification of novel mutations in patients with Leber congenital amaurosis and juvenile RP by genome-wide homozygosity mapping with SNP microarrays. Investig. Ophthalmol. Vis. Sci. 2007;48:5690–5698. doi: 10.1167/iovs.07-0610. 3. Dev Borman A., Ocaka L.A., Mackay D.S., Ripamonti C., Henderson R.H., Moradi P., Hall G., Black G.C., Robson A.G., Holder G.E., et al. Early onset retinal dystrophy due to mutations in LRAT: Molecular analysis and detailed phenotypic study. Investig. Ophthalmol. Vis. Sci. 2012;53:3927–3938. doi: 10.1167/iovs.12-9548. 4. Littink K.W., van Genderen M.M., van Schooneveld M.J., Visser L., Riemslag F.C., Keunen J.E., Bakker B., Zonneveld M.N., den Hollander A.I., Cremers F.P., et al. A homozygous frameshift mutation in LRAT causes retinitis punctata albescens. Ophthalmology. 2012;119:1899–1906. doi: 10.1016/j.ophtha.2012.02.037.

By Jeff Hansen | June 10, 2020 Researchers who made a knock-in mouse-model of the genetic disorder retinitis pigmentosa 59, or RP59, expected to see retinal degeneration and retinal thinning. As reported in the journal Cells, they surprisingly found none, calling into question the commonly accepted — though never proved — mechanism for RP59. “Our findings bring into question the current concept that RP59 is a member of a large and diverse class of diseases known as ‘congenital disorders of glycosylation,’” said Steven Pittler, Ph.D., professor and director of the University of Alabama at Birmingham School of Optometry and Vision Science Vision Science Research Center. “While in principle it would be reasonable to consider RP59 as a congenital disorder of glycosylation, due to the associated mutation in DHDDS, an enzyme required for glycosylation, there is no direct evidence to demonstrate a glycosylation defect in the human retinal disease or in any animal model of RP59 generated to date.” Read the article Researchers at UAB, SUNY-Buffalo and the Polish Academy of Sciences did the study.

Byron L Lam, Stephan L Züchner, Julia Dallman, Rong Wen, Eduardo C Alfonso, Jeffery M Vance, Margaret A Peričak-Vance |  Advances in Experimental Medicine and Biology  book series |  2014 Jan 1 | vol. 801 | 165-70 | doi: 10.1007/978-1-4614-3209-8_21 A single-nucleotide mutation in the gene that encodes DHDDS has been identified by whole exome sequencing as the cause of the non-syndromic recessive retinitis pigmentosa (RP) in a family of Ashkenazi Jewish origin in which three of the four siblings have early onset retinal degeneration. The peripheral retinal degeneration in the affected siblings was evident in the initial examination in 1992 and only one had detectable electroretinogram (ERG) that suggested cone-rod dysfunction. Read more, click here

Isabelle Perrault , Jean-Michel Rozet , Sylvie Gerber , Imad Ghazi , Corinne Leowski , Dominique Ducroq , Eric Souied , Jean-Louis Dufier , Arnold Munnich , Josseline Kaplan | Molecular Genetics and Metabolism | Volume 68, Issue 2 | October 1999 | Pages 200-208 Abstract Leber's congenital amaurosis (LCA) is the earliest and most severe form of all inherited retinal dystrophies responsible for congenital blindness. Genetic heterogeneity of LCA has been suspected since the report by Waardenburg of normal children born to affected parents. In 1995, we localized the first disease causing gene, LCA1, to chromosome 17p13 and confirmed the genetic heterogeneity. In 1996, we ascribed LCA1 to mutations in the photoreceptor-specific guanylate cyclase gene (retGC1). RetGC1 is an essential protein implicated in the phototransduction cascade, especially in the recovery of the dark state after the excitation process of photoreceptor cells by light stimulation. In 1997, mutations in a second gene were reported in LCA, the RPE65 gene, which is the first specific retinal pigment epithelium gene. The protein RPE65 is implicated in the metabolism of vitamin A, the precursor of the photoexcitable retinal pigment (rhodopsin). Finally, a third gene, CRX, implicated in photoreceptor development, has been suspected of causing a few cases of LCA. Taken together, these three genes account for only 27% of LCA cases in our series. The three genes encode proteins that are involved in completely different physiopathologic pathways. Based on these striking differences of physiopathologic processes, we reexamined all clinical physiopathological discrepancies and the results strongly suggested that retGC1 gene mutations are responsible for congenital stationary severe cone–rod dystrophy, while RPE65 gene mutations are responsible for congenital severe but progressive rod–cone dystrophy. It is of tremendous importance to confirm and to refine these genotype–phenotype correlations on a large scale in order to anticipate the final outcome in a blind infant, on the one hand, and to further guide genetic studies in older patients on the other hand. To purchase paper, follow this link