@article {1921, title = {New COL6A6 Variant Causes Autosomal Dominant Retinitis Pigmentosa in a Four-Generation Family.}, journal = {Invest Ophthalmol Vis Sci}, volume = {63}, year = {2022}, month = {2022 Mar 02}, pages = {23}, abstract = {

Purpose: To report that variants in the gene for a large lamina basal component protein, COL6A6 (collagen type VI alpha 6 chain, Col6α6), linked to chromosome 3p22.1 causes retinitis pigmentosa (RP) in patients with autosomal dominant transmission (adRP).

Methods: A positional-cloning approach, whole exome sequencing, and modeling were used. The proband and several affected family members have been phenotyped and followed for over 12 years.

Results: A heterozygous missense variant, c.509C\>G (p. Ser170Cys) in exon 2 of COL6A6 (comprised of 36 exons and 2236 amino acids), was observed in a four- generation family and is likely to cause the adRP phenotype. It was identified in 10 affected members. All affected family members had a distinct phenotype: late-onset rod cone dystrophy, with good retained visual acuity, until their late 70s. Immunohistochemistry of human retina showed a dot-like signal at the base of the inner segments of photoreceptors and outer plexiform layer (OPL). The structural modeling of the N7 domain of Col6α6 suggests that the mutant might result in the abnormal cellular localization of collagen VI or malformation of collagen fibers resulting in the loss of its unique filament structure.

Conclusions: COL6A6 is widely expressed in human tissues and evolutionary conserved. It is thought to interact with a range of extracellular matrix components. Our findings suggest that this form of RP has long-term useful central visual acuity and a mild progression, which are important considerations for patient counseling.

}, keywords = {Collagen Type VI, Cone-Rod Dystrophies, Exons, Humans, Mutation, Missense, Pedigree, Retinitis Pigmentosa}, issn = {1552-5783}, doi = {10.1167/iovs.63.3.23}, author = {Vaclavik, Veronika and Tiab, Leila and Sun, Young Joo and Mahajan, Vinit B and Moulin, Alexandre and Allaman-Pillet, Nathalie and Munier, Francis L and Schorderet, Daniel F} } @article {1091, title = {Optical Coherence Tomography Angiography of RPGR-Associated Retinitis Pigmentosa Suggests Foveal Avascular Zone is a Biomarker for Vision Loss.}, journal = {Ophthalmic Surg Lasers Imaging Retina}, volume = {50}, year = {2019}, month = {2019 02 01}, pages = {e44-e48}, abstract = {

RPGR-associated retinitis pigmentosa (RP) is a progressive disease with retina degeneration. Optical coherence tomography angiography (OCTA) is an imaging technique that provides novel insights. The authors report two affected male siblings who underwent OCTA imaging. The area of the foveal avascular zone (FAZ) was measured. Although the younger sibling exhibited more advanced clinical disease, his visual acuity was superior to his older sibling. OCTA imaging revealed a better preserved FAZ in the younger sibling as the reason for this. It also highlighted attenuation of choriocapillaris / choroid layers as biomarkers for disease severity. This provides new insights into retinal degeneration in RPGR-associated RP. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:e44-e48.].

}, keywords = {Biomarkers, Capillaries, Choroid, Eye Proteins, Fluorescein Angiography, Fovea Centralis, Humans, Male, Middle Aged, Retinitis Pigmentosa, Tomography, Optical Coherence, Vision Disorders}, issn = {2325-8179}, doi = {10.3928/23258160-20190129-18}, author = {Tang, Peter H and Jauregui, Ruben and Tsang, Stephen H and Bassuk, Alexander G and Mahajan, Vinit B} } @article {2047, title = {Therapeutic Window for Phosphodiesterase 6-Related Retinitis Pigmentosa.}, journal = {JAMA Ophthalmol}, volume = {137}, year = {2019}, month = {2019 Jun 01}, pages = {679-680}, keywords = {Cone-Rod Dystrophies, Cyclic Nucleotide Phosphodiesterases, Type 6, Eye Proteins, Follow-Up Studies, Humans, Mutation, Retinitis Pigmentosa}, issn = {2168-6173}, doi = {10.1001/jamaophthalmol.2018.6381}, author = {Wang, Nan-Kai and Mahajan, Vinit B and Tsang, Stephen H} } @article {655, title = {CRISPR Repair Reveals Causative Mutation in a Preclinical Model of Retinitis Pigmentosa.}, journal = {Mol Ther}, volume = {24}, year = {2016}, month = {2016 08}, pages = {1388-94}, abstract = {

Massive parallel sequencing enables identification of numerous genetic variants in mutant organisms, but determining pathogenicity of any one mutation can be daunting. The most commonly studied preclinical model of retinitis pigmentosa called the "rodless" (rd1) mouse is homozygous for two mutations: a nonsense point mutation (Y347X) and an intronic insertion of a leukemia virus (Xmv-28). Distinguishing which mutation causes retinal degeneration is still under debate nearly a century after the discovery of this model organism. Here, we performed gene editing using the CRISPR/Cas9 system and demonstrated that the Y347X mutation is the causative variant of disease. Genome editing in the first generation produced animals that were mosaic for the corrected allele but still showed neurofunction preservation despite low repair frequencies. Furthermore, second-generation CRISPR-repaired mice showed an even more robust rescue and amelioration of the disease. This predicts excellent outcomes for gene editing in diseased human tissue, as Pde6b, the mutated gene in rd1 mice, has an orthologous intron-exon relationship comparable with the human PDE6B gene. Not only do these findings resolve the debate surrounding the source of neurodegeneration in the rd1 model, but they also provide the first example of homology-directed recombination-mediated gene correction in the visual system.

}, keywords = {Animals, Clustered Regularly Interspaced Short Palindromic Repeats, CRISPR-Cas Systems, Cyclic Nucleotide Phosphodiesterases, Type 6, Disease Models, Animal, DNA Repair, Electroretinography, Exons, Gene Editing, Genetic Loci, Homologous Recombination, Mice, Mice, Transgenic, Mutation, Photoreceptor Cells, Vertebrate, Retinal Degeneration, Retinitis Pigmentosa, RNA, Guide}, issn = {1525-0024}, doi = {10.1038/mt.2016.107}, author = {Wu, Wen-Hsuan and Tsai, Yi-Ting and Justus, Sally and Lee, Ting-Ting and Zhang, Lijuan and Lin, Chyuan-Sheng and Bassuk, Alexander G and Mahajan, Vinit B and Tsang, Stephen H} } @article {637, title = {Reprogramming metabolism by targeting sirtuin 6 attenuates retinal degeneration.}, journal = {J Clin Invest}, volume = {126}, year = {2016}, month = {2016 Dec 01}, pages = {4659-4673}, abstract = {

Retinitis pigmentosa (RP) encompasses a diverse group of Mendelian disorders leading to progressive degeneration of rods and then cones. For reasons that remain unclear, diseased RP photoreceptors begin to deteriorate, eventually leading to cell death and, consequently, loss of vision. Here, we have hypothesized that RP associated with mutations in phosphodiesterase-6 (PDE6) provokes a metabolic aberration in rod cells that promotes the pathological consequences of elevated cGMP and Ca2+, which are induced by the Pde6 mutation. Inhibition of sirtuin 6 (SIRT6), a histone deacetylase repressor of glycolytic flux, reprogrammed rods into perpetual glycolysis, thereby driving the accumulation of biosynthetic intermediates, improving outer segment (OS) length, enhancing photoreceptor survival, and preserving vision. In mouse retinae lacking Sirt6, effectors of glycolytic flux were dramatically increased, leading to upregulation of key intermediates in glycolysis, TCA cycle, and glutaminolysis. Both transgenic and AAV2/8 gene therapy-mediated ablation of Sirt6 in rods provided electrophysiological and anatomic rescue of both rod and cone photoreceptors in a preclinical model of RP. Due to the extensive network of downstream effectors of Sirt6, this study motivates further research into the role that these pathways play in retinal degeneration. Because reprogramming metabolism by enhancing glycolysis is not gene specific, this strategy may be applicable to a wide range of neurodegenerative disorders.

}, keywords = {Animals, Cellular Reprogramming, Cellular Reprogramming Techniques, Citric Acid Cycle, Cyclic GMP, Cyclic Nucleotide Phosphodiesterases, Type 6, Dependovirus, Disease Models, Animal, Eye Proteins, Genetic Therapy, Glycolysis, Mice, Mice, Mutant Strains, Mutation, Retinal Rod Photoreceptor Cells, Retinitis Pigmentosa, Sirtuins, Transduction, Genetic}, issn = {1558-8238}, doi = {10.1172/JCI86905}, author = {Zhang, Lijuan and Du, Jianhai and Justus, Sally and Hsu, Chun-Wei and Bonet-Ponce, Luis and Wu, Wen-Hsuan and Tsai, Yi-Ting and Wu, Wei-Pu and Jia, Yading and Duong, Jimmy K and Mahajan, Vinit B and Lin, Chyuan-Sheng and Wang, Shuang and Hurley, James B and Tsang, Stephen H} } @article {641, title = {Reprogramming towards anabolism impedes degeneration in a preclinical model of retinitis pigmentosa.}, journal = {Hum Mol Genet}, volume = {25}, year = {2016}, month = {2016 10 01}, pages = {4244-4255}, abstract = {

Retinitis pigmentosa (RP) is an incurable neurodegenerative condition featuring photoreceptor death that leads to blindness. Currently, there is no approved therapeutic for photoreceptor degenerative conditions like RP and atrophic age-related macular degeneration (AMD). Although there are promising results in human gene therapy, RP is a genetically diverse disorder, such that gene-specific therapies would be practical in a small fraction of patients with RP. Here, we explore a non-gene-specific strategy that entails reprogramming photoreceptors towards anabolism by upregulating the mechanistic target of rapamycin (mTOR) pathway. We conditionally ablated the tuberous sclerosis complex 1 (Tsc1) gene, an mTOR inhibitor, in the rods of the Pde6bpreclinical RP mouse model and observed, functionally and morphologically, an improvement in the survival of rods and cones at early and late disease stages. These results elucidate the ability of reprogramming the metabolome to slow photoreceptor degeneration. This strategy may also be applicable to a wider range of neurodegenerative diseases, as enhancement of nutrient uptake is not gene-specific and is implicated in multiple pathologies. Enhancing anabolism promoted neuronal survival and function and could potentially benefit a number of photoreceptor and other degenerative conditions.

}, keywords = {Animals, Cell Death, Cellular Reprogramming, Cone-Rod Dystrophies, Disease Models, Animal, Humans, Macular Degeneration, Metabolism, Mice, Photoreceptor Cells, Retinal Cone Photoreceptor Cells, Retinal Rod Photoreceptor Cells, Retinitis Pigmentosa, TOR Serine-Threonine Kinases, Tumor Suppressor Proteins}, issn = {1460-2083}, doi = {10.1093/hmg/ddw256}, author = {Zhang, Lijuan and Justus, Sally and Xu, Yu and Pluchenik, Tamara and Hsu, Chun-Wei and Yang, Jin and Duong, Jimmy K and Lin, Chyuan-Sheng and Jia, Yading and Bassuk, Alexander G and Mahajan, Vinit B and Tsang, Stephen H} } @article {713, title = {Quantitative autofluorescence as a clinical tool for expedited differential diagnosis of retinal degeneration.}, journal = {JAMA Ophthalmol}, volume = {133}, year = {2015}, month = {2015 Feb}, pages = {219-20}, keywords = {Adult, ATP-Binding Cassette Transporters, Diagnosis, Differential, DNA, DNA Mutational Analysis, Fluorescein Angiography, Fundus Oculi, Humans, Male, Mutation, Optical Imaging, Retina, Retinal Degeneration, Retinitis Pigmentosa}, issn = {2168-6173}, doi = {10.1001/jamaophthalmol.2014.4507}, author = {Marsiglia, Marcela and Lee, Winston and Mahajan, Vinit B and Zernant, Jana and Delori, Fran{\c c}ois C and Tsang, Stephen H and Sparrow, Janet R} } @article {707, title = {Silencing of tuberin enhances photoreceptor survival and function in a preclinical model of retinitis pigmentosa (an american ophthalmological society thesis).}, journal = {Trans Am Ophthalmol Soc}, volume = {112}, year = {2014}, month = {2014 Jul}, pages = {103-15}, abstract = {

PURPOSE: To assess the functional consequences of silencing of tuberin, an inhibitor of the mTOR signaling pathway, in a preclinical model of retinitis pigmentosa (RP) in order to test the hypothesis that insufficient induction of the protein kinase B (PKB)-regulated tuberin/mTOR self-survival pathway initiates apoptosis.

METHODS: In an unbiased genome-scale approach, kinase peptide substrate arrays were used to analyze self-survival pathways at the onset of photoreceptor degeneration. The mutant Pde6b(H620Q)/Pde6b(H620Q) at P14 and P18 photoreceptor outer segment (OS) lysates were labeled with P-ATP and hybridized to an array of 1,164 different synthetic peptide substrates. At this stage, OS of Pde6b(H620Q)/Pde6b(H620Q) rods are morphologically normal. In vitro kinase assays and immunohistochemistry were used to validate phosphorylation. Short hairpin RNA (shRNA) gene silencing was used to validate tuberin{\textquoteright}s role in regulating survival.

RESULTS: At the onset of degeneration, 162 peptides were differentially phosphorylated. Protein kinases A, G, C (AGC kinases), and B exhibited increased activity in both peptide array and in vitro kinase assays. Immunohistochemical data confirmed altered phosphorylation patterns for phosphoinositide-dependent kinase-1 (PDK1), ribosomal protein S6 (RPS6), and tuberin. Tuberin gene silencing rescued photoreceptors from degeneration.

CONCLUSIONS: Phosphorylation of tuberin and RPS6 is due to the upregulated activity of PKB. PKB/tuberin cell growth/survival signaling is activated before the onset of degeneration. Substrates of the AGC kinases in the PKB/tuberin pathway are phosphorylated to promote cell survival. Knockdown of tuberin, the inhibitor of the mTOR pathway, increased photoreceptor survival and function in a preclinical model of RP.

}, keywords = {Animals, Apoptosis, Disease Models, Animal, Gene Silencing, Mice, Mice, Mutant Strains, Phosphorylation, Phosphotransferases, Proto-Oncogene Proteins c-akt, Retinitis Pigmentosa, Ribosomal Protein S6, Signal Transduction, Tumor Suppressor Proteins}, issn = {1545-6110}, author = {Tsang, Stephen H and Chan, Lawrence and Tsai, Yi-Ting and Wu, Wen-Hsuan and Hsu, Chun-Wei and Yang, Jin and Tosi, Joaquin and Wert, Katherine J and Davis, Richard J and Mahajan, Vinit B} }