@article {2020, title = {Expanding the phenotype of TTLL5-associated retinal dystrophy: a case series.}, journal = {Orphanet J Rare Dis}, volume = {17}, year = {2022}, month = {2022 04 01}, pages = {146}, abstract = {

BACKGROUND: Inherited retinal dystrophies describe a heterogeneous group of retinal diseases that lead to the irreversible degeneration of rod and cone photoreceptors and eventual blindness. Recessive loss-of-function mutations in Tubulin Tyrosine Ligase Like 5 (TTLL5) represent a recently described cause of inherited cone-rod and cone dystrophy. This study describes the unusual phenotypes of three patients with autosomal recessive mutations in TTLL5. Examination of these patients included funduscopic evaluation, spectral-domain optical coherence tomography, short-wavelength autofluorescence, and full-field electroretinography (ffERG). Genetic diagnoses were confirmed using whole exome capture. Protein modeling of the identified variants was performed to explore potential genotype-phenotype correlations.

RESULTS: Genetic testing revealed five novel variants in TTLL5 in three unrelated patients with retinal dystrophy. Clinical imaging demonstrated features of sectoral cone-rod dystrophy and cone dystrophy, with phenotypic variability seen across all three patients. One patient also developed high-frequency hearing loss during a similar time period as the onset of retinal disease, potentially suggestive of a syndromic disorder. Retinal structure findings were corroborated with functional measures including ffERG findings that supported these diagnoses. Modeling of the five variants suggest that they cause different effects on protein function, providing a potential reason for genotype-phenotype correlation in these patients.

CONCLUSIONS: The authors report retinal phenotypic findings in three unrelated patients with novel mutations causing autosomal recessive TTLL5-mediated retinal dystrophy. These findings broaden the understanding of the phenotypes associated with TTLL5-mediated retinal disease and suggest that mutations in TTLL5 should be considered as a potential cause of sectoral retinal dystrophy in addition to cone-rod and cone dystrophies.

}, keywords = {Carrier Proteins, Electroretinography, Genetic Association Studies, Humans, Mutation, Phenotype, Retinal Dystrophies}, issn = {1750-1172}, doi = {10.1186/s13023-022-02295-9}, author = {Oh, Jin Kyun and Vargas Del Valle, Jos{\'e} G and Lima de Carvalho, Jose Ronaldo and Sun, Young Joo and Levi, Sarah R and Ryu, Joseph and Yang, Jing and Nagasaki, Takayuki and Emanuelli, Andres and Rasool, Nailyn and Allikmets, Rando and Sparrow, Janet R and Izquierdo, Natalio J and Duncan, Jacque L 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 {163, title = {Patients with an acute zonal occult outer retinopathy-like illness rapidly improve with valacyclovir treatment.}, journal = {American journal of ophthalmology}, volume = {150}, year = {2010}, month = {2010 Oct}, pages = {511-8}, abstract = {

To describe 3 cases of an acute zonal occult outer retinopathy-like illness responsive to valacyclovir hydrochloride.

}, keywords = {Acute Disease, Acyclovir, Adolescent, Adult, Antiviral Agents, Electroretinography, Eye Infections, Viral, Female, Herpesviridae Infections, Humans, Male, Retinal Diseases, Retrospective Studies, Scotoma, Tomography, Optical Coherence, Valine, Visual Field Tests, Visual Fields}, author = {Mahajan, Vinit B and Stone, Edwin M} } @article {173, title = {A new macular dystrophy with anomalous vascular development, pigment spots, cystic spaces, and neovascularization.}, journal = {Archives of ophthalmology}, volume = {127}, year = {2009}, month = {2009 Nov}, pages = {1449-57}, abstract = {

To clinically phenotype an inherited macular dystrophy with peculiar intraretinal pigment spots, cysts, and hemorrhage in a 24-year-old female proband and her family.

}, keywords = {Adolescent, Adult, Amblyopia, Child, Child, Preschool, Cysts, Electroretinography, Female, Fluorescein Angiography, Humans, Macular Degeneration, Male, Middle Aged, Pedigree, Phenotype, Retinal Hemorrhage, Retinal Neovascularization, Retinal Pigment Epithelium, Retinal Vessels, Strabismus, Tomography, Optical Coherence, Visual Acuity, Young Adult}, author = {Mahajan, Vinit B and Russell, Stephen R and Stone, Edwin M} } @article {177, title = {Transgenic mice carrying the H258N mutation in the gene encoding the beta-subunit of phosphodiesterase-6 (PDE6B) provide a model for human congenital stationary night blindness.}, journal = {Human mutation}, volume = {28}, year = {2007}, month = {2007 Mar}, pages = {243-54}, abstract = {

Mutations in the beta-subunit of cGMP-phosphodiesterase (PDE6beta) can lead to either progressive retinal disease, such as human retinitis pigmentosa (RP), or stationary disease, such as congenital stationary night blindness (CSNB). Individuals with CSNB in the Rambusch pedigree were found to carry the H258N allele of PDE6B (MIM$\#$ 180072); a similar mutation was not found in RP patients. This report describes an individual carrying the H258N allele, who presented with generalized retinal dysfunction affecting the rod system and a locus of dysfunction at the rod-bipolar interface. Also described are preclinical studies in which transgenic mice with the H258N allele were generated to study the pathophysiological mechanisms of CSNB. While Pde6b(rd1)/Pde6b(rd1) mice have severe photoreceptor degeneration, as in human RP, the H258N transgene rescued these cells. The cGMP-PDE6 activity of dark-adapted H258N mice showed an approximate three-fold increase in the rate of retinal cGMP hydrolysis: from 130.1 nmol x min(-1) x nmol(-1) rhodopsin in wild-type controls to 319.2 nmol x min(-1) x nmol(-1) rhodopsin in mutants, consistent with the hypothesis that inhibition of the PDE6beta activity by the regulatory PDE6gamma subunit is blocked by this mutation. In the albino (B6CBA x FVB) F2 hybrid background, electroretinograms (ERG) from H258N mice were similar to those obtained from affected Rambusch family members, as well as humans with the most common form of CSNB (X-linked), demonstrating a selective loss of the b-wave with relatively normal a-waves. When the H258N allele was introduced into the DBA background, there was no evidence of selective reduction in b-wave amplitudes; rather a- and b-wave amplitudes were both reduced. Thus, factors other than the PDE6B mutation itself could contribute to the variance of an electrophysiological response. Therefore, caution is advisable when interpreting physiological phenotypes associated with the same allele on different genetic backgrounds. Nevertheless, such animals should be of considerable value in further studies of the molecular pathology of CSNB.

}, keywords = {Adult, Animals, Cyclic Nucleotide Phosphodiesterases, Type 6, Disease Models, Animal, DNA Mutational Analysis, Electroretinography, Female, Humans, Male, Mice, Mice, Inbred DBA, Mice, Transgenic, Mutation, Night Blindness, Phosphoric Diester Hydrolases, Retinal Degeneration, Transgenes}, author = {Tsang, Stephen H and Woodruff, Michael L and Jun, Lin and Mahajan, Vinit and Yamashita, Clyde K and Pedersen, Robert and Lin, Chyuan-Sheng and Goff, Stephen P and Rosenberg, Thomas and Larsen, Michael and Farber, Debora B and Nusinowitz, Steven} }