A Retrospective Longitudinal Study of 460 Patients with ABCA4-Associated Retinal Disease.

PURPOSE: To investigate the distribution of genotypes and natural history of ABCA4-associated retinal disease in a large cohort of patients seen at a single institution. DESIGN: Retrospective, single-institution cohort review. PARTICIPANTS: Patients seen at the University of Iowa between November 1986 and August 2022 clinically suspected to have disease caused by sequence variations in ABCA4. METHODS: DNA samples from participants were subjected to a tiered testing strategy progressing from allele-specific screening to whole genome sequencing. Charts were reviewed, and clinical data were tabulated. The pathogenic severity of the most common alleles was estimated by studying groups of patients who shared 1 allele. Groups of patients with shared genotypes were reviewed for evidence of modifying factor effects. MAIN OUTCOME MEASURES: Age at first uncorrectable vision loss, best-corrected visual acuity, and the area of the I2e isopter of the Goldmann visual field. RESULTS: A total of 460 patients from 390 families demonstrated convincing clinical features of ABCA4-associated retinal disease. Complete genotypes were identified in 399 patients, and partial genotypes were identified in 61. The median age at first vision loss was 16 years (range, 4-76 years). Two hundred sixty-five families (68%) harbored a unique genotype, and no more than 10 patients shared any single genotype. Review of the patients with shared genotypes revealed evidence of modifying factors that in several cases resulted in a > 15-year difference in age at first vision loss. Two hundred forty-one different alleles were identified among the members of this cohort, and 161 of these (67%) were found in only a single individual. CONCLUSIONS: ABCA4-associated retinal disease ranges from a very severe photoreceptor disease with an onset before 5 years of age to a late-onset retinal pigment epithelium-based condition resembling pattern dystrophy. Modifying factors frequently impact the ABCA4 disease phenotype to a degree that is similar in magnitude to the detectable ABCA4 alleles themselves. It is likely that most patients in any cohort will harbor a unique genotype. The latter observations taken together suggest that patients' clinical findings in most cases will be more useful for predicting their clinical course than their genotype. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Propensity of Patient-Derived iPSCs for Retinal Differentiation: Implications for Autologous Cell Replacement.

Prior to use, newly generated induced pluripotent stem cells (iPSC) should be thoroughly validated. While excellent validation and release testing assays designed to evaluate potency, genetic integrity, and sterility exist, they do not have the ability to predict cell type-specific differentiation capacity. Selection of iPSC lines that have limited capacity to produce high-quality transplantable cells, places significant strain on valuable clinical manufacturing resources. The purpose of this study was to determine the degree and root cause of variability in retinal differentiation capacity between cGMP-derived patient iPSC lines. In turn, our goal was to develop a release testing assay that could be used to augment the widely used ScoreCard panel. IPSCs were generated from 15 patients (14-76 years old), differentiated into retinal organoids, and scored based on their retinal differentiation capacity. Despite significant differences in retinal differentiation propensity, RNA-sequencing revealed remarkable similarity between patient-derived iPSC lines prior to differentiation. At 7 days of differentiation, significant differences in gene expression could be detected. Ingenuity pathway analysis revealed perturbations in pathways associated with pluripotency and early cell fate commitment. For example, good and poor producers had noticeably different expressions of OCT4 and SOX2 effector genes. QPCR assays targeting genes identified via RNA sequencing were developed and validated in a masked fashion using iPSCs from 8 independent patients. A subset of 14 genes, which include the retinal cell fate markers RAX, LHX2, VSX2, and SIX6 (all elevated in the good producers), were found to be predictive of retinal differentiation propensity.

Scleral pits represent degeneration around the posterior ciliary arteries and are signs of disease severity in choroideremia.

BACKGROUND: Choroideremia is an X-linked recessive condition characterized by progressive chorioretinal degeneration. Recently, peculiar scleral ectasias, termed scleral "pits" and "tunnels," have been described as a novel finding in patients with choroideremia, but little is known regarding their etiology or their evolution over time. SUBJECTS: This is a retrospective chart review of consecutive patients with molecularly-confirmed choroideremia and related female carriers seen at a university-based tertiary referral center from January 2010 to July 2016. Multimodal imaging was evaluated for the evolution of scleral pits on fundus photography and scleral tunnels on optical coherence tomography (OCT). The presence of scleral pits and tunnels was correlated with markers of disease severity including age, visual acuity, and severity of visual field loss. RESULTS: Thirty patients (21 affected males, 9 female carriers) were included in the study. Scleral pits were seen in 38.1% (8/21) of affected males and found to occur at insertion sites of the posterior ciliary arteries. Those with scleral pits were older, had poorer visual acuity, and more severe visual field loss than those without (p ≤ 0.05). Scleral tunnels were common (68.4%, 13/19 affected males with available OCT imaging), but no statistically-significant associations with disease severity were seen. The development of new scleral pits and tunnels was observed on longitudinal imaging in 4 and 2 affected males, respectively. No scleral pits or tunnels were visualized in any female carriers. CONCLUSIONS: Scleral pits represent degeneration around the posterior ciliary arteries and may be useful as clinical markers of disease severity in choroideremia.

Wide-Field Swept-Source OCT and Angiography in X-Linked Retinoschisis.

PURPOSE: Retinal vascular and structural changes, particularly outside of the central macula, are not well characterized in X-linked retinoschisis (XLRS). We aim to describe wide-field swept-source OCT (SS-OCT) and swept-source OCT angiography (SS-OCTA) findings in XLRS. DESIGN: Retrospective, cross-sectional study at a tertiary referral center. PARTICIPANTS: Nine consecutive male patients with molecularly confirmed XLRS. METHODS: All patients underwent complete ophthalmic examination with multimodal imaging, including SS-OCT with SS-OCTA (PLEX Elite 9000; Carl-Zeiss Meditec Inc., Dublin, CA). Images were then reviewed by 2 retinal specialists as independent graders to determine the frequency and distribution of retinal structural and vascular abnormalities. MAIN OUTCOME MEASURES: Structural and vascular abnormalities seen on SS-OCT and SS-OCTA in patients with XLRS, with attention to the retinal layers involved, the regional distribution of schitic spaces in the posterior pole, and vascular abnormalities within the superficial and deep capillary plexuses. RESULTS: Eighteen eyes from 9 male patients (mean age, 20 years; range 9-40) with molecularly confirmed XLRS were included. Median best-corrected visual acuity measured 20/63 (range, 20/25-10/300). A total of 17 of 18 eyes (94.4%) were noted to have schitic spaces on SS-OCT, and these were observed to be predominantly within the inner nuclear layer in all 17 eyes. A regional variation in the distribution of cysts was noted, with schitic spaces within the ganglion cell layer (13/17 eyes; 76.5%) observed to be perifoveal and those within the outer nuclear layer (8/17 eyes, 47.1%) observed to be mostly extramacular. All eyes had vascular abnormalities on SS-OCTA, including an irregular foveal avascular zone and flow loss within the deep capillary plexus corresponding to the distribution of the schisis. CONCLUSIONS: Wide-field SS-OCT and SS-OCTA provide detailed visualization of structural and vascular changes in XLRS and may be helpful for monitoring disease progression or treatment response in clinical trials for the disease.

CRISPR-Cas9-Mediated Correction of the 1.02 kb Common Deletion in CLN3 in Induced Pluripotent Stem Cells from Patients with Batten Disease.

Juvenile neuronal ceroid lipofuscinosis (Batten disease) is a rare progressive neurodegenerative disorder caused by mutations in CLN3. Patients present with early-onset retinal degeneration, followed by epilepsy, progressive motor deficits, cognitive decline, and premature death. Approximately 85% of individuals with Batten disease harbor at least one allele containing a 1.02 kb genomic deletion spanning exons 7 and 8. This study demonstrates CRISPR-Cas9-based homology-dependent repair of this mutation in induced pluripotent stem cells generated from two independent patients: one homozygous and one compound heterozygous for the 1.02 kb deletion. Our strategy included delivery of a construct that carried >3 kb of DNA: wild-type CLN3 sequence and a LoxP-flanked, puromycin resistance cassette for positive selection. This strategy resulted in correction at the genomic DNA and mRNA levels in the two independent patient lines. These CRISPR-corrected isogenic cell lines will be a valuable tool for disease modeling and autologous retinal cell replacement.

Patient-specific induced pluripotent stem cells to evaluate the pathophysiology of TRNT1-associated Retinitis pigmentosa.

Retinitis pigmentosa (RP) is a heterogeneous group of monogenic disorders characterized by progressive death of the light-sensing photoreceptor cells of the outer neural retina. We recently identified novel hypomorphic mutations in the tRNA Nucleotidyl Transferase, CCA-Adding 1 (TRNT1) gene that cause early-onset RP. To model this disease in vitro, we generated patient-specific iPSCs and iPSC-derived retinal organoids from dermal fibroblasts of patients with molecularly confirmed TRNT1-associated RP. Pluripotency was confirmed using rt-PCR, immunocytochemistry, and a TaqMan Scorecard Assay. Mutations in TRNT1 caused reduced levels of full-length TRNT1 protein and expression of a truncated smaller protein in both patient-specific iPSCs and iPSC-derived retinal organoids. Patient-specific iPSCs and iPSC-derived retinal organoids exhibited a deficit in autophagy, as evidenced by aberrant accumulation of LC3-II and elevated levels of oxidative stress. Autologous stem cell-based disease modeling will provide a platform for testing multiple avenues of treatment in patients suffering from TRNT1-associated RP.

Calpain-5 mutations cause autoimmune uveitis, retinal neovascularization, and photoreceptor degeneration.

Autosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV) is an autoimmune condition of the eye that sequentially mimics uveitis, retinitis pigmentosa, and proliferative diabetic retinopathy as it progresses to complete blindness. We identified two different missense mutations in the CAPN5 gene in three ADNIV kindreds. CAPN5 encodes calpain-5, a calcium-activated cysteine protease that is expressed in retinal photoreceptor cells. Both mutations cause mislocalization from the cell membrane to the cytosol, and structural modeling reveals that both mutations lie within a calcium-sensitive domain near the active site. CAPN5 is only the second member of the large calpain gene family to cause a human Mendelian disorder, and this is the first report of a specific molecular cause for autoimmune eye disease. Further investigation of these mutations is likely to provide insight into the pathophysiologic mechanisms of common diseases ranging from autoimmune disorders to diabetic retinopathy.

Localization of complement 1 inhibitor (C1INH/SERPING1) in human eyes with age-related macular degeneration.

Age-related macular degeneration (AMD) is a common degenerative disease resulting in injury to the retina, retinal pigment epithelium and choriocapillaris. Recent data from histopathology, animal models and genetic studies have implicated altered regulation of the complement system as a major factor in the incidence and progression of this disease. A variant in the gene SERPING1, which encodes C1INH, an inhibitor of the classical and lectin pathways of complement activation, was recently shown to be associated with AMD. In this study we sought to determine the localization of C1INH in human donor eyes. Immunofluorescence studies using a monoclonal antibody directed against C1INH revealed localization to photoreceptor cells, inner nuclear layer neurons, choriocapillaris, and choroidal extracellular matrix. Drusen did not exhibit labeling. Genotype at rs2511989 did not appear to affect C1INH abundance or localization, nor was it associated with significant molecular weight differences when evaluated by Western blot. In a small number of eyes (n = 7 AMD and n = 7 control) AMD affection status was correlated with increased abundance of choroidal C1INH. These results indicate that C1INH protein is present in the retina and choroid, where it may regulate complement activation.