Renal coloboma syndrome/dominant optic atrophy with severe retinal atrophy and de novo digenic mutations in PAX2 and OPA1.

Renal coloboma syndrome (RCS) and dominant optic atrophy are mainly caused by heterozygous mutations in PAX2 and OPA1, respectively. We describe a patient with digenic mutations in PAX2 and OPA1. A female infant was born without perinatal abnormalities. Magnetic resonance imaging at 4 months of age showed bilateral microphthalmia and optic nerve hypoplasia. Appropriate body size was present at 2 years of age, and mental development was favorable. Color fundus photography revealed severe retinal atrophy in both eyes. Electroretinography showed slight responses in the right eye, but no responses in the left eye, suggesting a high risk of blindness. Urinalysis results were normal, creatinine-based estimated glomerular filtration rate was 63.5 mL/min/1.73 m2, and ultrasonography showed bilateral hypoplastic kidneys. Whole exome sequencing revealed de novo frameshift mutations in PAX2 and OPA1. Both variants were classified as pathogenic (PVS1, PS2, PM2) based on the guidelines from the American College of Medical Genetics and Genomics (ACMG). Genetic testing for ocular diseases should be considered for patients with suspected RCS and a high risk of total blindness.

Sectorial Ganglion Cell Complex Thickness as Biomarker of Vision Outcome in Patients With Dominant Optic Atrophy.

Purpose: Dominant optic atrophy (DOA) is an inherited condition caused by autosomal dominant mutations involving the OPA-1 gene. The aim of this study was to assess the relationship between macular ganglion cell and inner plexiform layer (GC-IPL) thickness obtained from structural optical coherence tomography (OCT) and visual outcomes in DOA patients. Methods: The study recruited 33 patients with confirmed OPA-1 heterozygous mutation and DOA. OCT scans were conducted to measure the GC-IPL thickness. The average and sectorial Early Treatment Diabetic Retinopathy Study (ETDRS) charts (six-sector macular analysis to enhance the topographical analysis) centered on the fovea were considered. Several regression analyses were carried out to investigate the associations between OCT metrics and final best-corrected visual acuity (BCVA) as the dependent variable. Results: The mean BCVA was 0.43 ± 0.37 logMAR, and the average macular GC-IPL thickness was 43.65 ± 12.56 µm. All of the GC-IPL sectors were significantly reduced and correlated with BCVA. The univariate linear regression and the multivariate stepwise regression modeling showed that the strongest association with final BCVA was observed with the internal superior GC-IPL thickness. Dividing patients based on BCVA, we found a specific pattern. Specifically, in patients with BCVA ≤ 0.3 logMAR, the external superior and inferior sectors together with the internal superior were more significant; whereas, for BCVA > 0.3 logMAR, the external superior sector and internal superior sector were more significant. Conclusions: The study identified OCT biomarkers associated with visual outcomes in DOA patients. Moreover, we assessed a specific OCT biomarker for DOA progression, ranging from patients in the early stages of disease with more preserved GC-IPL sectorial thickness to advanced stages with severe thinning.

AFG3L2 and ACO2-Linked Dominant Optic Atrophy: Genotype-Phenotype Characterization Compared to OPA1 Patients.

PURPOSE: Heterozygous mutations in the AFG3L2 gene (encoding a mitochondrial protease indirectly reflecting on OPA1 cleavage) and ACO2 gene (encoding the mitochondrial enzyme aconitase) are associated with isolated forms of Dominant Optic Atrophy (DOA). We aimed at describing their neuro-ophthalmological phenotype as compared with classic OPA1-related DOA. DESIGN: Cross-sectional study. METHODS: The following neuro-ophthalmological parameters were collected: logMAR visual acuity (VA), color vision, mean deviation and foveal threshold at visual fields, average and sectorial retinal nerve fiber layer (RNFL), and ganglion cell layer (GCL) thickness on optical coherence tomography. ACO2 and AFG3L2 patients were compared with an age- and sex-matched group of OPA1 patients with a 1:2 ratio. All eyes were analyzed using a clustered Wilcoxon rank sum test with the Rosner-Glynn-Lee method. RESULTS: A total of 44 eyes from 23 ACO2 patients and 26 eyes from 13 AFG3L2 patients were compared with 143 eyes from 72 OPA1 patients. All cases presented with bilateral temporal-predominant optic atrophy with various degree of visual impairment. Comparison between AFG3L2 and OPA1 failed to reveal any significant difference. ACO2 patients compared to both AFG3L2 and OPA1 presented overall higher values of nasal RNFL thickness (P = .029, P = .023), average thickness (P = .012, P = .0007), and sectorial GCL thickness. These results were confirmed also comparing separately affected and subclinical patients. CONCLUSIONS: Clinically, DOA remains a fairly homogeneous entity despite the growing genetic heterogeneity. ACO2 seems to be associated with an overall better preservation of retinal ganglion cells, probably depending on the different pathogenic mechanism involving mtDNA maintenance, as opposed to AFG3L2, which is involved in OPA1 processing and is virtually indistinguishable from classic OPA1-DOA.

Peripapillary capillary network in dominant optic atrophy linked to OPA1 gene.

Peripapillary capillary network using optical coherence tomography angiography (OCT-A) was analysed in two siblings suffering from dominant optic atrophy linked to OPA-1 gene mutation. Peripapillary capillary network has been scarcely described in this type of optic atrophy.

Understanding the molecular basis and pathogenesis of hereditary optic neuropathies: towards improved diagnosis and management.

Hereditary optic neuropathies result from defects in the human genome, both nuclear and mitochondrial. The two main and most recognised phenotypes are dominant optic atrophy and Leber hereditary optic neuropathy. Advances in modern molecular diagnosis have expanded our knowledge of genotypes and phenotypes of inherited disorders that affect the optic nerve, either alone or in combination, with various forms of neurological and systemic degeneration. A unifying feature in the pathophysiology of these disorders appears to involve mitochondrial dysfunction, suggesting that the retinal ganglion cells and their axons are especially susceptible to perturbations in mitochondrial homoeostasis. As we better understand the pathogenesis behind these genetic diseases, aetiologically targeted therapies are emerging and entering into clinical trials, including treatments aimed at halting the cascade of neurodegeneration, replacing or editing the defective genes or their protein products, and potentially regenerating damaged optic nerves, as well as preventing generational disease transmission.

The Pattern of Retinal Ganglion Cell Loss in Wolfram Syndrome is Distinct From Mitochondrial Optic Neuropathies.

PURPOSE: To describe the clinical phenotype of a cohort of patients with Wolfram syndrome (WS), focusing on the pattern of optic atrophy correlated with brain magnetic resonance imaging (MRI) measurements, as compared with patients with OPA1-related dominant optic atrophy (DOA). DESIGN: Retrospective, comparative cohort study. METHODS: We reviewed 25 patients with WS and 33 age-matched patients affected by OPA1-related DOA. Ophthalmologic, neurologic, endocrinologic, and MRI data from patients with WS were retrospectively retrieved. Ophthalmologic data were compared with data from patients with OPA1-related DOA and further analyzed for age dependency dividing patients in age quartiles. In a subgroup of patients with WS, we correlated the structural damage assessed by optical coherence tomography (OCT) with brain MRI morphologic measurements. Visual acuity (VA), visual field mean defect (MD), retinal nerve fiber layer (RNFL), and ganglion cell layer (GCL) thickness were assessed by OCT and MRI morphologic measurements of anterior and posterior visual pathways. RESULTS: Optic atrophy was present in 100% of patients with WS. VA, MD, and RNFL thickness loss were worse in patients with WS with a faster decline since early age as compared with patients with DOA, who displayed a more stable visual function over the years. Conversely, GCL sectors were overall thinner in patients with DOA since early age compared to patients with WS, in which GCL thickness started to decline later in life. The neuroradiologic subanalysis on 11 patients with WS exhibited bilateral thinning of the anterior optic pathway, especially the prechiasmatic optic nerves and optic tracts. Optic tract thinning was significantly correlated with GCL thickness but not with RNFL parameters. CONCLUSIONS: Our results showed a generally more severe and diffuse degeneration of both anterior and posterior visual pathways in patients with WS, with fast deterioration of visual function and structural OCT parameters since early age. The pattern observed with OCT suggests that retinal ganglion cell axonal degeneration (ie, RNFL) precedes cellular body atrophy (ie, GCL) by about a decade. This differs substantially from DOA, in which a more stable visual function is evident with predominant early loss of GCL, indirectly supporting the lack of a primary mitochondrial dysfunction in patients with WS.

Prevalence of Macular Microcystoid Lacunae in Autosomal Dominant Optic Atrophy Assessed With Adaptive Optics.

BACKGROUND: To assess the prevalence of macular microcystoid lacunae in patients with autosomal dominant optic atrophy (ADOA) and its association with visual function and inner retinal morphology. METHODS: The study included 140 participants with ADOA, with a mean age of 44 (SD ±19, range 7-82) years. Study participants with a genetically verified sequence variant in the OPA1 gene were examined with best-corrected visual acuity, contrast sensitivity, optical coherence tomography (Spectralis, Heidelberg) and adaptive optics fundus photography (rtx1, Imagine Eyes). Optically empty microcystoid spaces in the ganglion cell layer and inner plexiform layer were mapped by inspection of the 2 sets of images. Data were analyzed with a mixed model adjusted for age and sex with family and individual as random effect. RESULTS: Microcystoid lacunae were present in 32 of 140 participants (23%) including 18 males and 14 females. Microcystoid lacunae were associated with younger age ( P = 0.0503) and a smaller nerve fiber layer volume ( P = 0.035). No association was found between presence of microcystoid lacunae and visual acuity ( P = 0.2), contrast sensitivity ( P = 0.8), axial length ( P = 0.7), or ganglion cell layer volume ( P = 0.2). The analysis showed moderately reduced visual acuity in patients with microcystoid lacunae. Normal and severely impaired visual function were seen only in participants without microcystoid lacunae. CONCLUSION: In ADOA, macular microcystoid lacunae were found in 23% of the study participants and tended to be present in younger participants with moderate visual acuity reduction and a smaller nerve fiber layer volume. Further studies are needed to investigate whether cavities left by dead ganglion cells are predictors of decrease in visual function.

Vision-related quality of life and visual ability in patients with autosomal dominant optic atrophy.

PURPOSE: The purpose of the study was to evaluate vision-related quality of life and visual ability in patients with OPA1 autosomal dominant optic atrophy (ADOA). METHODS: This cross-sectional, observational study included 145 participants with a mutation in the OPA1 gene associated with ADOA, 63 mutation-free first-degree relatives and 92 healthy subjects unrelated to the families. Participants underwent a clinical eye examination, and adult participants completed the National Eye Institute Visual Function Questionnaire (NEI-VFQ-39), while children completed the Cardiff Visual Ability Questionnaire for Children (CVAQC). RESULTS: In adults with ADOA, both mean visual acuity (VA) and mean contrast sensitivity (CS) were significantly inferior to both first-degree relatives and unrelated controls (p < 0.001). In children with ADOA, mean VA was significantly lower compared with first-degree relatives (p = 0.0052), whereas CS was not (0.127). Adults with ADOA scored lower than both comparator groups on composite score (p < 0.001), general health subscale (p = 0.0075) and all vision-related subscales (p < 0.001) except the ocular pain subscale (p = 0.2). In children with ADOA, the median CVAQC logit score was significantly lower compared with first-degree relatives (p = 0.037). The science lessons subscale was significantly lower for children with ADOA compared with first-degree relatives (p = 0.046), as well as the language lessons subscale (p = 0.038). For adults, composite score and subscale scores were significantly associated with both VA, CS and fixation status. CONCLUSION: OPA1 mutation is associated with lower quality of life and visual ability in patients with ADOA compared with both first-degree relatives and unrelated controls. VA, CS and fixation status affect quality of life in patients with ADOA.

Optical coherence tomography angiography in the multimodal assessment of the retinal posterior pole in autosomal dominant optic atrophy.

PURPOSE: To assess retinal vascular involvement in patients with autosomal dominant optic atrophy (ADOA) genetically confirmed by the presence of the OPA1 (Optic Atrophy 1) gene mutation using a multimodal protocol of investigation of retinal posterior pole. METHODS: In this cross-sectional, case-control, observational study, both eyes of 13 patients with a genetic diagnosis of ADOA were compared with both eyes of 13 healthy controls (HCs). All subjects underwent full ophthalmological examination, spectral domain-optical coherence tomography (SD-OCT), fundus perimetry (FP) and OCT angiography (OCTA). RESULTS: Vessel density (VD) of the superficial and deep macular vascular plexi and of the radial peripapillary capillary plexus were significantly decreased (p ≤ 0.001) in ADOA patients compared with HCs. The area under the receiver operating characteristics analysis also revealed high values of sensitivity and specificity of OCTA parameters in distinguish between patients and HCs. A strong correlation (Pearson Coefficient, r = 0.91) emerged between OCTA VD of the superficial retinal plexus and the average Ganglion Cell Layer (GCL) thickness as measured by SD-OCT; a slightly lower correlation (Pearson Coefficient, r = 0.89) was also found between VD of the deep plexus and the average GCL thickness of the same eyes in patients with ADOA. The correlation among values of differential light sensitivity (DLS) measured by FP with VD and GCL thickness parameters was also investigated. The correlation analysis among DLS and the VD parameters showed from low-to-moderate correlation (ranging from r = 0.29 for the deep fovea VD to r = 0.59 for the deep whole image VD). The correlation coefficient between the mean DLS and the average thickness of GCL was more significant (Pearson Coefficient, r = 0.75). A significant correlation emerged also between the VD and the visual acuity, in terms of LogMAR BCVA (best-corrected visual acuity), especially for the VD of the deep capillary plexus (Pearson Coefficient for the Deep whole Image VD and LogMAR BCVA r = -0.75; for the Deep parafovea VD and LogMAR BCVA r = -0.78). CONCLUSION: Retinal microvascular assessment by OCTA angiography can provide relevant clinical information on retinal involvement in ADOA patients. In patients with genetically confirmed OPA1-related ADOA, there is a decrease in retinal vessel density associated with GCL thinning and DLS reduction.

Induced Pluripotent Stem Cells for Inherited Optic Neuropathies-Disease Modeling and Therapeutic Development.

BACKGROUND: Inherited optic neuropathies (IONs) cause progressive irreversible visual loss in children and young adults. There are limited disease-modifying treatments, and most patients progress to become severely visually impaired, fulfilling the legal criteria for blind registration. The seminal discovery of the technique for reprogramming somatic nondividing cells into induced pluripotent stem cells (iPSCs) has opened several exciting opportunities in the field of ION research and treatment. EVIDENCE ACQUISITION: A systematic review of the literature was conducted with PubMed using the following search terms: autosomal dominant optic atrophy, ADOA, dominant optic atrophy, DOA, Leber hereditary optic neuropathy, LHON, optic atrophy, induced pluripotent stem cell, iPSC, iPSC derived, iPS, stem cell, retinal ganglion cell, and RGC. Clinical trials were identified on the ClinicalTrials.gov website. RESULTS: This review article is focused on disease modeling and the therapeutic strategies being explored with iPSC technologies for the 2 most common IONs, namely, dominant optic atrophy and Leber hereditary optic neuropathy. The rationale and translational advances for cell-based and gene-based therapies are explored, as well as opportunities for neuroprotection and drug screening. CONCLUSIONS: iPSCs offer an elegant, patient-focused solution to the investigation of the genetic defects and disease mechanisms underpinning IONs. Furthermore, this group of disorders is uniquely amenable to both the disease modeling capability and the therapeutic potential that iPSCs offer. This fast-moving area will remain at the forefront of both basic and translational ION research in the coming years, with the potential to accelerate the development of effective therapies for patients affected with these blinding diseases.

Genetic Spectrum and Characteristics of Hereditary Optic Neuropathy in Taiwan.

Hereditary optic neuropathy (HON) is a group of genetically heterogeneous diseases that cause optic nerve atrophy and lead to substantial visual impairment. HON may present with optic nerve atrophy only or in association with various systemic abnormalities. Although a genetic survey is indispensable for diagnosing HON, conventional sequencing techniques could render its diagnosis challenging. In this study, we attempted to explore the genetic background of patients with HON in Taiwan through capture-based next-generation sequencing targeting 52 HON-related genes. In total, 57 patients from 48 families were recruited, with 6 patients diagnosed as having Leber hereditary optic neuropathy through initial screening for three common variants (m.3460G>A, m.11778G>A, m.14484T>C). Disease-causing genotypes were identified in 14 (33.3%) probands, and OPA1 variants were the most prevalent cause of autosomal HON. Exposure to medications such as ethambutol could trigger an attack of autosomal dominant optic atrophy. WFS1 variants were identified in three probands with variable clinical features in our cohort. Hearing impairment could occur in patients with OPA1 or WFS1 variants. This is the first comprehensive study investigating the genetic characteristics of HON in Taiwan, especially for autosomal HON. Our results could provide useful information for clinical diagnosis and genetic counseling in this field.

First submicroscopic inversion of the OPA1 gene identified in dominant optic atrophy - a case report.

BACKGROUND: Dominant optic atrophy (DOA) is an inherited optic neuropathy that mainly affects visual acuity, central visual fields and color vision due to a progressive loss of retinal ganglion cells and their axons that form the optic nerve. Approximately 45-90% of affected individuals with DOA harbor pathogenic variants in the OPA1 gene. The mutation spectrum of OPA1 comprises nonsense, canonical and non-canonical splice site, frameshift and missense as well as copy number variants, but intragenic inversions have not been reported so far. CASE PRESENTATION: We report a 33-year-old male with characteristic clinical features of DOA. Whole-genome sequencing identified a structural variant of 2.4 kb comprising an inversion of 937 bp at the OPA1 locus. Fine mapping of the breakpoints to single nucleotide level revealed that the structural variation was an inversion flanked by two deletions. As this rearrangement inverts the entire first exon of OPA1, it was classified as likely pathogenic. CONCLUSIONS: We report the first DOA case harboring an inversion in the OPA1 gene. Our study demonstrates that copy-neutral genomic rearrangements have to be considered as a possible cause of disease in DOA cases.

Peripapillary and macular morpho-vascular changes in patients with genetic or clinical diagnosis of autosomal dominant optic atrophy: a case-control study.

PURPOSE: To evaluate the macular and peripapillary morpho-vascular changes in ADOA, using optical coherence tomography (OCT) and OCT angiography (OCTA). METHODS: Prospectively defined, cross-sectional case-control study. Consecutive patients with a genetic or clinical diagnosis of ADOA along with age- and sex-matched controls were included. The radial peripapillary capillary (RPC) density and vessel density (VD) in the parafoveal superficial and deep capillary plexuses (SCP and DCP, respectively) were evaluated with OCTA. The ganglion cell complex (GCC) and retinal nerve fiber layer (RNFL) thickness were determined using structural OCT. We applied a previously validated customized macro (Fiji, SciJava Consortium) to compute RPC density. The remaining parameters were calculated by the built-in software. Non-parametric methods were used for data analysis. The target α level was 0.05, which was adjusted through Bonferroni's correction when multiple outcomes were tested. RESULTS: Fifty-eight eyes (n = 29 control; n = 29 ADOA) from 30 subjects (mean age 42.43 ± 15.30 years; 37.93% male) were included. Parafoveal SCP VD, GCC thickness, RPC VD in the temporal quadrant, as well as RNFL thickness in the nasal and temporal quadrants were decreased in ADOA eyes (all p < 0.001). When only patients with genetically confirmed diagnosis were included, capillary dropout in the circumpapillary superior and inferior quadrants also became evident (both p < 0.001). The GCC/parafoveal SCP ratio was increased in ADOA, relatively to matched controls. In contrast, none of the circumpapillary morpho-vascular ratios was significantly different in ADOA eyes. CONCLUSIONS: The microvascular and structural changes found in ADOA suggest that both the macular and peripapillary regions are involved, although the threshold for damage of the structural and vascular components may be different for each region. Larger series with longitudinal follow-up may validate OCTA biomarkers helpful for disease monitoring.

Optical Coherence Tomography of the Retinal Ganglion Cell Complex in Leber's Hereditary Optic Neuropathy and Dominant Optic Atrophy.

Background: Mitochondrial optic neuropathies such as Leber's Hereditary Optic Neuropathy (LHON) and Dominant Optic Atrophy (DOA) have been shown to produce an optic neuropathy secondary to retinal ganglion cell loss with thinning of the retinal ganglion cell complex (RGCC). Methods: We performed a retrospective analysis assessing the thicknesses of the peripapillary retinal nerve fiber layer (pRNFL) along with the macular retinal ganglion cell-inner plexiform layer (RGC-IPL) using optical coherence tomography (OCT). We compared these changes among acute and chronic LHON, DOA, and normal healthy control patients. Results: Patients with chronic LHON exhibited statistically significant thinning of the RNFL in the superior, nasal, and inferior quadrants of the retina. In acute LHON, the RNFL was relatively thicker in all but the temporal quadrant when compared with respective quadrants in normal eyes; however, statistical significance was not achieved. In DOA, the RNFL was thinnest in the superior and inferior quadrants of the retina, measuring between acute and chronic LHON thickness values. In chronic LHON and DOA, both the pRNFL and RGC-IPL were significantly thinner in all four retinal quadrants relative to controls. Conclusions: This article represents the first comparative study of the RGCC between LHON and DOA. Our findings demonstrated significant thickness reductions in pRNFL and macular RGC-IPL in patients with LHON and DOA, with different specific patterns consistent with the general patterns of thinning classically observed. This study suggests the usefulness of the RGCC as a potential in vivo biomarker for assessing disease in patients with LHON and DOA.

[Genetic Causes and Genetic Diagnostic Testing of Inherited Optic Atrophies]. / Genetische Ursachen und genetische Diagnostik bei hereditären Optikusatrophien.

Hereditary optic atrophies are a heterogeneous group of rare degenerative disease affecting the retinal ganglion cells and their axons which form the optic nerve. With an estimated prevalence of 1 : 10 000 to 1 : 20 000, hereditary optic atrophies in their entirety affect about 4000 to 8000 people in Germany. The most common forms are Leber's hereditary optic atrophy (LHON) and autosomal dominant optic atrophy (ADOA). Besides the common forms of isolated optic atrophies which exclusively affect the visual system, there are a variety of conditions in which the optic atrophy is part of a syndromic disease with additional symptoms that are mostly neurosensory, neurological or neuromuscular. The mode of inheritance is heterogeneous with LHON showing maternal inheritance and an autosomal dominant inheritance in families with ADOA. There are rarer cases of optic atrophy following an autosomal recessive or X-linked recessive mode of inheritance. The penetrance is incomplete. Moreover, in LHON, there are many more males than females who develop the disease. The genetic causes of hereditary optic atrophies are complex in terms of the diversity of the involved genes. However, most of these causes are already known. Therefore, molecular genetic diagnostic testing yields a meaningful result in the majority of tested subjects and enables confirmation of the suspected clinical diagnosis, reliable counseling of the families with respect to the genetic risk, and - in subjects with genetically confirmed LHON - initiation of therapeutic intervention. This article provides an overview of current knowledge of the genetic causes of hereditary optic neuropathies, and the options and modalities of molecular genetic diagnostic testing, including practical guidelines.