Leber's Hereditary Optic Neuropathy Research Articles

Galactose-Replacement Unmasks the Biochemical Consequences of the G11778A Mitochondrial DNA Mutation of LHON in Patient-Derived Fibroblasts.

Leber's hereditary optic neuropathy (LHON) is a visual impairment associated with mutations of mitochondrial genes encoding elements of the electron transport chain. While much is known about the genetics of LHON, the cellular pathophysiology leading to retinal ganglion cell degeneration and subsequent vision loss is poorly understood. The impacts of the G11778A mutation of LHON on bioenergetics, redox balance and cell proliferation were examined in patient-derived fibroblasts. Replacement of glucose with galactose in the culture media reveals a deficit in the proliferation of G11778A fibroblasts, imparts a reduction in ATP biosynthesis, and a reduction in capacity to accommodate exogenous oxidative stress. While steady-state ROS levels were unaffected by the LHON mutation, cell survival was diminished in response to exogenous H2O2.

Abstract P23: Mitochondrial Delivery of Functional Nucleic Acids for Targeting of Mitochondrial Dysfunction

Abstract Mitochondria is the main power supply for cellular activity and a key player for the regulation of cellular metabolism, and they contain their own DNA. Critical proteins for mitochondrial functions are not only encoded by nuclear DNA (nDNA) but also by mitochondrial DNA (mtDNA). Abnormalities in mitochondrial functions could lead to diseases including neurodegeneration, diabetes, and cancer progression. The ability for a non-coding RNA (β2.7) of human cytomegalovirus (CMV) to localize to the host mitochondria revealed its potential to be used as a tool for mitochondria gene targeting. Using computational methods, our lab identified four thermodynamically conserved structural subdomains (D1 to D4) within the β2.7 RNA. While all four domains exhibited mitochondrial uptake potential, sub-domain D3 exhibited the highest absolute mitochondrial targeting activity and sub-domain D2 the highest activity per nucleotide. Further modifications on different sub-domain alignments found that maximum uptake efficiency was achieved by tandem repeats of 4 copies of D3 domains followed by 4 copies of D2 domains (abbreviated as D3 × 4_D2 × 4). Delivery of a GFP-coding mRNA or antisense RNA targeting mitochondrial genes mt-ATP6 and mt-ATP8 both confirmed its ability to co-deliver functional RNA into mitochondria. To cleave and destroy mutated mitochondrial genomes for future gene therapeutic applications, we explore mitochondrial delivery of the CRISPR-Cas9 system. The mRNAs coding for the wild-type Cas9 as well as more specific Cas9 variants were fused to the mitochondrial delivery vector (D3 × 4_D2 × 4). Latest RT-qPCR on mitochondrial RNA showed delivery of Cas9 mRNA into mitochondria of HepG2 cells. Currently, we investigate co-delivery of single-guide RNA and quantify Cas9 expression in mitochondria. In an alternative approach we deliver sequences coding for functional mitochondrial protein. Examples are the mRNAs coding for mitochondrial proteins mt-ND1, -ND4 or -ND6 which are frequently mutated is patients with Leber’s hereditary optic neuropathy (LHON). Citation Format: Jinglin Ruan, Volker Patzel. Mitochondrial Delivery of Functional Nucleic Acids for Targeting of Mitochondrial Dysfunction [abstract]. In: Proceedings of Frontiers in Cancer Science; 2023 Nov 6-8; Singapore. Philadelphia (PA): AACR; Cancer Res 2024;84(8_Suppl):Abstract nr P23.

Assessing Clinically Relevant Recovery of Visual Acuity Over Time in Patients with Leber Hereditary Optic Neuropathy Treated with Idebenone: Results from the LEROS Study (S40.001)

Assessing Clinically Relevant Recovery of Visual Acuity Over Time in Patients with Leber Hereditary Optic Neuropathy Treated with Idebenone: Results from the LEROS Study (S40.001)

Leber Hereditary Optic Neuropathy Plus Phenotype With Double Point Mutations (m.11778 G>A and m.14484T>C) and Concurrent Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease (MOGAD).

Leber Hereditary Optic Neuropathy Plus Phenotype With Double Point Mutations (m.11778 G>A and m.14484T>C) and Concurrent Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease (MOGAD).

Identification and characterization of a new pathologic mutation in a large Leber hereditary optic neuropathy pedigree

BackgroundMost patients suffering from Leber hereditary optic neuropathy carry one of the three classic pathologic mutations, but not all individuals with these genetic alterations develop the disease. There are different risk factors that modify the penetrance of these mutations. The remaining patients carry one of a set of very rare genetic variants and, it appears that, some of the risk factors that modify the penetrance of the classical pathologic mutations may also affect the phenotype of these other rare mutations.ResultsWe describe a large family including 95 maternally related individuals, showing 30 patients with Leber hereditary optic neuropathy. The mutation responsible for the phenotype is a novel transition, m.3734A > G, in the mitochondrial gene encoding the ND1 subunit of respiratory complex I. Molecular-genetic, biochemical and cellular studies corroborate the pathogenicity of this genetic change.ConclusionsWith the study of this family, we confirm that, also for this very rare mutation, sex and age are important factors modifying penetrance. Moreover, this pedigree offers an excellent opportunity to search for other genetic or environmental factors that additionally contribute to modify penetrance.

Autosomal Recessive Leber Hereditary Optic Neuropathy Triggered by Superior Mesenteric Artery Syndrome.

Autosomal Recessive Leber Hereditary Optic Neuropathy Triggered by Superior Mesenteric Artery Syndrome.

Poor visual prognosis of Asian patients with 3460 mitochondrial DNA mutation in Leber's hereditary optic neuropathy

BackgroundAmong the 3 primary mutations of Leber's hereditary optic neuropathy (LHON), the incidence of LHON with a mutation at nucleotide position 3460 is the lowest in Asians. Therefore, information about the clinical manifestations of LHON mutations in Asians with the 3460 mutation is limited. ObjectiveTo determine the clinical manifestations including visual prognosis of Asians with the LHON 3460 mutation. MethodsWe performed a retrospective study of 5 Korean LHON patients with the 3460 mutation. ResultsAll patients were male, and the age of onset for visual impairment varied from 17 to 35 years, with an average of 25.4 ± 7.16 years. Among the 10 affected eyes, only 1 eye of 1 patient showed visual improvement to 20/50 at 2 years after onset. The remaining patients had a visual acuity of worse than 20/200. ConclusionThe visual prognosis of Korean patients with the LHON 3460 mutation was generally poor. Further studies regarding Asian patients with the LHON 3460 mutation are necessary.

Peripapillary hyperreflective ovoid mass-like structures: multimodal imaging and associated diseases.

Growing evidence has demonstrated that peripapillary hyperreflective ovoid mass-like structures (PHOMS) are novel structures rather than a subtype of optic disc drusen. They correspond to the laterally bulging herniation of optic nerve fibers and are believed to be the marker of axoplasmic stasis. PHOMS present in a broad spectrum of diseases, including optic disc drusen, tilted disc syndrome, papilloedema, multiple sclerosis, non-arteritic anterior ischemic optic neuropathy, optic neuritis, Leber hereditary optic neuropathy, and so on. We focus on the multimodal imaging features, pathophysiological mechanisms of PHOMS, and their association with multiple diseases and healthy people in this review to deepen the ophthalmologists' understanding of PHOMS. Additionally, we provide some new directions for future research.

Generation of iPSCs from identical twin, one affected by LHON and one unaffected, both carrying a combination of two mitochondrial variants: m.14484 T>C and m.10680G>A

Leber hereditary optic neuropathy (LHON) is one of the most common mitochondrial illness, causing retinal ganglion cell degeneration and central vision loss. It stems from point mutations in mitochondrial DNA (mtDNA), with key mutations being m.3460G > A, m.11778G > A, and m.14484 T > C. Fibroblasts from identical twins, sharing m.14484 T > C and m.10680G > A variants each with 70 % heteroplasmy, were used to generate iPSC lines. Remarkably, one twin, a LHON patient, displayed symptoms, while the other, a carrier, remained asymptomatic. These iPSCs offer a valuable tool for studying factors influencing disease penetrance and unravelling the role of m.10680G > A, which is still debated.

Digenic Leigh syndrome on the background of the m.11778G>A Leber hereditary optic neuropathy variant.

Leigh syndrome spectrum (LSS) is a primary mitochondrial disorder defined neuropathologically by a subacute necrotizing encephalomyelopathy and characterised by bilateral basal ganglia and/or brainstem lesions. LSS is associated with variants in several mitochondrial DNA (mtDNA) genes and more than 100 nuclear genes, most often related to mitochondrial complex I (CI) dysfunction. Rarely, LSS has been reported in association with primary Leber hereditary optic neuropathy (LHON) variants of the mtDNA, coding for CI subunits (m.3460G>A in MT-ND1, m.11778G>A in MT-ND4, and m.14484T>C in MT-ND6). The underlying mechanism by which these variants manifest as LSS, a severe neurodegenerative disease, as opposed to the LHON phenotype of isolated optic neuropathy, remains an open question. Here, we analyse the exome sequencing of six probands with LSS carrying primary LHON variants, and report digenic co-occurrence of the m.11778G>A variant with damaging heterozygous variants in nuclear disease genes encoding CI subunits as a plausible explanation. Our findings suggest a digenic mechanism of disease for m.11778G>A-associated LSS, consistent with recent reports of digenic disease in individuals manifesting with LSS due to biallelic variants in the recessive LHON-associated disease gene DNAJC30 in combination with heterozygous variants in CI subunits.

Mitochondrial DNA mutations in Korean patients with Leber’s hereditary optic neuropathy

In order to explore the spectrum of mitochondrial DNA (mtDNA) mutations in Korean patients with Leber's hereditary optic neuropathy (LHON), we investigated the spectrum of mtDNA mutations in 145 Korean probands confirmed with the diagnosis of LHON. Total genomic DNA was isolated from the peripheral blood leukocytes of the patients with suspected LHON, and mtDNA mutations were identified by direct sequencing. Analysis of mtDNA mutations revealed seven primary LHON mutations including the nucleotide positions (nps) 11778A (101 probands, 69.2%), 14484C (31 probands, 21.2%), 3460A (5 probands, 3.4%), and G3635A, G3733A, C4171A, and G13051A mutations in one proband each. In addition, two provisional mtDNA mutations at nps T3472C, and G13259A were each found in one proband, respectively. Another provisional mtDNA mutation at np T3394C was found in two probands. In conclusion, the spectrum of mtDNA mutations in Korean patients with LHON may differ from other ethnicities, which is characterized by high prevalence of 11778A and 14484C mutations, and a low prevalence of the 3460A mutation.

Electroretinographic oscillatory potentials in Leber hereditary optic neuropathy.

Leber hereditary optic neuropathy (LHON) affects retinal ganglion cells causing severe vision loss. Pattern electroretinogram and photopic negative response (PhNR) of the light-adapted (LA) full-field electroretinogram (ERG) are typically affected in LHON. In the present study, we evaluated dark-adapted (DA) and LA oscillatory potentials (OPs) of the flash ERG in genetically characterized LHON patients to dissociate slow from fast components of the response. Seven adult patients (mean age = 28.4 ± 5.6) in whom genetic diagnosis confirmed LHON with mtDNA or nuclear DNAJC30 (arLHON) pathogenic variants were compared to 12 healthy volunteers (mean age = 35.0 ± 12.1). Full-field ERGs were recorded from both eyes. Offline digital filters at 50, 75 and 100Hz low cutoff frequencies were applied to isolate high-frequency components from the original ERG signals. ERG a-waves and b-waves were comparable between LHON patients and controls, while PhNR was significantly reduced (p = 0.009) in LHON patients compared to controls, as expected. OPs derived from DA signals (75Hz low cutoff frequency) showed reduced peak amplitude for OP2 (p = 0.019). LA OP differences between LHON and controls became significant (OP2: p = 0.047, OP3: p = 0.039 and OP4: p = 0.013) when the 100Hz low-cutoff frequency filter was applied. Reduced OPs in LHON patients may represent disturbed neuronal interactions in the inner retina with preserved photoreceptoral (a-wave) to bipolar cell (b-wave) activation. Reduced DA OP2 and high-cutoff LA OP alterations may be further explored as functional measures to characterize LHON status and progression.

The Optic Nerve at Stake: Update on Environmental Factors Modulating Expression of Leber's Hereditary Optic Neuropathy.

Optic neuropathies are characterized by the degeneration of the optic nerves and represent a considerable individual and societal burden. Notably, Leber's hereditary optic neuropathy (LHON) is a devastating vision disease caused by mitochondrial gene mutations that hinder oxidative phosphorylation and increase oxidative stress, leading to the loss of retinal ganglion neurons and axons. Loss of vision is rapid and severe, predominantly in young adults. Penetrance is incomplete, and the time of onset is unpredictable. Recent findings revealed that the incidence of genetic LHON susceptibility is around 1 in 1000, much higher than believed till now. Environmental factors are critical in LHON triggering or severity. Families at risk have a very strong demand for how to prevent the onset or limit the severity of the disease. Here, we review recent knowledge of the extrinsic determinants of LHON expression, including lifestyle, dietary supplements, common chemicals, and drugs.

Development of a deep learning model to distinguish the cause of optic disc atrophy using retinal fundus photography

The differential diagnosis for optic atrophy can be challenging and requires expensive, time-consuming ancillary testing to determine the cause. While Leber's hereditary optic neuropathy (LHON) and optic neuritis (ON) are both clinically significant causes for optic atrophy, both relatively rare in the general population, contributing to limitations in obtaining large imaging datasets. This study therefore aims to develop a deep learning (DL) model based on small datasets that could distinguish the cause of optic disc atrophy using only fundus photography. We retrospectively reviewed fundus photographs of 120 normal eyes, 30 eyes (15 patients) with genetically-confirmed LHON, and 30 eyes (26 patients) with ON. Images were split into a training dataset and a test dataset and used for model training with ResNet-18. To visualize the critical regions in retinal photographs that are highly associated with disease prediction, Gradient-Weighted Class Activation Map (Grad-CAM) was used to generate image-level attention heat maps and to enhance the interpretability of the DL system. In the 3-class classification of normal, LHON, and ON, the area under the receiver operating characteristic curve (AUROC) was 1.0 for normal, 0.988 for LHON, and 0.990 for ON, clearly differentiating each class from the others with an overall total accuracy of 0.93. Specifically, when distinguishing between normal and disease cases, the precision, recall, and F1 scores were perfect at 1.0. Furthermore, in the differentiation of LHON from other conditions, ON from others, and between LHON and ON, we consistently observed precision, recall, and F1 scores of 0.8. The model performance was maintained until only 10% of the pixel values of the image, identified as important by Grad-CAM, were preserved and the rest were masked, followed by retraining and evaluation.

Clinical Characteristics of m.11778G>A Leber Hereditary Optic Neuropathy with Favorable Outcomes

ABSTRACT The prognosis of 11,778 mitochondrial mutations in Leber hereditary optic neuropathy (LHON) is poor. Patients with favorable outcomes (visual acuity better than 20/100) who could be observed for more than 6 months were analyzed. Among 74 patients (57 male, 17 female), 6 (8.1%) showed improvement in visual acuity of 20/100 or higher. The patients with favorable outcomes have better visual acuity at nadir (logMAR 0.98 ± 0.69 in the favorable patients and logMAR 2.32 ± 0.93 in the unfavorable patients, p = .003). Among the favorable group, four patients (36, 32, 19, and 7 years of age at onset) took idebenone within 6 months of onset. However, fifty-one percent of the patients with unfavorable outcomes took idebenone (p = .008). Although the age at onset in the favorable patients is relatively younger than that of the unfavorable patients (20.3 ± 10.8 versus 28.8 ± 12.8 years), a significant difference was not found (p = .138). In conclusion, better visual acuity in nadir and administration of idebenone may affect vision recovery.

Prophylactic nicotinamide treatment protects from rotenone-induced neurodegeneration by increasing mitochondrial content and volume

Leber’s hereditary optic neuropathy (LHON) is driven by mtDNA mutations affecting Complex I presenting as progressive retinal ganglion cell dysfunction usually in the absence of extra-ophthalmic symptoms. There are no long-term neuroprotective agents for LHON. Oral nicotinamide provides a robust neuroprotective effect against mitochondrial and metabolic dysfunction in other retinal injuries. We explored the potential for nicotinamide to protect mitochondria in LHON by modelling the disease in mice through intravitreal injection of the Complex I inhibitor rotenone. Using MitoV mice expressing a mitochondrial-tagged YFP in retinal ganglion cells we assessed mitochondrial morphology through super-resolution imaging and digital reconstruction. Rotenone induced Complex I inhibition resulted in retinal ganglion cell wide mitochondrial loss and fragmentation. This was prevented by oral nicotinamide treatment. Mitochondrial ultrastructure was quantified by transition electron microscopy, demonstrating a loss of cristae density following rotenone injection, which was also prevented by nicotinamide treatment. These results demonstrate that nicotinamide protects mitochondria during Complex I dysfunction. Nicotinamide has the potential to be a useful treatment strategy for LHON to limit retinal ganglion cell degeneration.

Peripapillary retinal nerve fibre layer thinning, perfusion changes and optic neuropathy in carriers of Leber hereditary optic neuropathy-associated mitochondrial variants

BackgroundWe investigated Leber hereditary optic neuropathy (LHON) families for variation in peripapillary retinal nerve fibre layer thickness and perfusion, and associated optic nerve dysfunction.MethodA group of LHON-affected patients (n=12) and...

Exome Sequencing Reveals a Rare Autosomal Dominant Variant in MSTO1 Gene as a Novel Leber’s Hereditary Optic Neuropathy (LHON) Modifier in a Thai Family with High Penetrance of G11778A Mutation

Exome Sequencing Reveals a Rare Autosomal Dominant Variant in MSTO1 Gene as a Novel Leber’s Hereditary Optic Neuropathy (LHON) Modifier in a Thai Family with High Penetrance of G11778A Mutation

Therapeutic benefit of idebenone in patients with Leber hereditary optic neuropathy: The LEROS nonrandomized controlled trial

Leber hereditary optic neuropathy (LHON) is a mitochondrial disease leading to rapid and severe bilateral vision loss. Idebenone has been shown to be effective in stabilizing and restoring vision in patients treated within 1 year of onset of vision loss. The open-label, international, multicenter, natural history-controlled LEROS study (ClinicalTrials.gov NCT02774005) assesses the efficacy and safety of idebenone treatment (900mg/day) in patients with LHON up to 5 years after symptom onset (N= 199) and over a treatment period of 24months, compared to an external natural history control cohort (N= 372), matched by time since symptom onset. LEROS meets its primary endpoint and confirms the long-term efficacy of idebenone in the subacute/dynamic and chronic phases; the treatment effect varies depending on disease phase and the causative mtDNA mutation. The findings of the LEROS study will help guide the clinical management of patients with LHON.

Variant and clinical landscape of Leber hereditary optic neuropathy based on 1516 families with mtDNA variants in a tertiary centre

AimsTo investigate the clinical characteristics of Leber hereditary optic neuropathy (LHON) with mtDNA primary mutations to better understand features associated with prognosis.MethodsThis study enrolled 1540 LHON patients from 1516 unrelated...