Emerging model systems and treatment approaches for Leber's hereditary optic neuropathy: Challenges and opportunities.
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ABSTRACT:
SUBMITTER: Bahr T
PROVIDER: S-EPMC9252426 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Many human childhood mitochondrial disorders result from abnormal mitochondrial DNA (mtDNA) and altered bioenergetics. These abnormalities span most of the mtDNA, demonstrating that there are no "unique" positions on the mitochondrial genome that when deleted or mutated produce a disease phenotype. This diversity implies that the relationship between mitochondrial genotype and clinical phenotype is very complex. The origins of clinical phenotypes are thus unclear, fundamentally difficult-to-treat, and are usually clinically devastating. Current treatment is largely supportive and the disorders progress relentlessly causing significant morbidity and mortality. Vitamin supplements and pharmacological agents have been used in isolated cases and clinical trials, but the efficacy of these interventions is unclear. In spite of recent advances in the understanding of the pathogenesis of mitochondrial diseases, a cure remains elusive. An optimal cure would be gene therapy, which involves introducing the missing gene(s) into the mitochondria to complement the defect. Our recent research results indicate the feasibility of an innovative protein-transduction ("protofection") technology, consisting of a recombinant mitochondrial transcription factor A (TFAM) that avidly binds mtDNA and permits efficient targeting into mitochondria in situ and in vivo. Thus, the development of gene therapy for treating mitochondrial disease offers promise, because it may circumvent the clinical abnormalities and the current inability to treat individual disorders in affected individuals. This review aims to focus on current treatment options and future therapeutics in mitochondrial disease treatment with a special emphasis on Leber's hereditary optic neuropathy.
| S-EPMC5652312 | biostudies-literature
Project description:Cybrid technology was used to replace Leber hereditary optic neuropathy (LHON) causing mitochondrial DNA (mtDNA) mutations from patient-specific fibroblasts with wildtype mtDNA, and mutation-free induced pluripotent stem cells (iPSCs) were generated subsequently. Retinal ganglion cell (RGC) differentiation demonstrates increased cell death in LHON-RGCs and can be rescued in cybrid corrected RGCs.
| S-EPMC5425131 | biostudies-literature
Project description:Leber's hereditary optic neuropathy, the most frequent mitochondrial disease due to mitochondrial DNA point mutations in complex I, is characterized by the selective degeneration of retinal ganglion cells, leading to optic atrophy and loss of central vision prevalently in young males. The current study investigated the reasons for the higher prevalence of Leber's hereditary optic neuropathy in males, exploring the potential compensatory effects of oestrogens on mutant cell metabolism. Control and Leber's hereditary optic neuropathy osteosarcoma-derived cybrids (11778/ND4, 3460/ND1 and 14484/ND6) were grown in glucose or glucose-free, galactose-supplemented medium. After having shown the nuclear and mitochondrial localization of oestrogen receptors in cybrids, experiments were carried out by adding 100 nM of 17?-oestradiol. In a set of experiments, cells were pre-incubated with the oestrogen receptor antagonist ICI 182780. Leber's hereditary optic neuropathy cybrids in galactose medium presented overproduction of reactive oxygen species, which led to decrease in mitochondrial membrane potential, increased apoptotic rate, loss of cell viability and hyper-fragmented mitochondrial morphology compared with control cybrids. Treatment with 17?-oestradiol significantly rescued these pathological features and led to the activation of the antioxidant enzyme superoxide dismutase 2. In addition, 17?-oestradiol induced a general activation of mitochondrial biogenesis and a small although significant improvement in energetic competence. All these effects were oestrogen receptor mediated. Finally, we showed that the oestrogen receptor ? localizes to the mitochondrial network of human retinal ganglion cells. Our results strongly support a metabolic basis for the unexplained male prevalence in Leber's hereditary optic neuropathy and hold promises for a therapeutic use for oestrogen-like molecules.
| S-EPMC3025718 | biostudies-literature
Project description: Not available
| S-EPMC7141913 | biostudies-literature
Project description:Mutations to the ND5 gene are uncommonly associated with Leber's hereditary optic neuropathy (LHON). Herein, we describe a 57-year-old man with the m. 13528A>G, p. (Thr398Ala) mutation at the ND5 gene who presented with progressive bilateral vision loss over the course of 3 months. He had a significant history of smoking and alcohol consumption. Visual field testing demonstrated bilateral central scotomas. At 2-year follow-up, his visual acuity improved relative to baseline and temporal optic disc pallor was observed in both eyes. There are scarce reports of this mutation in the literature, and this case report further expands the clinical presentation of the m. 13528A>G mutation at the ND5 gene in patients with LHON phenotype.
| S-EPMC10020936 | biostudies-literature
Project description:Leber's hereditary optic neuropathy (LHON) is a maternally transmitted disorder caused by point mutations in mitochondrial DNA (mtDNA). Most cases are due to mutations in genes encoding subunits of the NADH-ubiquinone oxidoreductase that is Complex I of the electron transport chain (ETC). These mutations are located at nucleotide positions 3460, 11778, or 14484 in the mitochondrial genome. The disease is characterized by apoplectic, bilateral, and severe visual loss. While the mutated mtDNA impairs generation of ATP by all mitochondria, there is only a selective loss of retinal ganglion cells and degeneration of optic nerve axons. Thus, blindness is typically permanent. Half of the men and 10% of females who harbor the pathogenic mtDNA mutation actually develop the phenotype. This incomplete penetrance and gender bias is not fully understood. Additional mitochondrial and/or nuclear genetic factors may modulate the phenotypic expression of LHON. In a population-based study, the mtDNA background of haplogroup J was associated with an inverse relationship of low-ATP generation and increased production of reactive oxygen species (ROS). Effective therapy for LHON has been elusive. In this paper, we describe the findings of pertinent published studies and discuss the controversies of potential strategies to ameliorate the disease.
| S-EPMC3021870 | biostudies-literature
Project description:Leber's hereditary optic neuropathy (LHON) is a maternally inherited eye disease. X-linked nuclear modifiers were proposed to modify the phenotypic manifestation of LHON-associated mitochondrial DNA (mtDNA) mutations. By whole-exome sequencing, we identified the X-linked LHON modifier (c.157C>T, p.Arg53Trp) in PRICKLE3 encoding a mitochondrial protein linked to biogenesis of ATPase in 3 Chinese families. All affected individuals carried both ND4 11778G>A and p.Arg53Trp mutations, while subjects bearing only a single mutation exhibited normal vision. The cells carrying the p.Arg53Trp mutation exhibited defective assembly, stability, and function of ATP synthase, verified by PRICKLE3-knockdown cells. Coimmunoprecipitation indicated the direct interaction of PRICKLE3 with ATP synthase via ATP8. Strikingly, cells bearing both p.Arg53Trp and m.11778G>A mutations displayed greater mitochondrial dysfunction than those carrying only a single mutation. This finding indicated that the p.Arg53Trp mutation acted in synergy with the m.11778G>A mutation and deteriorated mitochondrial dysfunctions necessary for the expression of LHON. Furthermore, we demonstrated that Prickle3-deficient mice exhibited pronounced ATPase deficiencies. Prickle3-knockout mice recapitulated LHON phenotypes with retinal deficiencies, including degeneration of retinal ganglion cells and abnormal vasculature. Our findings provided new insights into the pathophysiology of LHON that were manifested by interaction between mtDNA mutations and X-linked nuclear modifiers.
| S-EPMC7456240 | biostudies-literature
Project description:PurposePeripapillary vascular alterations have been classically described as hallmarks of Leber's Hereditary Optic Neuropathy (LHON). We recently demonstrated microvascular pathology involving the macula in patients affected with chronic LHON using optical coherence tomography angiography (OCTA). Macular vascular pathology in acute LHON has not previously been reported.MethodsThe macular superficial vasculature of an asymptomatic carrier and an affected patient with acute LHON, mitochondrial DNA mutation 3460, was assessed by OCTA.ResultsSimilar findings of peripapillary microangiopathy and vascular telangiectasias were seen the affected patient, but in the parafoveal macula. These changes were most prominent nasally and inferiorly, corresponding to the proximal portions of the papillomacular bundle. The foveal avascular zone was markedly enlarged in the affected patient relative to the asymptomatic mother.ConclusionsThese findings in acute LHON further supports the clinical utility of vascular parameters and suggest that further studies focused on macular pathology may be warranted to assess the natural history of LHON.
| S-EPMC6247405 | biostudies-literature
Project description:Leber's hereditary optic neuropathy (LHON) is the most frequent mitochondrial disease and was the first to be genetically defined by a point mutation in mitochondrial DNA (mtDNA). A molecular diagnosis is achieved in up to 95% of cases, the vast majority of which are accounted for by 3 mutations within mitochondrial complex I subunit-encoding genes in the mtDNA (mtLHON). Here, we resolve the enigma of LHON in the absence of pathogenic mtDNA mutations. We describe biallelic mutations in a nuclear encoded gene, DNAJC30, in 33 unsolved patients from 29 families and establish an autosomal recessive mode of inheritance for LHON (arLHON), which to date has been a prime example of a maternally inherited disorder. Remarkably, all hallmarks of mtLHON were recapitulated, including incomplete penetrance, male predominance, and significant idebenone responsivity. Moreover, by tracking protein turnover in patient-derived cell lines and a DNAJC30-knockout cellular model, we measured reduced turnover of specific complex I N-module subunits and a resultant impairment of complex I function. These results demonstrate that DNAJC30 is a chaperone protein needed for the efficient exchange of complex I subunits exposed to reactive oxygen species and integral to a mitochondrial complex I repair mechanism, thereby providing the first example to our knowledge of a disease resulting from impaired exchange of assembled respiratory chain subunits.
| S-EPMC7954600 | biostudies-literature
Project description:PurposeTo screen mitochondrial DNA (mtDNA) variations in Leber hereditary optic neuropathy (LHON).MethodsTen LHON patients were selected from neuro-ophthalmology clinics of All India Institute of Medical Sciences (AIIMS), New Delhi, India. Clinical evaluation included slit-lamp biomicroscopy, fundus examination, and neuroimaging. DNA was isolated from whole blood samples. The entire coding region of the mitochondrial genome was amplified by PCR in ten patients and 20 controls. The full mtDNA genome except D-loop was sequenced. All sequences were analyzed against mitochondrial reference sequence NC_012920.ResultsMtDNA sequencing revealed a total of 30 nucleotide variations in the ten LHON patients and 29 in the 20 controls. Of 30 changes, 30.00% (9/30) were nonsynonymous, and the remaining 70.00% (21/30) were synonymous. In controls, a total of five changes were nonsynonymous. Out of the total 14 nonsynonymous changes observed in cases and controls, four (p.A52T in nicotinamide adenine dinucleotide [NADH] dehydrogenase [ND1] protein; p.L128Q in ND2; p.W48R in ATPase6; p.R340H in ND4 protein) were pathogenic. Four patients were positive for either of pathogenic changes. In total, 16.66% (5/30) variations were novel out of which 40.00% (2/5) were nonsynonymous. All novel variations were submitted to the GenBank database, and accession numbers were obtained. Primary LHON mutations in complex I genes have been considered a hallmark feature of LHON patients, and primary LHON mutations were present in two cases in this study. Mutations in complex I genes (ND genes) account for 50%-90% of LHON pedigrees in different ethnic pedigrees. In this study the highest numbers of changes were also present in complex I genes (46.66%; 14/30) followed by complex IV (30.00%; 9/30), complex III (16.66%; 5/30), and then complex V (6.66%; 2/30). Complex I had 5/30 (16.66%) nonsynonymous changes, complex III had 1/30 (3.33%), complex IV had 1/30 (3.33%), and complex V had 2/30 (6.66%) nonsynonymous changes. Nonsynonymous mutations in cytochrome c oxidase (COX) genes have been reported previously in LHON patients. Nonsynonymous mtDNA variations may adversely affect the respiratory chain and impair the oxidative phosphorylation (OXPHOS) pathway, resulting in low ATP production and elevated reactive oxygen species (ROS) levels, which cause oxidative stress. It has previously been reported that oxidative stress (OS) leads to oxidative damage of cellular macromolecules, such as mitochondrial and nuclear DNA, proteins, and lipids along with energy depletion and a local imbalance of calcium homeostasis, resulting in neuronal degeneration. OS is the underlying etiology in several ocular diseases and also plays an essential role in LHON.ConclusionsA total of five novel mtDNA variations were identified in this study. Nonsynonymous mtDNA variations may adversely affect the respiratory chain and impair the OXPHOS pathway, resulting in low ATP production and elevated ROS levels. OS further damages both nuclear and mtDNA. This preliminary study describes mtDNA sequence variations in a relatively small number of LHON patients of north Indian ethnic origin. However, these results should be confirmed in other populations. Early diagnosis of mtDNA variations and prompt anti-oxidant administration in these cases may delay OS-induced injury to retinal ganglion cells (RGCs) and hence improve visual prognosis.
| S-EPMC2862244 | biostudies-literature