Variants found in the respiratory complex I (CI) subunit genes encoded by mitochondrial DNA can cause severe genetic diseases. However, it is difficult to establish a priori whether a single or a combination of CI variants may impact oxidative phosphorylation. Here we propose a computational approach based on coarse-grained molecular dynamics simulations aimed at investigating new CI variants. One of the primary CI variants associated with the Leber hereditary optic neuropathy (m.14484T>C/MT-ND6) was used as a test case and was investigated alone or in combination with two additional rare CI variants whose role remains uncertain. We found that the primary variant positioned in the E-channel region, which is fundamental for CI function, stiffens the enzyme dynamics. Moreover, a new mechanism for the transition between π- and α-conformation in the helix carrying the primary variant is proposed. This may have implications for the E-channel opening/closing mechanism. Finally, our findings show that one of the rare variants, located next to the primary one, further worsens the stiffening, while the other rare variant does not affect CI function. This approach may be extended to other variants candidate to exert a pathogenic impact on CI dynamics, or to investigate the interaction of multiple variants.

Recently, Stenton et al. (2021) described a new, autosomal recessive inheritance pattern of Leber\'s hereditary optic neuropathy (LHON) caused by missense variants in the DNAJC30 gene. The DNAJC30 c.152A > G, p.(Tyr51Cys) variant was by far the most common variant reported in patients originating from Eastern Europe, therefore, it is believed to be a founder variant in these populations. We report the first two cases of DNAJC30-linked autosomal recessive LHON in a young male and a female originating from Estonia. The patients presented severe loss of central vision and clinical features indistinguishable from mitochondrial LHON. The whole exome sequencing carried out in the male patient and the next-generation sequencing panel in the young female patient identified the same homozygous missense variant in the DNAJC30 gene. Our cases further reinforce the pathogenicity of c.152A > G, p.(Tyr51Cys) DNAJC30 variant causing autosomal recessive LHON. According to the gnomAD database, the allele frequency of this variant in the Estonian population is 0.8%, translating into a prevalence of carriers of 1:60. It is the highest among different gnomAD populations. Applying the Hardy-Weinberg equation, an estimated 92 persons in the Estonian population carry the homozygous variant c.152A > G, p.(Tyr51Cys) in DNAJC30. In patients with LHON, we advise sequencing both the DNAJC30 gene and mitochondrial DNA simultaneously.

To analyze the functional and structural changes in retinal ganglion cells (RGCs) and their axons that occur during Leber\'s hereditary optic neuropathy (LHON) using photopic negative response (PhNR) and spectral domain optical coherence tomography (SD-OCT).
Individuals diagnosed with LHON and their family members were invited to participate in this cross-sectional study. PhNR and OCT were used. The PhNR amplitude and peripapillary retinal nerve fiber layer (pRNFL) thicknesses were compared among the three groups. In addition, affected individuals were divided into subacute, dynamic and chronic phases based on disease duration in order to evaluate the decay in RGCs function and structure.
73 affected and 30 carriers with a m.11778G > A mutation were included. PhNR amplitude and the thickness of pRNFL significantly decreased in affected individuals and carriers compared to that of the controls (P＜0.001). However, there was no difference between the carriers and the controls (P＞0.05). There was no difference in the PhNR amplitude of different phases (P = 0.464). In the subacute phase, only temporal pRNFL thickness decreased significantly (P＜0.001). PRNFL thickness decreased significantly in dynamic phase (P＜0.001). Temporal pRNFL thickness continued to decrease in the chronic phase (P = 0.042).
In the subacute phase, the function of RGCs was severely impaired. Thickness of pRNFL decreased significantly in four quadrants during disease progression. In the chronic phase, pRNFL thickness decreased slightly. Carriers have shown RGCs dysfunction before pathological changes occur, suggesting subclinical abnormalities.

Leber\'s hereditary optic neuropathy (LHON) is a maternally inherited disease caused by a mutation of mitochondrial DNA. LHON targets retinal ganglion cells (RGC), whose axons form the optic nerve. The mutation that leads to LHON is silent until an unknown trigger causes dysfunction of complex I in the mitochondria of RGC. This results in discontinuation of RGC energy production and, eventually, RGC apoptosis. Patients experience bilateral sequential central scotoma over the course of a few months, with a minority recovering some vision more than 1 year after the onset of visual loss. No pharmacological treatment is recommended unless patients are symptomatic in at least one eye, as most LHON mutation carriers never experience visual loss. Research has been focused on treatments that are thought to restore the mitochondrial electron transport chain in RGC in patients with recent disease onset (<1 year). Significant advances have been made in evaluating free radical cell scavengers and gene therapy as potential treatments for LHON. Although promising, the results of clinical trials have been mixed. In patients with chronic visual loss for more than 1 year, treatment that restores vision is yet to be discovered. In this review, we summarize management strategies for patients with LHON before, during, and after the loss of vision, explain the rationale and effectiveness of previous and current treatments, and report findings about emerging treatments.

暂无摘要。

Purpose: To compare peripapillary choroidal vascularity among Leber\'s Hereditary Optic Neuropathy (LHON) patients at different stages of natural course and healthy controls using optical coherence tomography (OCT), and to evaluate peripapillary choroidal vascularity changes in LHON patients before and after gene therapy. Methods: 57 LHON patients and 15 healthy controls were enrolled in this prospective clinical study. LHON patients were divided into three duration groups based on stage of disease progression. Both patients and healthy controls underwent OCT scans focused on the optic disc at baseline with Heidelberg Spectralis, and patients underwent OCT at 1, 3, and 6 months after gene therapy. OCT images were converted and binarized using ImageJ software. Choroidal thickness (CT), total choroidal area (TCA), and choroidal vascularity index (CVI) in each quadrant of OCT images were measured to evaluate peripapillary choroidal vascularity. Results: At baseline, the average CT was not significantly different between LHON patients at different stages and between healthy controls (P = 0.468). Although average TCA and average CVI were slightly higher in LHON patients at different stages than in healthy controls, the difference was not statistically significant (P = 0.282 and 0.812, respectively). After gene therapy, The average TCA at 1 month after gene therapy was significantly higher than that before gene therapy (P = 0.003), while no significant differences were found in the average CT or average CVI in LHON patients before and 1,3 and 6 months after gene therapy using pairwise comparisons (all P > 0.05). Conclusions: No significant difference was found in choroidal vascularity of LHON patients at different stages and healthy controls. Choroidal vascularity seems to stay stable after gene therapy.

Leber\'s hereditary optic neuropathy (LHON) is a rare inherited blindness caused by mutations in the mitochondrial DNA (mtDNA). The disorder is untreatable and tricky, as the existing chemotherapeutic agent Idebenone alleviates symptoms rather than overcoming the underlying cause. Although some studies have made progress on allotopic expression for LHON, in situ mitochondrial gene therapy remains challenging, which may simplify delivery procedures to be a promising therapeutic for LHON. LHON becomes more difficult to manage in the changed mitochondrial microenvironment, including increasing reactive oxygen species (ROS) and decreasing mitochondrial membrane potential (MMP). Herein, a pathologically responsive mitochondrial gene delivery vector named [triphenylphosphine-terminated poly(sulfur-containing thioketal undecafluorohexylamine histamine) and Ide-terminated poly(sulfur-containing thioketal undecafluorohexylamine histamine)] (TISUH) is reported to facilitate commendable in situ mitochondrial gene therapy for LHON. TISUH directly targets diseased mitochondria via triphenylphosphine and fluorination addressing the decreasing MMP. In addition, TISUH can be disassembled by high mitochondrial ROS levels to release functional genes for enhancing gene transfection efficiency and fundamentally correcting genetic abnormalities. In both traditional and gene-mutation-induced LHON mouse models, TISUH-mediated gene therapy shows satisfactory curative effect through the sustained therapeutic protein expression in vivo. This work proposes a novel pathologically responsive in situ mitochondrial delivery platform and provides a promising approach for refractory LHON as well as other mtDNA mutated diseases treatments.

BACKGROUND: Multiple sclerosis-related optic neuritis is mostly associated with good recovery. The aim of this study was to investigate the causes of progressive visual worsening in multiple sclerosis patients despite treatment.
METHODS: We retrospectively reviewed the medical records of multiple sclerosis patients with optic neuritis admitted to the ward of our Neurology Department between 2001 and 2020. The patients with unilateral/bilateral progressive visual loss or non-substantial recovery of visual acuity were screened for genetic testing for Leber\'s hereditary optic neuropathy.
RESULTS: Of 1014 multiple sclerosis patients, 411 (39%) reported having optic neuritis. During follow-up, 11 patients manifested atypical characteristics of multiple sclerosis-related optic neuritis (presence of one of the following clinical findings: bilateral simultaneous or sequential eye involvement, progressive visual loss, or no response to corticosteroids during hospitalization), while others presented with typical multiple sclerosis-related optic neuritis. Those multiple sclerosis patients with atypical characteristics of optic neuritis were screened for other possible etiologies of optic neuropathy. We found pathogenic mitochondrial mutations in 5 patients with multiple sclerosis in our study group.
CONCLUSIONS: In our study group, the prevalence of mitochondrial mutations among all multiple sclerosis patients with optic neuritis was 0.12%. We strongly recommend investigating Leber\'s hereditary optic neuropathy mutations in MS patients if they suffer from severe or bilateral visual loss without recovery during follow-up. Because Leber\'s hereditary optic neuropathy mitochondrial mutations indicate relatively poor visual prognosis and have important implications for genetic counseling.

More than 30 years after discovering Leber\'s hereditary optic neuropathy (LHON) as the first maternally inherited disease associated with homoplasmic mtDNA mutations, we still struggle to achieve effective therapies. LHON is characterized by selective degeneration of retinal ganglion cells (RGCs) and is the most frequent mitochondrial disease, which leads young people to blindness, in particular males. Despite that causative mutations are present in all tissues, only a specific cell type is affected. Our deep understanding of the pathogenic mechanisms in LHON is hampered by the lack of appropriate models since investigations have been traditionally performed in non-neuronal cells. Effective in-vitro models of LHON are now emerging, casting promise to speed our understanding of pathophysiology and test therapeutic strategies to accelerate translation into clinic. We here review the potentials of these new models and their impact on the future of LHON patients.

Objective: Mitochondrial 13513G>A mutation presenting as isolated Leber\'s hereditary optic neuropathy (LHON) without any extraocular pathology has not been reported in literature. We herein evaluate the clinical characteristics and heteroplasmy of m.13513G>A mutation manifesting as isolated LHON. Methods: Seven members of a Chinese family were enrolled in this study. All subjects underwent detailed systemic and ophthalmic examinations. Mitochondrial DNA in their blood was assessed by targeted PCR amplifications, next generation sequencing (NGS), and pyrosequencing. One hundred of blood samples from ethnic-matched healthy volunteers were tested by NGS and pyrosequencing as normal controls. Results: Isolated LHON without any other ocular or extraocular pathology was identified in a 16 year old patient in this family. Heteroplasmic m.13513G>A mutation was detected by NGS of the full mtDNA genome in the patient with mutant load of 33.56%, and of 26% 3 months and 3 years after the onset of LHON, respectively. No m.13513G>A mutation was detected in all his relatives by NGS. Pyrosequencing revealed the mutant load of m.13513G>A mutation of the LHON patient, his mother, father and sister were 22.4, 1.9, 0, and 0%, respectively. None of 100 healthy control subjects was detected to harbor m.13513G>A mutation either by NGS or by pyrosequencing of the full mt DNA genome. Conclusions: We first report m.13513G>A mutation with low mutant load presenting as isolated LHON. NGS of the full mitochondrial DNA genome is highly recommended for LHON suspects when targeted PCR amplification for main primary point mutations of LHON was negative.