Leber Hereditary Optic Neuropathy: A Mitochondrial Disease Unique in Many Ways

The discovery of a ten-generation m.C1494T pedigree in the east of England with probable links to King Richard III

This paper reports the discovery of a m.C1494T pedigree in the east of England made during a search for matrilineal relations of King Richard III. The mitochondrial DNA variant m.C1494T has been associated with aminoglycoside-induced deafness. This variant is very uncommon. although pedigrees with this variant have previously been found in China and Spain. The members of the newly identified pedigree all belong to the mitochondrial haplogroup J1c2c3, which is also the haplogroup of King Richard III. The presence of a few people in the USA from the same haplogroup has previously been noted, and it is now known that one of the people can show his descent from a couple who lived in Nottinghamshire, England, in the late 1700's. The mitochondrial DNA sequence of this man, at present living in the USA, and of his 4th cousin, twice removed, living in Lincoln, England, has shown they belong to haplogroup J1c2c3 and both have the variant m.C1494T; thereby, allowing the production of a multi-generational pedigree originating in the east of England. Fortunately, deafness has not been found in any living member of this large pedigree. It was also noted that the link to the family of King Richard III has not been firmly defined; however the circumstantial evidence is strong as many of his family members lived in this part of England.

Dysregulation of the circRNA_0087207/miR-548c-3p/PLSR1-TGFB2 axis in Leber hereditary optic neuropathy in vitro

BACKGROUND

Leber hereditary optic neuropathy (LHON) is mainly the degeneration of retinal ganglion cells (RGCs) associated with high apoptosis and reactive oxygen species (ROS) levels, which is accepted to be caused by the mutations in the subunits of complex I of the mitochondrial electron transport chain. The treatment is still infant while efforts of correcting genes or using antioxidants do not bring good and consistent results. Unaffected carrier carries LHON mutation but shows normal phenotype, suggesting that the disease's pathogenesis is complex, in which secondary factors exist and cooperate with the primary complex I dysfunction.

METHODS

Using LHON patient-specific induced pluripotent stem cells (iPSCs) as the in vitro disease model, we previously demonstrated that circRNA_0087207 had the most significantly higher expression level in the LHON patient-iPSC-derived RGCs compared with the unaffected carrier-iPSC-derived RGCs. To elaborate the underlying pathologies regulated by circRNA_008720 mechanistically, bioinformatics analysis was conducted and elucidated that circRNA_0087207 could act as a sponge of miR-548c-3p and modulate PLSCR1/TGFB2 levels in ND4 mutation-carrying LHON patient-iPSC-derived RGCs.

RESULTS

Using LHON iPSC-derived RGCs as the disease-based platform, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis on targeted mRNA of miR-548c-3p showed the connection with apoptosis, suggesting downregulation of miR548c-3p contributes to the apoptosis of LHON patient RGCs.

CONCLUSION

We showed that the downregulation of miR548c-3p plays a critical role in modulating cellular dysfunction and the apoptotic program of RGCs in LHON.

GenEye24: Novel rapid screening test for the top-3 Leber's Hereditary Optic Neuropathy pathogenic sequence variants

Leber's Hereditary Optic Neuropathy (LHON) has been mainly (90-95 %) associated to one of three variants: m.3460G>A, m.11778G>A, m.14484T>C. Herein, a screening method was developed for its detection, supporting clinical/therapeutics decision. It relies on real-time PCR with High-Resolution Melting (HRM) analysis. Variant classification is made using HRM Software and quality controls. A total of 101 samples were analyzed. All samples were correctly assigned: 58 wild-type, 35 positive for m.11778G>A, 6 positive for m.14484T>C, 2 positive for m.3460G>A. Results presented sensitivity = 1, specificity = 1, Positive Predictive Value = 1 and Negative Predictive Value = 1. A new Real-Time PCR/HRM screening method cost-efficient, simple, robust and quick, detecting LHON's top-3 is described.

Relative Leukocyte Telomere Length and Telomerase Complex Regulatory Markers Association with Leber's Hereditary Optic Neuropathy

Background and Objectives: To evaluate the association of relative leukocyte telomere length (RLTL) and telomerase complex regulatory markers with Leber’s hereditary optic neuropathy (LHON). Material and Methods: A case-control study was performed in patients with LHON (≥18 years) and healthy subjects. The diagnosis of LHON was based on a genetic blood test (next-generation sequencing with Illumina MiSeq, computer analysis: BWA2.1 Illumina BaseSpace, Alamut, and mtDNA Variant analyzer 1000 were performed) and diagnostic criteria approved by the LHON disease protocol. Statistical analysis was performed using the standard statistical software package, IBM SPSS Statistics 27. Statistically significant results were considered when p < 0.05. Results: Significantly longer RLTL was observed in LHON patients than in healthy controls (p < 0.001). RLTL was significantly longer in women and men with LOHN than in healthy women and men in the control group (p < 0.001 and p = 0.003, respectively). In the elderly group (>32 years), RLTL was statistically significantly longer in LHON patients compared with healthy subjects (p < 0.001). The GG genotype of the TERC rs12696304 polymorphism was found to be statistically significantly higher in the LHON group (p = 0.041), and the C allele in the TERC rs12696304 polymorphism was found to be statistically significantly less common in the LHON group (p < 0.001). The RLTL of LHON patients was found to be statistically significantly longer in the TERC rs12696304 polymorphism in all tested genotypes (CC, p = 0.005; CG, p = 0.008; GG, p = 0.025), TEP1 rs1760904 polymorphism in the GA genotype (p < 0.001), and TEP1 gene rs1713418 in the AA and AG genotypes (p = 0.011 and p < 0.001, respectively). Conclusions: The RLTL in LHON patients was found to be longer than in healthy subjects regardless of treatment with idebenone. The TERC rs12696304 polymorphism, of all studied polymorphisms, was the most significantly associated with changes in LHON and telomere length.

Clinical Overview of Leber Hereditary Optic Neuropathy

Leber hereditary ptic neuropathy (LHON) is a disease of young adults with bilateral, painless, subacute visual loss. The peak age of onset of LHON is in the second and third decades of life. Men are 4 times more likely to be affected than women. In about 25-50% of cases, both eyes are affected simultaneously. In unilateral cases, the other eye is usually affected 2 to 3 months later. Visual acuity deteriorates to counting fingers or worse with a dense central or centrocecal scotoma. In the subacute phase, the optic disc may appear hyperemic with swelling of the peripapillary retinal nerve fibre layer, peripapillary telangiectasias, and increased vascular tortuosity. Ocular coherence tomography of the macula shows marked thinning of the ganglion cell complex even at this stage. The diagnosis of LHON is made in a subject with a consistent clinical history and/or one of three common pathogenic mitochondrial DNA (mtDNA) variants identified by molecular genetic testing. Idebenone was approved by the European Medicines Agency under exceptional circumstances for the treatment of LHON. Current evidence suggests some benefit to vision in a subset of affected individuals treated with idebenone, particularly when treated within the first year of onset of vision loss. In this article, we discuss aetiology, clinical features, diagnosis, differential dignosis, prognosis and treatment.

Role of Oxidative Stress in Ocular Diseases Associated with Retinal Ganglion Cells Degeneration

Ocular diseases associated with retinal ganglion cell (RGC) degeneration is the most common neurodegenerative disorder that causes irreversible blindness worldwide. It is characterized by visual field defects and progressive optic nerve atrophy. The underlying pathophysiology and mechanisms of RGC degeneration in several ocular diseases remain largely unknown. RGCs are a population of central nervous system neurons, with their soma located in the retina and long axons that extend through the optic nerve to form distal terminals and connections in the brain. Because of this unique cytoarchitecture and highly compartmentalized energy demand, RGCs are highly mitochondrial-dependent for adenosine triphosphate (ATP) production. Recently, oxidative stress and mitochondrial dysfunction have been found to be the principal mechanisms in RGC degeneration as well as in other neurodegenerative disorders. Here, we review the role of oxidative stress in several ocular diseases associated with RGC degenerations, including glaucoma, hereditary optic atrophy, inflammatory optic neuritis, ischemic optic neuropathy, traumatic optic neuropathy, and drug toxicity. We also review experimental approaches using cell and animal models for research on the underlying mechanisms of RGC degeneration. Lastly, we discuss the application of antioxidants as a potential future therapy for the ocular diseases associated with RGC degenerations.

Leber hereditary optic neuropathy and dystonia overlapping mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes due to m.14459G>A mutation

OBJECTIVE

To report a Chinese family with combined m.14459G>A mutation and m.6064A>T mutation of which the female proband presenting unique Leber hereditary optic neuropathy and dystonia (LDYT) overlapping mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) phenotype.

METHODS

Clinical information of the pedigree was collected. We performed muscle biopsy and whole-length mitochondrial DNA (mtDNA) sequencing on the proband. The activity of respiratory chain complexes in immortalized lymphoblasts was determined.

RESULTS

The current 23-year-old proband suffered from vision decline at age 15 and developed seizures and dystonia with bilateral lesions in precentral gyri at age 18. When she was 21, the lesions in bilateral putamen were found with elevated cerebrospinal fluid lactate. Her mother had optic atrophy; one of her brother died at age 4 with respiratory distress; and the other 8-year-old brother was asymptomatic. Muscle biopsy of the proband was unremarkable. The mtDNA sequencing revealed a heteroplasmic m.14459G>A mutation and a previously unreported m.6064A>T mutation. The respiratory chain complex I activity in the proband's immortalized lymphoblasts was 50% less than the normal control; while there was no statistical difference between the proband and the normal control in the activity of complex IV.

CONCLUSIONS

We presented the first case exhibiting LDYT and MELAS phenotype with m.14459G>A mutation, and the decreased complex I activity contributed to the pathogenicity. Our study expanded the clinical spectrum of m.14459G>A mutation.

Current and Emerging Treatment Modalities for Leber's Hereditary Optic Neuropathy: A Review of the Literature

Introduction

The purpose of this review is to present the current and emerging treatment alternatives for Leber’s hereditary optic neuropathy (LHON), emphasizing the most recent use of idebenone and stem cells or gene therapy.

Methods

A comprehensive literature review was performed at the PubMed database regarding the various treatment modalities for LHON.

Results

Treatment modalities for LHON include nutritional supplements, activators of mitochondrial biogenesis, brimonidine, and symptomatic and supportive treatment, but nowadays attention is being paid to idebenone and gene therapy or stem cells.

Conclusion

The treatment of LHON remains challenging, given the nature of the disease and its prognosis.