Leber's hereditary optic neuropathy (LHON)-associated ND5 12338T > C mutation altered the assembly and function of complex I, apoptosis and mitophagy.

Mutations in mitochondrial DNA (mtDNA) have been associated with Leber's hereditary optic neuropathy (LHON) and their pathophysiology remains poorly understood. In this study, we demonstrated that a missense mutation (m.12338T>C, p.1M>T) in the ND5 gene contributed to the pathogenesis of LHON. The m.12338T>C mutation affected the first methionine (Met1) with a threonine and shortened two amino acids of ND5. We therefore hypothesized that the mutated ND5 perturbed the structure and function of complex I. Using the cybrid cell models, generated by fusing mtDNA-less (ρ°) cells with enucleated cells from LHON patients carrying the m.12338T>C mutation and a control subject belonging to the same mtDNA haplogroup, we demonstrated that the m.12338T>C mutation caused the reduction of ND5 polypeptide, perturbed assemble and activity of complex I. Furthermore, the m.12338T>C mutation caused respiratory deficiency, diminished mitochondrial adenosine triphosphate levels and membrane potential and increased the production of reactive oxygen species. The m.12338T>C mutation promoted apoptosis, evidenced by elevated release of cytochrome c into cytosol and increased levels of apoptosis-activated proteins: caspases 9, 3, 7 and Poly ADP ribose polymerase in the cybrids carrying the m.12338T>C mutation, as compared with control cybrids. Moreover, we also document the involvement of m.12338T>C mutation in decreased mitophagy, as showed by reduced levels of autophagy protein light chain 3 and accumulation of autophagic substrate p62 in the in mutant cybrids as compared with control cybrids. These data demonstrated the direct link between mitochondrial dysfunction caused by complex I mutation and apoptosis or mitophagy. Our findings may provide new insights into the pathophysiology of LHON.

[The role of MT-ND1 m.3635G>A mutation in Leber's hereditary optic neuropathy].

OBJECTIVE: To investigate the role of MT-ND1 m.3635G>A mutation in the pathogenesis of Leber's hereditary optic neuropathy (LHON). METHODS: Biochemical characteristics including the activity of complex Ⅰ, ATP production and oxygen consumption rate among lymphoblastoid cell lines derived from 3 carriers, 3 affected matrilineal relatives of the families and 3 controls were compared. RESULTS: Comparison of mitochondrial functions in lymphoblastoid cell lines of the carriers, patients and controls showed a 51.0% decrease in the activity of complex Ⅰ in patients compared with controls (P<0.05). The m.3635G>A mutation has resulted in decreased efficiency of ATP synthesis (P<0.05). Comparison of oxygen consumption rate showed that the basal OCR (P<0.05), ATP-linked OCR (P<0.05) and the maximum OCR (P<0.05) have all reduced to some extent compared with the controls. CONCLUSION: These results showed that m.3635G>A, as a LHON-associated mutation, can lead to mitochondrial dysfunction.

Development and Validation of a Nomogram Based on Inflammatory Markers for Risk Prediction in Meige Syndrome Patients.

Purpose: Inflammatory markers are known to be associated with many diseases, but their role in Meige syndrome (MS) remains unclear. This study aimed to develop and validate a nomogram for the risk prediction of MS based on inflammatory markers. Patient Data and Methods: Data from 448 consecutive patients with MS at the Third People's Hospital of Henan Province between January 2022 and December 2023 were retrospectively reviewed. The MS cohort was randomly divided into separate training and validation sets. A nomogram was constructed using a multivariate logistic regression model based on data from the training set. The model's performance was validated through cross-validation, receiver operating characteristic (ROC) curve analysis, calibration curve analysis and decision curve analysis (DCA). Results: A total of five predictors, including red blood cell distribution width (RDW), hemoglobin (HGB), high-density lipoprotein cholesterol (HDL-C), the lymphocyte-to-monocyte ratio (LMR), and the systemic immune-inflammation index (SII), were identified using multivariate logistic regression from a total of 11 variables. The cross-validation results indicated the stability of the model constructed with the above five predictors. The model showed moderate predictive ability, with an area under the ROC curve of 0.767 in the training set and 0.735 in the validation set. The calibration curve and DCA results indicate that the model has strong consistency and significant potential for clinical application. Conclusion: We constructed a nomogram based on five risk predictors, RDW, HGB, HDL-C, the LMR and the SII, to predict MS and enhance the predictive accuracy for identifying MS risk.

A novel ADOA-associated OPA1 mutation alters the mitochondrial function, membrane potential, ROS production and apoptosis.

Autosomal dominant optic atrophy (ADOA) is a dominantly inherited optic neuropathy, affecting the specific loss of retinal ganglion cells (RGCs). The majority of affected cases of ADOA are associated with mutations in OPA1 gene. Our previous investigation identified the c.1198C > G (p.P400A) mutation in the OPA1 in a large Han Chinese family with ADOA. In this report, we performed a functional characterization using lymphoblostoid cell lines derived from affected members of this family and control subjects. Mutant cell lines exhibited the aberrant mitochondrial morphology. A ~24.6% decrease in the mitochondrial DNA (mtDNA) copy number was observed in mutant cell lines, as compared with controls. Western blotting analysis revealed the variable reductions (~45.7%) in four mtDNA-encoded polypeptides in mutant cell lines. The impaired mitochondrial translation caused defects in respiratory capacity. Furthermore, defects in mitochondrial ATP synthesis and mitochondrial membrane potential (ΔΨm) were observed in mutant cell lines. These abnormalities resulted in the accumulation of oxidative damage and increasing of apoptosis in the mutant cell lines, as compared with controls. All those alterations may cause the primary degeneration of RGCs and subsequent visual loss. These data provided the direct evidence for c.1198C > G mutation leading to ADOA. Our findings may provide new insights into the understanding of pathophysiology of ADOA.

Mitochondrial ND1 Variants in 1281 Chinese Subjects With Leber's Hereditary Optic Neuropathy.

PURPOSE: The purpose of this study was to investigate the mutational incidence and spectrum of mitochondrial ND1 gene in subjects with Leber's hereditary optic neuropathy (LHON). METHODS: A cohort of 1281 Han Chinese probands and 478 control subjects underwent sequence analysis of mitochondrial (mt)DNA. Resultant variants were evaluated for evolutionary conservation, allelic frequencies, and structural and functional consequences. Respiratory complex activities were measured using lymphoblastoid cell lines derived from 25 probands carrying the mtDNA mutation and 3 controls. RESULTS: Mutational analysis identified 178 (70 missense and 108 silent) variants in the MT-ND1 gene. The incidences of known m.3460G>A, m.3635G>A, m.3733G>A, m.3866T>C, and m.3394T>C mutations were 1.33%, 0.86%, 0.08%, 0.55%, and 2.97%, respectively. Fifteen novel putative mutations were identified in 27 probands, translated into 2.1% cases of this cohort. The activity of complex I in mutant cell lines carrying one of putative mutations ranged from 66% to 76% of the average values in control cell lines, whereas activities of complexes II, III, and IV in mutant cells were comparable with those in controls. The low penetrances of optic neuropathy were observed in pedigrees carrying novel putative mutation(s). Moreover, mtDNAs in 101 probands carrying the MT-ND1 mutation(s) were widely dispersed among 15 Eastern Asian haplogroups. In particular, the occurrences of haplogroups M, M9, and M10 in patients carrying the ND1 mutations were higher than those in controls. CONCLUSIONS: These data demonstrated that the MT-ND1 gene is a hot spot for mutations associated with LHON. Our findings may provide valuable information for pathophysiology, management, and genetic counseling of LHON.