Dataset Information

Leber's Hereditary Optic Neuropathy Arising From the Synergy Between ND1 3635G>A Mutation and Mitochondrial YARS2 Mutations.

ABSTRACT:

Purpose

To investigate the mechanism underlying the synergic interaction between Leber's hereditary optic neuropathy (LHON)-associated ND1 and mitochondrial tyrosyl-tRNA synthetase (YARS2) mutations.

Methods

Molecular dynamics simulation and differential scanning fluorimetry were used to evaluate the structure and stability of proteins. The impact of ND1 3635G>A and YARS2 p.G191V mutations on the oxidative phosphorylation machinery was evaluated using blue native gel electrophoresis and enzymatic activities assays. Assessment of reactive oxygen species (ROS) production in cell lines was performed by flow cytometry with MitoSOX Red reagent. Analysis of effect of mutations on autophagy was undertaken via flow cytometry for autophagic flux.

Results

Members of one Chinese family bearing both the YARS2 p.191Gly>Val and m.3635G>A mutations exhibited much higher penetrance of optic neuropathy than those pedigrees carrying only the m.3635G>A mutation. The m.3635G>A (p.Ser110Asn) mutation altered the ND1 structure and function, whereas the p.191Gly>Val mutation affected the stability of YARS2. Lymphoblastoid cell lines harboring both m.3635G>A and p.191Gly>Val mutations revealed more reductions in the levels of mitochondrion-encoding ND1 and CO2 than cells bearing only the m.3635G>A mutation. Strikingly, both m.3635G>A and p.191Gly>Val mutations exhibited decreases in the nucleus-encoding subunits of complex I and IV. These deficiencies manifested greater defects in the stability and activities of complex I and complex IV and overproduction of ROS and promoted greater autophagy in cell lines harboring both m.3635G>A and p.191Gly>Val mutations compared with cells bearing only the m.3635G>A mutation.

Conclusions

Our findings provide new insights into the pathophysiology of LHON arising from the synergy between ND1 3635G>A mutation and mitochondrial YARS2 mutations.

SUBMITTER: Jin X

PROVIDER: S-EPMC8237128 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

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.