mtDNA Mutations Research Articles

The clinical and genetic spectrum of mitochondrial diseases in China: A multicenter retrospective cross-sectional study.

Mitochondrial diseases (MtDs) present diverse clinical phenotypes, yet large-scale studies are hindered by their rarity. This retrospective, multicenter study, conducted across five Chinese hospitals' neurology departments from 2009 to 2019, aimed to address this gap. Nationwide, 1351 patients were enrolled, with a median onset age of 14.0 (18.5) years. The predominant phenotype was mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) (45.0%). Mitochondrial DNA (mtDNA) mutations were prevalent (87.4%), with m.3243A>G being the most common locus (48.7%). Meanwhile, POLG mutations in nuclear DNA (nDNA) accounted for 16.5%. Comparative analysis based on age groups (with a cut-off at 14 years) revealed the highest prevalence of MELAS, with Leigh syndrome (LS) and chronic progressive external ophthalmoplegia (CPEO) being the second most common phenotypes in junior and senior groups, respectively. Notably, the most commonly mutated nuclear genes varied across age groups. In conclusion, MELAS predominated in this Chinese MtD cohort, underscored by m.3243A>G and POLG as principal mtDNA mutations and pathogenic nuclear genes. The phenotypic and genotypic disparities observed among different age cohorts highlight the complex nature of MtDs.

MSC-mediated mitochondrial transfer restores mitochondrial DNA and function in neural progenitor cells of Leber's hereditary optic neuropathy.

Leber's hereditary optic neuropathy (LHON) is a debilitating mitochondrial disease associated with mutations in mitochondrial DNA (mtDNA). Unfortunately, the available treatment options for LHON patients are limited due to challenges in mitochondrial replacement. In our study, we reprogramming LHON urine cells into induced pluripotent stem cells (iPSCs) and differentiating them into neural progenitor cells (NPCs) and neurons for disease modeling. Our research revealed that LHON neurons exhibited significantly higher levels of mtDNA mutations and reduced mitochondrial function, confirming the disease phenotype. However, through co-culturing LHON iPSC-derived NPCs with mesenchymal stem cells (MSCs), we observed a remarkable rescue of mutant mtDNA and a significant improvement in mitochondrial metabolic function in LHON neurons. These findings suggest that co-culturing with MSCs can enhance mitochondrial function in LHON NPCs, even after their differentiation into neurons. This discovery holds promise as a potential therapeutic strategy for LHON patients.

Real-time assessment of mitochondrial DNA heteroplasmy dynamics at the single-cell level.

Mitochondrial DNA (mtDNA) is present in multiple copies within cells and is required for mitochondrial ATP generation. Even within individual cells, mtDNA copies can differ in their sequence, a state known as heteroplasmy. The principles underlying dynamic changes in the degree of heteroplasmy remain incompletely understood, due to the inability to monitor this phenomenon in real time. Here, we employ mtDNA-based fluorescent markers, microfluidics, and automated cell tracking, to follow mtDNA variants in live heteroplasmic yeast populations at the single-cell level. This approach, in combination with direct mtDNA tracking and data-driven mathematical modeling reveals asymmetric partitioning of mtDNA copies during cell division, as well as limited mitochondrial fusion and fission frequencies, as critical driving forces for mtDNA variant segregation. Given that our approach also facilitates assessment of segregation between intact and mutant mtDNA, we anticipate that it will be instrumental in elucidating the mechanisms underlying the purifying selection of mtDNA.

Pediatric Chordoma: A Tale of Two Genomes.

Little is known about the genomic alterations in chordoma, with the exception of loss of SMARCB1, a core member of the SWI/SNF complex, in poorly differentiated chordomas. A TBXT duplication and rs2305089 polymorphism, located at 6q27, are known genetic susceptibility loci. A comprehensive genomic analysis of the nuclear and mitochondrial genomes in pediatric chordoma has not yet been reported. In this study, we performed WES and mtDNA genome sequencing on 29 chordomas from 23 pediatric patients. Findings were compared with that from whole-genome sequencing datasets of 80 adult patients with skull base chordoma. In the pediatric chordoma cohort, 81% of the somatic mtDNA mutations were observed in NADH complex genes, which is significantly enriched compared with the rest of the mtDNA genes (P = 0.001). In adult chordomas, mtDNA mutations were also enriched in the NADH complex genes (P < 0.0001). Furthermore, a progressive increase in heteroplasmy of nonsynonymous mtDNA mutations was noted in patients with multiple tumors (P = 0.0007). In the nuclear genome, rare likely germline in-frame indels in ARID1B, a member of the SWI/SNF complex located at 6q25.3, were observed in five pediatric patients (22%) and four patients in the adult cohort (5%). The frequency of rare ARID1B indels in the pediatric cohort is significantly higher than that in the adult cohort (P = 0.0236, Fisher's exact test), but they were both significantly higher than that in the ethnicity-matched populations (P < 5.9e-07 and P < 0.0001174, respectively). Implications: germline ARID1B indels and mtDNA aberrations seem important for chordoma genesis, especially in pediatric chordoma.

LRPPRC and SLIRP synergize to maintain sufficient and orderly mammalian mitochondrial translation.

In mammals, the leucine-rich pentatricopeptide repeat protein (LRPPRC) and the stem-loop interacting RNA-binding protein (SLIRP) form a complex in the mitochondrial matrix that is required throughout the life cycle of most mitochondrial mRNAs. Although pathogenic mutations in the LRPPRC and SLIRP genes cause devastating human mitochondrial diseases, the in vivo function of the corresponding proteins is incompletely understood. We show here that loss of SLIRP in mice causes a decrease of complex I levels whereas other OXPHOS complexes are unaffected. We generated knock-in mice to study the in vivo interdependency of SLIRP and LRPPRC by mutating specific amino acids necessary for protein complex formation. When protein complex formation is disrupted, LRPPRC is partially degraded and SLIRP disappears. Livers from Lrpprc knock-in mice had impaired mitochondrial translation except for a marked increase in the synthesis of ATP8. Furthermore, the introduction of a heteroplasmic pathogenic mtDNA mutation (m.C5024T of the tRNAAla gene) into Slirp knockout mice causes an additive effect on mitochondrial translation leading to embryonic lethality and reduced growth of mouse embryonic fibroblasts. To summarize, we report that the LRPPRC/SLIRP protein complex is critical for maintaining normal complex I levels and that it also coordinates mitochondrial translation in a tissue-specific manner.

Misregulation of mitochondrial 6mA promotes the propagation of mutant mtDNA and causes aging in C.elegans.

In virtually all eukaryotes, the mitochondrial DNA (mtDNA) encodes proteins necessary for oxidative phosphorylation (OXPHOS) and RNAs required for their synthesis. The mechanisms of regulation of mtDNA copy number and expression are not completely understood but crucially ensure the correct stoichiometric assembly of OXPHOS complexes from nuclear- and mtDNA-encoded subunits. Here, we detect adenosine N6-methylation (6mA) on the mtDNA of diverse animal and plant species. This modification is regulated in C.elegans by the DNA methyltransferase DAMT-1 and demethylase ALKB-1. Misregulation of mtDNA 6mA through targeted modulation of these activities inappropriately alters mtDNA copy number and transcript levels, impairing OXPHOS function, elevating oxidative stress, and shortening lifespan. Compounding these defects, mtDNA 6mA hypomethylation promotes the cross-generational propagation of a deleterious mtDNA. Together, these results reveal that mtDNA 6mA is highly conserved among eukaryotes and regulates lifespan by influencing mtDNA copy number, expression, and heritable mutation levels invivo.

Maternal age enhances purifying selection on pathogenic mutations in complex I genes of mammalian mtDNA.

Mitochondrial diseases, caused mainly by pathogenic mitochondrial DNA (mtDNA) mutations, pose major challenges due to the lack of effective treatments. Investigating the patterns of maternal transmission of mitochondrial diseases could pave the way for preventive approaches. In this study, we used DddA-derived cytosine base editors (DdCBEs) to generate two mouse models, each haboring a single pathogenic mutation in complex I genes (ND1 and ND5), replicating those found in human patients. Our findings revealed that both mutations are under strong purifying selection during maternal transmission and occur predominantly during postnatal oocyte maturation, with increased protein synthesis playing a vital role. Interestingly, we discovered that maternal age intensifies the purifying selection, suggesting that older maternal age may offer a protective effect against the transmission of deleterious mtDNA mutations, contradicting the conventional notion that maternal age correlates with increased transmitted mtDNA mutations. As collecting comprehensive clinical data is needed to understand the relationship between maternal age and transmission patterns in humans, our findings may have profound implications for reproductive counseling of mitochondrial diseases, especially those involving complex I gene mutations.

Single-mitochondrion sequencing uncovers distinct mutational patterns and heteroplasmy landscape in mouse astrocytes and neurons

BackgroundMitochondrial (mt) heteroplasmy can cause adverse biological consequences when deleterious mtDNA mutations accumulate disrupting “normal” mt-driven processes and cellular functions. To investigate the heteroplasmy of such mtDNA changes, we developed a moderate throughput mt isolation procedure to quantify the mt single-nucleotide variant (SNV) landscape in individual mouse neurons and astrocytes. In this study, we amplified mt-genomes from 1645 single mitochondria isolated from mouse single astrocytes and neurons to (1) determine the distribution and proportion of mt-SNVs as well as mutation pattern in specific target regions across the mt-genome, (2) assess differences in mtDNA SNVs between neurons and astrocytes, and (3) study co-segregation of variants in the mouse mtDNA.Results(1) The data show that specific sites of the mt-genome are permissive to SNV presentation while others appear to be under stringent purifying selection. Nested hierarchical analysis at the levels of mitochondrion, cell, and mouse reveals distinct patterns of inter- and intra-cellular variation for mt-SNVs at different sites. (2) Further, differences in the SNV incidence were observed between mouse neurons and astrocytes for two mt-SNV 9027:G > A and 9419:C > T showing variation in the mutational propensity between these cell types. Purifying selection was observed in neurons as shown by the Ka/Ks statistic, suggesting that neurons are under stronger evolutionary constraint as compared to astrocytes. (3) Intriguingly, these data show strong linkage between the SNV sites at nucleotide positions 9027 and 9461.ConclusionsThis study suggests that segregation as well as clonal expansion of mt-SNVs is specific to individual genomic loci, which is important foundational data in understanding of heteroplasmy and disease thresholds for mutation of pathogenic variants.

The three-parent baby: Medicolegal, forensic and ethical concerns.

In the recent past, human genetics and in vitro fertilization (IVF) have undergone various advances to combat with several congenital and developmental disorders. These advances are a boon for the families and patients who were restricted from having a child due to one or the other reasons. One such reason is the mitochondrial DNA (mtDNA) mutations, which are definitely transmitted from the mother to the child due to uniparental/maternal inheritance of mitochondria. Depending upon the range of the mutation (mutation loads) present, the mtDNA mutation leads to various devitalizing to fatal disorders, all of which are incurable. Scientists and researchers developed a technique known as mitochondrial donation technique or mitochondrial replacement therapy (MRT) to combat with the mtDNA mutations. The technique relies on the replacement of faulty mitochondria in the mother's egg with the normal wild-type from a donor female resulting in a "three-parent baby." On the other side, forensic scientists and anthropologists continuously explore the mtDNA in various medicolegal cases and in uncoupling the mystery of human origin and migration respectively. In this regard, we explored the genetic, forensic and ethical aspects of a "three-parent baby." The present communication also attempts to highlight the importance and limitations of the MRT technique/three-parent baby in a medicolegal context.

Unravelling the origins and forces that shape mtDNA mutations in human cells.

Unravelling the origins and forces that shape mtDNA mutations in human cells.

Necrosis drives susceptibility to Mycobacterium tuberculosis in POLG mtDNA mutator mice.

The genetic and molecular determinants that underlie the heterogeneity of Mycobacterium tuberculosis (Mtb) infection outcomes in humans are poorly understood. Multiple lines of evidence demonstrate that mitochondrial dysfunction can exacerbate mycobacterial disease severity and mutations in some mitochondrial genes confer susceptibility to mycobacterial infection in humans. Here, we report that mutations in mitochondria DNA (mtDNA) polymerase gamma (POLG) potentiate susceptibility to Mtb infection in mice. POLG mutator mtDNA mice fail to mount a protective innate immune response at an early infection timepoint, evidenced by high bacterial burdens, reduced M1 macrophages, and excessive neutrophil infiltration in the lungs. Immunohistochemistry reveals signs of enhanced necrosis in the lungs of Mtb-infected POLG mice and POLG mutator macrophages are hyper-susceptible to extrinsic triggers of necroptosis ex vivo. By assigning a role for mtDNA mutations in driving necrosis during Mtb infection, this work further highlights the requirement for mitochondrial homeostasis in mounting balanced immune responses to Mtb.

Mitochondrial DNA mosaicism in normal human somatic cells

Somatic cells accumulate genomic alterations with age; however, our understanding of mitochondrial DNA (mtDNA) mosaicism remains limited. Here we investigated the genomes of 2,096 clones derived from three cell types across 31 donors, identifying 6,451 mtDNA variants with heteroplasmy levels of ≳0.3%. While the majority of these variants were unique to individual clones, suggesting stochastic acquisition with age, 409 variants (6%) were shared across multiple embryonic lineages, indicating their origin from heteroplasmy in fertilized eggs. The mutational spectrum exhibited replication-strand bias, implicating mtDNA replication as a major mutational process. We evaluated the mtDNA mutation rate (5.0 × 10−8 per base pair) and a turnover frequency of 10–20 per year, which are fundamental components shaping the landscape of mtDNA mosaicism over a lifetime. The expansion of mtDNA-truncating mutations toward homoplasmy was substantially suppressed. Our findings provide comprehensive insights into the origins, dynamics and functional consequences of mtDNA mosaicism in human somatic cells.

Significantly reduced, but balanced, rates of mitochondrial fission and fusion are sufficient to maintain the integrity of yeast mitochondrial DNA.

Mitochondria exist as dynamic tubular networks and the morphology of these networks impacts organelle function and cell health. Mitochondrial morphology is maintained in part by the opposing activities of mitochondrial fission and fusion. Mitochondrial fission and fusion are also required to maintain mitochondrial DNA (mtDNA) integrity. In Saccharomyces cerevisiae , the simultaneous inhibition of mitochondrial fission and fusion results in increased mtDNA mutation and the consequent loss of respiratory competence. The mechanism by which fission and fusion maintain mtDNA integrity is not fully understood. Previous work demonstrates that mtDNA is spatially linked to mitochondrial fission sites. Here, we extend this finding using live-cell imaging to localize mtDNA to mitochondrial fusion sites. While mtDNA is present at sites of mitochondrial fission and fusion, mitochondrial fission and fusion rates are not altered in cells lacking mtDNA. Using alleles that alter mitochondrial fission and fusion rates, we find that mtDNA integrity can be maintained in cells with significantly reduced, but balanced, rates of fission and fusion. In addition, we find that increasing mtDNA copy number reduces the loss of respiratory competence in double mitochondrial fission-fusion mutants. Our findings add novel insights into the relationship between mitochondrial dynamics and mtDNA integrity.

Mitochondrial DNA mutations attenuate Bleomycin-induced dermal fibrosis by inhibiting differentiation into myofibroblasts

Post-mitotic, non-proliferative dermal fibroblasts have crucial functions in maintenance and restoration of tissue homeostasis. They are involved in essential processes such as wound healing, pigmentation and hair growth, but also tumor development and aging-associated diseases. These processes are energetically highly demanding and error prone when mitochondrial damage occurs. However, mitochondrial function in fibroblasts and the influence of mitochondrial dysfunction on fibroblast-specific demands are still unclear. To address these questions, we created a mouse model in which accelerated cell-specific mitochondrial DNA (mtDNA) damage accumulates. We crossed mice carrying a dominant-negative mutant of the mitochondrial replicative helicase Twinkle (RosaSTOP system) with mice that express fibroblast-specific Cre Recombinase (Collagen1A2 CreERT) which can be activated by Tamoxifen (TwinkleFIBRO). Thus, we are able to induce mtDNA deletions and duplications in specific cells, a process which resembles the physiological aging process in humans, where this damage accumulates in all tissues. Upon proliferation in vitro, Tamoxifen induced Twinkle fibroblasts deplete most of their mitochondrial DNA which, although not disturbing the stoichiometry of the respiratory chain complexes, leads to reduced ROS production and mitochondrial membrane potential as well as an anti-inflammatory and anti-fibrotic profile of the cells. In Sodium Azide treated wildtype fibroblasts, without a functioning respiratory chain, we observe the opposite, a rather pro-inflammatory and pro-fibrotic signature. Upon accumulation of mitochondrial DNA mutations in vivo the TwinkleFIBRO mice are protected from fibrosis development induced by intradermal Bleomycin injections. This is due to dampened differentiation of the dermal fibroblasts into α−smooth-muscle-actin positive myofibroblasts in TwinkleFIBRO mice. We thus provide evidence for striking differences of the impact that mtDNA mutations have in contrast to blunted mitochondrial function in dermal fibroblasts and skin homeostasis. These data contribute to improved understanding of mitochondrial function and dysfunction in skin and provide mechanistic insight into potential targets to treat skin fibrosis in the future.

A Preliminary Study of the Occurrence of Genetic Changes in mtDNA in the Muscles in Children Treated for Strabismus.

Background: The dysregulation of extraocular muscles (EOMs) in the strabismus may be partly due to modification in the mitochondrial DNA (mtDNA). Currently, little is known about changes occurring in mtDNA of EOMs in patients with strabismus, therefore the aim of our study was to analyze if there are any changes occurring in the mitochondrial DNA of extraocular muscles in children that underwent strabismus surgery in our clinic. Methods: MtDNA was isolated from the tissue material using the Qiagen kit. Assessment of mtDNA mutations was performed by next-generation sequencing (NGS) using the Illumina MiSeq protocol. Results: The examination revealed the presence of atrophic changes in muscle fibers. NGS evaluation revealed a dominant genetic mutation in the ANT1 gene in 12 of the 15 patients examined. Conclusions: The presented results constitute the beginning of research on changes in mtDNA occurring in the muscles of children with strabismus surgery. Further studies are necessary in the context of resolving the transcriptomic differences between strabismic and non-strabismic EOMs. Better understanding of the molecular genetics of strabismus will lead to improved knowledge of the disease mechanisms and ultimately to a more effective treatment.

Dissecting the sequential evolution of a selfish mitochondrial genome in Caenorhabditis elegans

Mitochondrial genomes exist in a nested hierarchy of populations where mitochondrial variants are subject to genetic drift and selection at each level of organization, sometimes engendering conflict between different levels of selection, and between the nuclear and mitochondrial genomes. Deletion mutants in the Caenorhabditis elegans mitochondrial genome can reach high intracellular frequencies despite strongly detrimental effects on fitness. During a mutation accumulation (MA) experiment in C. elegans, a 499 bp deletion in ctb-1 rose to 90% frequency within cells while significantly reducing fitness. During the experiment, the deletion-bearing mtDNA acquired three additional mutations in nd5, namely two single insertion frameshift mutations in a homopolymeric run, and a base substitution. Despite an additional fitness cost of these secondary mutations, all deletion-bearing molecules contained the nd5 mutations at the termination of the MA experiment. The presence of mutant mtDNA was associated with increased mtDNA copy-number. Variation in mtDNA copy-number was greater in the MA lines than in a wildtype nuclear background, including a severe reduction in copy-number at one generational timepoint. Evolutionary replay experiments using different generations of the MA experiment as starting points suggests that two of the secondary mutations contribute to the proliferation of the original ctb-1 deletion by unknown mechanisms.

O-275 Prenatal genetic screening to assess mtDNA disease occurrence in children

Abstract Study question Can prenatal genetic testing accurately predict mtDNA mutation load anddisease transmission to children for families affected by Leigh Syndrome? Summary answer Whole genome mtDNA sequencing for 13513G&amp;gt;A mutation in chorionic villi and amniotic fluid was similar to those measured in babies suggesting accuracy of disease prediction. What is known already Severity of mtDNA disease in children depends on heteroplasmy levels(proportion of mutant to wild-type mtDNA). There is a minimum threshold for the mutant mtDNA heteroplasmy (typically 60%) above which oxidative metabolism is impaired to cause disease. Predicting the disease based on the mutation load measured during embryonic or fetal development is critically needed. However, preimplantation genetics screening for many mtDNA mutations has limitations due to the potential increase in heteroplasmy levels after implantation. We hypothesized that prenatal screening of chorionic villi and/or amniotic fluid during the first trimester of pregnancy could provide more reliable diagnosis of disease occurrence in children. Study design, size, duration We evaluated mtDNA heteroplasmy in biopsies collected from chorionic villi and amniotic fluid at 10- and 16-weeks of gestation, respectively, for two consecutive, naturally conceived pregnancies for a carrier of 13513G&amp;gt;A mutation. Sequencing results were compared to mutations in the blood, skin, and urine of children after birth. Both children were also extensively monitored for a few years for disease occurrence. Participants/materials, setting, methods A family with maternally transmitted Leigh Syndrome including both parents and two existing children were enrolled during the initial phase. Whole mtDNA sequencing was used to confirm the maternal transmission of the mutation by analysis of blood, skin, and urine from asymptomatic parents and the older son and the severely affected younger son. Furthermore, prenatal diagnostics were performed for two consecutive pregnancies and children after birth. Main results and the role of chance The mother carried 13513G&amp;gt;A mutation in the skin (91% heteroplasmy), urine(39%), and blood (6.8%), while no mutation was detected in the father’s samples. The asymptomatic eldest child revealed a low mutation in the skin (14%), urine(23%), and blood (10%). While the younger son diagnosed with Leigh syndrome carried 56% mutation in blood, 86% in skin, and 97% in urine. Heteroplasmy ranging from 0.6% to 40% was also measured in 4 individual immature oocytes retrieved upon hormonal stimulation of the carrier. The family later naturally conceived 2 consecutive pregnancies and requested help with prenatal diagnostics. In the first pregnancy, mutation loads were 27.5% in chorionic villi and 29.5% in amniotic fluid. The family decided to keep the pregnancy which resulted in the birth of a healthy child with low mutations in blood (0.07%) and skin (14.5%). In the second pregnancy, prenatal diagnostics in CVS showed low mutation at 0.11%, resulting in the birth of an unaffected child with mutation loads of 1.4% in blood and 0% in skin. Limitations, reasons for caution Genetic counseling for mtDNA disease transmission is difficult due tocomplex inheritance of heteroplasmic variants for various pathogenicmutations. Inheritance and distribution of mtDNA mutations also influencedby individual family genetics. Therefore, prenatal diagnostic screeningshould be cautiously considered based on the specific circumstances for eachfamily. Wider implications of the findings Prenatal genetic diagnostics for families with mtDNA disease based on whole mtDNA sequencing by the qualified laboratory may accurately predict heteroplasmy levels and disease occurrence in children. However, careful analysis of family history and the likelihood of having low mutation load oocytes was critical for the success of our case. Trial registration number N/A

A Comprehensive Review of Leber Hereditary Optic Neuropathy and Its Association with Multiple Sclerosis-Like Phenotypes Known as Harding's Disease.

Leber Hereditary Optic Neuropathy (LHON) stands as a distinctive maternally inherited mitochondrial disorder marked by painless, subacute central vision loss, primarily affecting young males. This review covers the possible relationship between LHON and multiple sclerosis (MS), covering genetic mutations, clinical presentations, imaging findings, and treatment options. LHON is associated with mutations in mitochondrial DNA (mtDNA), notably m.11778G>A, m.3460G>A, and m.14484T>C, affecting complex I subunits. Beyond ocular manifestations, LHON can go beyond the eye into a multi-systemic disorder, showcasing extraocular abnormalities. Clinical presentations, varying in gender prevalence and outcomes, underscore the nature of mitochondrial optic neuropathies. Hypotheses exploring the connection between LHON and MS encompass mitochondrial DNA mutations triggering neurological diseases, immunologically mediated responses inducing demyelination, and the possibility of coincidental diseases. The research on mtDNA mutations among MS patients sheds light on potential associations with specific clinical subgroups, offering a unique perspective into the broader landscape of MS. Imaging findings, ranging from white matter alterations to cerebrospinal fluid biomarkers, further emphasize shared pathological processes between LHON-MS and classical MS. This comprehensive review contributes to the understanding of the complex relationship between LHON and MS.

Alterations in coenzyme Q10 status in a cybrid line harboring the 3243A>G mutation of mitochondrial DNA is associated with abnormal mitochondrial bioenergetics and dysregulated mitochondrial biogenesis

Mitochondrial DNA (mtDNA) mutations, including the m.3243A>G mutation that causes mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), are associated with secondary coenzyme Q10 (CoQ10) deficiency. We previously demonstrated that PPARGC1A knockdown repressed the expression of PDSS2 and several COQ genes. In the present study, we compared the mitochondrial function, CoQ10 status, and levels of PDSS and COQ proteins and genes between mutant cybrids harboring the m.3243A>G mutation and wild-type cybrids. Decreased mitochondrial energy production, defective respiratory function, and reduced CoQ10 levels were observed in the mutant cybrids. The ubiquinol-10:ubiquinone-10 ratio was lower in the mutant cybrids, indicating blockage of the electron transfer upstream of CoQ, as evident from the reduced ratio upon rotenone treatment and increased ratio upon antimycin A treatment in 143B cells. The mutant cybrids exhibited downregulation of PDSS2 and several COQ genes and upregulation of COQ8A. In these cybrids, the levels of PDSS2, COQ3-a isoform, COQ4, and COQ9 were reduced, whereas those of COQ3-b and COQ8A were elevated. The mutant cybrids had repressed PPARGC1A expression, elevated ATP5A levels, and reduced levels of mtDNA-encoded proteins, nuclear DNA-encoded subunits of respiratory enzyme complexes, MNRR1, cytochrome c, and DHODH, but no change in TFAM, TOM20, and VDAC1 levels. Alterations in the CoQ10 level in MELAS may be associated with mitochondrial energy deficiency and abnormal gene regulation. The finding of a reduction in the ubiquinol-10:ubiquinone-10 ratio in the MELAS mutant cybrids differs from our previous discovery that cybrids harboring the m.8344A>G mutation exhibit a high ubiquinol-10:ubiquinone-10 ratio.

Topical nanoencapsulated cannabidiol cream as an innovative strategy combating UV-A–induced nuclear and mitochondrial DNA injury: A pilot randomized clinical study

BackgroundUltraviolet-A radiation (UVA) contributes to photoaging/photocarcinogenesis by generating inflammation and oxidative damage. Current photoprotective strategies are limited by availability/utilization of UVA filters, highlighting an unmet need. Cannabidiol (CBD), having anti-inflammatory/antioxidant properties via regulation of NFR-2, HMOX1, and PPAR-y, could potentially mitigate damage from UVA exposure. Objective/MethodsProspective, single-center, pilot clinical trial (NCT05279495). Nineteen participants applied nano-CBD (nCBD) or vehicle (VC) cream to randomized, blinded buttock sites twice-daily for 14-days, then treated sites were irradiated with ≤3x UVA minimal erythema dose. After 24-hours, punch biopsies were obtained for histology, immunohistochemistry, real-time PCR. ResultsAt 24-hours, 21% of participants had less observed erythema on CBD-treated skin than VC skin. Histologically, nCBD-treated skin had reduced UVA-induced epidermal hyperplasia than VC (p=0.01). Immunohistochemistry detected reduced cytoplasmic/nuclear 8-oxo-guanine glycosylase 1 staining in nCBD-treated skin compared to VC (p<0.01). Quantitative mtDNA PCR demonstrated UVA-induced deletion of ND4 (proxy:4977bp deletion; p=0.003) and ND1 (proxy:3895bp deletion; p=0.002) were significantly reduced by in vivo nCBD treatment compared to VC. LimitationsSample size. ConclusionTopically applied nCBD cream reduced UVA-induced formation of a frequent mutagenic nuclear DNA base lesion and protected against mtDNA mutations associated with UVA-induced skin aging. This trial is the first to identify UV-protective capacity of CBD-containing topicals in humans.