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We report the case of a 24-year-old previously healthy man who presented with an unusual combination of myelin oligodendrocyte glycoprotein antibody-associated optic neuritis (MOG-ON) and Leber’s hereditary optic neuropathy (LHON). Initially experiencing two episodes of painless visual acuity reduction, the patient responded well to glucocorticoid therapy, coinciding with an MOG antibody titre of 1:32. However, a subsequent third episode of painless vision loss did not improve with continued glucocorticoid treatment. Further diagnostic workup revealed a mitochondrial DNA mutation (11778 G>A), confirming the diagnosis of LHON. This unique presentation highlights the necessity of considering multiple aetiologies in cases of optic neuropathy where the cause is not immediately apparent, especially when the response to standard treatments is inconsistent. Our findings suggest that dual pathologies may coexist and should be considered in unexplained cases of optic neuropathy to facilitate appropriate clinical management. [ABSTRACT FROM AUTHOR]

Leber’s hereditary optic neuropathy (LHON) causes subacute visual loss, and, in the acute phase, the optic disc shows hyperemia, peripapillary telangiectasia, and swelling of the retinal nerve fiber layer (RNFL). Rarely, retinal hemorrhage may be present. In this study, we investigated LHON cases with retinal hemorrhage in the acute phase. Among 82 cases (164 eyes) of LHON who visited the Inoue Eye Hospital, retinal hemorrhage was observed in 5 cases (5 eyes). The age at onset was 36 (27–46) years, with 4 male cases. Mitochondrial DNA analysis revealed the presence of the m.11778G > A variant in four patients and the m.14484T > C variant in one patient. There was no medical history and no excessive smoking or alcohol consumption in any of the cases. In all cases, retinal hemorrhages were observed in the RNFL, accompanying the characteristic optic disc findings of LHON. Fluorescein angiography performed in three cases showed no leakage from the optic disc or blood vessels. While rare, the presence of retinal hemorrhage along the RNFL during the acute phase of LHON should be recognized, as it may warrant consideration of alternative diagnoses. [ABSTRACT FROM AUTHOR]

Background: To investigate the peripapillary retinal nerve fibre layer (RNFL) thickness changes and analyse factors associated with visual recovery of G11778A Leber hereditary optic neuropathy (LHON) patients. Methods: Patients diagnosed with G11778A LHON between July 2017 and December 2020 in Tongji hospital were included in this follow-up study. Patients were grouped according to disease duration. Variations in the RNFL thickness in each quadrant at different disease stages were characterised using optical coherence tomography. According to the absence or presence of significant visual acuity improvements, LHON patients of disease duration ≥ 6 months were divided into two groups. A bivariate logistic regression model was constructed to analyse the potential factors associated with spontaneous visual recovery. Results: This study included 56 G11778A LHON patients (112 eyes) and 25 healthy controls (50 eyes), with a mean follow-up of 5.25 ± 1.42 months. All quadrants and mean RNFL thicknesses of LHON patients first increased and then decreased, except for the temporal RNFL. As the disease progressed, RNFL thinning slowed; however, gradual RNFL thinning occurred. Logistic regression revealed that baseline best corrected visual acuity was related to spontaneous visual recovery of LHON patients with disease duration ≥ 6 months. Conclusion: The pattern of RNFL involvement could be helpful in the differential diagnosis of LHON and other optic neuropathies. LHON patients with better vision are more likely to experience some degree of spontaneous visual acuity recovery after the subacute phase. [ABSTRACT FROM AUTHOR]

Accumulative evidence indicates a critical role of mitochondrial function in autism spectrum disorders (ASD), implying that ASD risk may be linked to mitochondrial dysfunction due to DNA (mtDNA) variations. Although a few studies have explored the association between mtDNA variations and ASD, the role of mtDNA in ASD is still unclear. Here, we aimed to investigate whether mitochondrial DNA haplogroups are associated with the risk of ASD. Two European cohorts and an Ashkenazi Jewish (AJ) cohort were analyzed, including 2,062 ASD patients in comparison with 4,632 healthy controls. DNA samples were genotyped using Illumina HumanHap550/610 and Illumina 1M arrays, inclusive of mitochondrial markers. Mitochondrial DNA (mtDNA) haplogroups were identified from genotyping data using HaploGrep2. A mitochondrial genome imputation pipeline was established to detect mtDNA variants. We conducted a case-control study to investigate potential associations of mtDNA haplogroups and variants with the susceptibility to ASD. We observed that the ancient adaptive mtDNA haplogroup K was significantly associated with decreased risk of ASD by the investigation of 2 European cohorts including a total of 2,006 cases and 4,435 controls (odds ratio = 0.64, P= 1.79 × 10–5), and we replicated this association in an Ashkenazi Jewish (AJ) cohort including 56 cases and 197 controls (odds ratio = 0.35, P = 9.46 × 10–3). Moreover, we demonstrate that the mtDNA variants rs28358571, rs28358584, and rs28358280 are significantly associated with ASD risk. Further expression quantitative trait loci (eQTLs) analysis indicated that the rs28358584 and rs28358280 genotypes are associated with expression levels of nearby genes in brain tissues, suggesting those mtDNA variants may confer risk for ASD via regulation of expression levels of genes encoded by the mitochondrial genome. This study helps to shed light on the contribution of mitochondria in ASD and provides new insights into the genetic mechanism underlying ASD, suggesting the potential involvement of mtDNA-encoded proteins in the development of ASD. Increasing evidence indicates that mitochondrial dysfunction may be linked to autism spectrum disorder (ASD). This study investigated potential associations of mitochondrial DNA (mtDNA) variants in 2 European and Ashkenazi Jewish cohorts including 2,062 individuals with ASD and 4,632 healthy controls. Researchers found that the ancient mtDNA haplogroup K was linked to a reduced risk of ASD in both European and Ashkenazi Jewish populations. Additionally, specific mtDNA variants were associated with ASD risk and were shown to influence the expression of nearby genes in the brain. These findings highlight the potential involvement of mtDNA in ASD development, offering new insights into the genetic mechanisms underlying the disorder. [ABSTRACT FROM AUTHOR]

CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss) syndrome is a rare genetic disorder caused by the heterozygous mutation, c.2452G > A, in the ATP1A3 gene. CAPOS syndrome involves a characteristic episode in which neuropathy develops after a fever in childhood, and here, we describe the case of a patient with CAPOS syndrome. The patient had repeated episodes of a fever around 74 months of age. Although he could speak at 23 months of age, he presented with hearing difficulty after the fever. Pure-tone audiometry revealed moderate-to-severe bilateral sensorineural hearing loss, and auditory brainstem response (ABR) showed poor response in the both ears. Auditory stead-state response (ASSR) produced relatively consistent results compared to pure-tone audiometry. A mutation in the ATP1A3 gene was detected through genetic testing. In CAPOS syndrome, a genetic mutation leads to desynchronization during neural firing. We believe that this desynchronization in neural firing is responsible for the lack of response in the ABR and the presence of a response in the ASSR. In this patient, we attribute the response detection in ASSR to its greater tolerance for errors in the timing of neural firing compared to ABR. [ABSTRACT FROM AUTHOR]

Endometrial cancer (EC) is a devastating and common disease affecting women’s health. The NCI Surveillance, Epidemiology, and End Results Program predicted that there would be >66,000 new cases in the United States and >13,000 deaths from EC in 2023, and EC is the sixth most common cancer among women worldwide. Regulation of mitochondrial metabolism plays a role in tumorigenesis. In proliferating cancer cells, mitochondria provide the necessary building blocks for biosynthesis of amino acids, lipids, nucleotides, and glucose. One mechanism causing altered mitochondrial activity is mitochondrial DNA (mtDNA) mutation. The polyploid human mtDNA genome is a circular double-stranded molecule essential to vertebrate life that harbors genes critical for oxidative phosphorylation plus mitochondrial-derived peptide genes. Cancer cells display aerobic glycolysis, known as the Warburg effect, which arises from the needs of fast-dividing cells and is characterized by increased glucose uptake and conversion of glucose to lactate. Solid tumors often contain at least one mtDNA substitution. Furthermore, it is common for cancer cells to harbor mixtures of wild-type and mutant mtDNA genotypes, known as heteroplasmy. Considering the increase in cancer cell energy demand, the presence of functionally relevant carcinogenesis-inducing or environment-adapting mtDNA mutations in cancer seems plausible. We review 279 EC tumor-specific mtDNA single nucleotide variants from 111 individuals from different studies. Many transition mutations indicative of error-prone DNA polymerase γ replication and C to U deamination events were present. We examine the spectrum of mutations and their heteroplasmy and discuss the potential biological impact of recurrent, non-synonymous, insertion, and deletion mutations. Lastly, we explore current EC treatments, exploiting cancer cell mitochondria for therapy and the prospect of using mtDNA variants as an EC biomarker. [ABSTRACT FROM AUTHOR]

A recent study published in the journal Molecular Biomedicine explores the dynamics of hematopoietic stem cells (HSCs) through mitochondrial mutation profiling. The study introduces a new technology called ReDeeM, which combines single-cell transcriptomics and chromatin accessibility analysis to accurately capture the natural barcodes of single cells. By using this technology, researchers were able to generate clone-resolved single-cell transcriptome and chromatin maps of human hematopoietic cells, providing new insights into the clonal behavior of HSCs in maintaining blood system function and in aging and disease. The study also identified major hematopoietic cell types and revealed stable molecular and behavioral heterogeneity among HSCs. However, further validation and exploration are needed to address limitations and improve the understanding of cell subpopulations. [Extracted from the article]

Key Clinical Message: We report on the successful use of chemotherapy for treatment of stage 2B testicular seminoma in a carrier of the Leber's hereditary optic neuropathy 11778 mitochondrial mutation. Neurotoxic chemotherapy may not prompt disease conversion. [ABSTRACT FROM AUTHOR]

Background: Previous studies have implicated inherited mutations in mitochondrial DNA (mtDNA) in sensorineural hearing loss (SNHL). However, the definitive association between mitochondrial 12S rRNA (MT-RNR1) variants and hearing loss in the population has not been well established, particularly in Asia. The objective of this retrospective cohort study was to assess the association between MT-RNR1 variants and the risk of SNHL in patients in Taiwan. Methods: The cohort included 306,068 participants from Taiwan between January 2003 and December 2020. Participants were classified based on genetic variants, particularly mitochondrial mutations (rs267606618, rs267606619, rs267606617). MT-RNR1 variant cases were matched 1:10 with non-mutant patients by age, gender, and visit year, excluding those with pre-existing hearing loss. The primary endpoint was SNHL, identified using specific ICD-TM codes with a 90% positive predictive value. Medication exposure history was determined via self-report or electronic medical records in the hospital. Cox proportional hazard regression models were used to assess the association between MT-RNR1 variants and hearing loss, adjusting for various covariates. Kaplan-Meier survival curves and log-rank tests compared hearing loss incidence between groups. Results: The mean age of the mtDNA variants group is 32.4 years, with a standard deviation of 19.2 years. The incidence density of hearing loss for the mutation group was 36.42 per 10,000 person-years (95% Confidence Interval [CI], 27.21–47.73), which was higher than the 23.77per 10,000 person-years (95% CI, 21.32–26.42) in the wild-type group (p = 0.0036). Additionally, diabetes mellitus was associated with an increased risk of developing SNHL in individuals with MT-RNR1 variants (adjusted hazard ratio = 1.76 [95% CI, 1.00-3.09], p < 0.05). Conclusion: This study highlights the increased risk of hearing loss in patients carrying MT-RNR1 variants, particularly those with diabetes mellitus. Future research that integrates genetic and clinical data is crucial for developing more precise interventions to monitor and treat hearing loss in this vulnerable population. [ABSTRACT FROM AUTHOR]

Huntington's disease (HD) predominantly affects the brain, causing a mixed movement disorder, cognitive decline and behavioural abnormalities. It also causes a peripheral phenotype involving skeletal muscle. Mitochondrial dysfunction has been reported in tissues of HD models, including skeletal muscle, and lymphoblast and fibroblast cultures from patients with HD. Mutant huntingtin protein (mutHTT) expression can impair mitochondrial quality control and accelerate mitochondrial ageing. Here, we obtained fresh human skeletal muscle, a post-mitotic tissue expressing the mutated HTT allele at physiological levels since birth, and primary cell lines from HTT CAG repeat expansion mutation carriers and matched healthy volunteers to examine whether such a mitochondrial phenotype exists in human HD. Using ultra-deep mitochondrial DNA (mtDNA) sequencing, we showed an accumulation of mtDNA mutations affecting oxidative phosphorylation. Tissue proteomics indicated impairments in mtDNA maintenance with increased mitochondrial biogenesis of less efficient oxidative phosphorylation (lower complex I and IV activity). In full-length mutHTT expressing primary human cell lines, fission-inducing mitochondrial stress resulted in normal mitophagy. In contrast, expression of high levels of N-terminal mutHTT fragments promoted mitochondrial fission and resulted in slower, less dynamic mitophagy. Expression of high levels of mutHTT fragments due to somatic nuclear HTT CAG instability can thus affect mitochondrial network dynamics and mitophagy, leading to pathogenic mtDNA mutations. We show that life-long expression of mutant HTT causes a mitochondrial phenotype indicative of mtDNA instability in fresh post-mitotic human skeletal muscle. Thus, genomic instability may not be limited to nuclear DNA, where it results in somatic expansion of the HTT CAG repeat length in particularly vulnerable cells such as striatal neurons. In addition to efforts targeting the causative mutation, promoting mitochondrial health may be a complementary strategy in treating diseases with DNA instability such as HD. [ABSTRACT FROM AUTHOR]

Background: Peripheral neuropathies in mitochondrial disease are caused by mutations in nuclear genes encoding mitochondrial proteins, or in the mitochondrial genome. Whole exome or genome sequencing enable parallel testing of nuclear and mtDNA genes, and it has significantly advanced the genetic diagnosis of inherited diseases. Despite this, approximately 40% of all Charcot-Marie-Tooth (CMT) cases remain undiagnosed. Methods: The genome-phenome analysis platform (GPAP) in RD-Connect was utilised to create a cohort of 2087 patients with at least one Human Phenotype Ontology (HPO) term suggestive of a peripheral neuropathy, from a total of 10,935 patients. These patients' genetic data were then analysed and searched for variants in known mitochondrial disease genes. Results: A total of 1,379 rare variants were identified, 44 of which were included in this study as either reported pathogenic or likely causative in 42 patients from 36 families. The most common genes found to be likely causative for an autosomal dominant neuropathy were GDAP1 and GARS1. We also detected heterozygous likely pathogenic variants in DNA2, MFN2, DNM2, PDHA1, SDHA, and UCHL1. Biallelic variants in SACS, SPG7, GDAP1, C12orf65, UCHL1, NDUFS6, ETFDH and DARS2 and variants in the mitochondrial DNA (mtDNA)-encoded MT-ATP6 and MT-TK were also causative for mitochondrial CMT. Only 50% of these variants were already reported as solved in GPAP. Conclusion: Variants in mitochondrial disease genes are frequent in patients with inherited peripheral neuropathies. Due to the clinical overlap between mitochondrial disease and CMT, agnostic exome or genome sequencing have better diagnostic yields than targeted gene panels. [ABSTRACT FROM AUTHOR]

Maternally inherited diabetes and deafness (MIDD) is a rare mitochondrial disorder primarily resulting from m.3243A>G mutation. The clinical characteristics of MIDD exhibit significant heterogeneity. Our study aims to delineate these characteristics and determine the potential correlation with m.3243A>G heteroplasmy levels. This retrospective, descriptive study encompassed patients with confirmed m.3243A>G mutation and diabetes mellitus at Seoul National University Hospital. Our cohort comprises 40 patients with MIDD, with a mean age at study enrollment of 33.3±12.9 years and an average % of heteroplasmy of 30.0%± 14.6% in the peripheral blood. The most prevalent comorbidity was hearing loss (90%), followed by albuminuria (61%), seizure (38%), and stroke (33%). We observed a significant negative correlation between % of heteroplasmy and age at diabetes diagnosis. These clinical features can aid in the suspicion of MIDD and further consideration of genetic testing for m.3243A>G mutation. [ABSTRACT FROM AUTHOR]

Background: Sequencing the mitochondrial genome has been increasingly important for the investigation of primary mitochondrial diseases (PMD) and mitochondrial genetics. To overcome the limitations originating from PCR-based mtDNA enrichment, we set out to develop and evaluate a PCR-independent approach in this study, named Pime-Seq (PCR-independent mtDNA enrichment and next generation Sequencing). Results: By using the optimized mtDNA enrichment procedure, the mtDNA reads ratio reached 88.0 ± 7.9% in the sequencing library when applied on human PBMC samples. We found the variants called by Pime-Seq were highly consistent among technical repeats. To evaluate the accuracy and reliability of this method, we compared Pime-Seq with lrPCR based NGS by performing both methods simultaneously on 45 samples, yielding 1677 concordant variants, as well as 146 discordant variants with low-level heteroplasmic fraction, in which Pime-Seq showed higher reliability. Furthermore, we applied Pime-Seq on 4 samples of PMD patients retrospectively, and successfully detected all the pathogenic mtDNA variants. In addition, we performed a prospective study on 192 apparently healthy pregnant women during prenatal screening, in which Pime-Seq identified pathogenic mtDNA variants in 4 samples, providing extra information for better health monitoring in these cases. Conclusions: Pime-Seq can obtain highly enriched mtDNA in a PCR-independent manner for high quality and reliable mtDNA deep-sequencing, which provides us an effective and promising tool for detecting mtDNA variants for both clinical and research purposes. [ABSTRACT FROM AUTHOR]

Growing evidence has demonstrated that peripapillary hyperreflective ovoid mass-like structures (PHOMS) are novel structures rather than a subtype of optic disc drusen. They correspond to the laterally bulging herniation of optic nerve fibers and are believed to be the marker of axoplasmic stasis. PHOMS present in a broad spectrum of diseases, including optic disc drusen, tilted disc syndrome, papilloedema, multiple sclerosis, non-arteritic anterior ischemic optic neuropathy, optic neuritis, Leber hereditary optic neuropathy, and so on. We focus on the multimodal imaging features, pathophysiological mechanisms of PHOMS, and their association with multiple diseases and healthy people in this review to deepen the ophthalmologists' understanding of PHOMS. Additionally, we provide some new directions for future research. [ABSTRACT FROM AUTHOR]

Aim: To assess the presence of mitochondrial (mt) DNA somatic mutations, determine the relationship between clinicopathological characteristics and mutations, and assess the survival outcomes in Malay patients with primary brain tumors. Methods: The study enrolled 54 patients with primary brain tumors. DNA extracted from paired tissue and blood samples was subjected to Sanger sequencing to identify alterations in the entire mtDNA. The associations between clinicopathological characteristics and mutations were evaluated. Cox-regression multivariate analysis was conducted to identify factors significantly associated with survival, and Kaplan-Meier analysis was used to compare the survival of patients with and without mutations. Results: Overall, 29.6% of the patients harbored 19 somatic mutations distributed across 15 loci within the mtDNA. Notably, 36.8% of these mutations were not previously documented in MITOMAP. One newly identified mutation caused a frameshift in the ATPase6 gene, resulting in a premature stop codon. Three mutations were classified as deleterious in the MitImpact2 database. Overall, 1097 mtDNA polymorphisms were identified across 331 different locations. Patients with mutations exhibited significantly shorter survival than patients without mutations. Conclusions: mtDNA mutations negatively affected the survival outcomes of Malaysian patients with primary brain tumors. However, studies with larger samples are needed to confirm the association between mutation burden and survival rates. [ABSTRACT FROM AUTHOR]

Introduction: Rare disorders that are genetically and clinically heterogeneous, such as mitochondrial diseases (MDs), have a challenging diagnosis. Nuclear genes codify most proteins involved in mitochondrial biogenesis, despite all mitochondria having their own DNA. The development of next-generation sequencing (NGS) technologies has revolutionized the understanding of many genes involved in the pathogenesis of MDs. In this new genetic era, using the NGS approach, we aimed to identify the genetic etiology for a suspected MD in a cohort of 450 Portuguese patients. Methods: We examined 450 patients using a combined NGS strategy, starting with the analysis of a targeted mitochondrial panel of 213 nuclear genes, and then proceeding to analyze the whole mitochondrial DNA. Results and Discussion: In this study, we identified disease-related variants in 134 (30%) analyzed patients, 88 with nuclear DNA (nDNA) and 46 with mitochondrial DNA (mtDNA) variants, most of them being pediatric patients (66%), of which 77% were identified in nDNA and 23% in mtDNA. The molecular analysis of this cohort revealed 72 already described pathogenic and 20 novel, probably pathogenic, variants, as well as 62 variants of unknown significance. For this cohort of patients with suspected MDs, the use of a customized gene panel provided a molecular diagnosis in a timely and cost-effective manner. Patients who cannot be diagnosed after this initial approach will be further selected for whole-exome sequencing. Conclusion: As a national laboratory for the study and research of MDs, we demonstrated the power of NGS to achieve a molecular etiology, expanding the mutational spectrum and proposing accurate genetic counseling in this group of heterogeneous diseases without therapeutic options. [ABSTRACT FROM AUTHOR]

A patient with primary CoQ10 deficiency associated with the c.901 C > T (p.R301W) (rs140246430) homozygous missense pathogenic variant in the COQ8A gene, who presented with recurrent status epilepticus, stroke-like lesions, and hypertrophic cardiomyopathy while being followed-up with early-onset autosomal recessive cerebellar ataxia will be reported in this article. A 16-year-old patient who was being followed up at an external center with a diagnosis of ataxia with cerebellar atrophy had been seen 3 different times within a year for status epilepticus. The cerebral MRI showed severe cerebellar atrophy, stroke like lesions, and an inverted double- lactate peak on spectroscopy. Her echocardiography revealed marked left ventricular hypertrophy. Mitochondrial cocktail therapy containing a standard dose of CoQ10 was started, considering mitochondrial disease. The patient died due to cardiomyopathy. Mitochondrial panel analysis revealed the presence of the c.901 C > T (p.R301W) homozygous missense mutation in the COQ8A gene. Primary Coenzyme Q10 deficiency should be considered in patients presenting with autosomal recessive stable-appearing progressive ataxia, emerging attacks of status epilepticus, stroke-like lesions on neuroimaging, and cardiomyopathy. Since there is a case with the same mutation with a similar fatal course in the literature, detection of c.901 C > T (p.R301W) mutation homozygously should be a warning for a severe prognosis and more aggressive treatment should be started without delay with a high dose of CoQ10 instead of the lower doses used in the treatment of mitochondrial disease. [ABSTRACT FROM AUTHOR]

The article explores the potential of circulating cell-free mitochondrial DNA (cf-mtDNA) as a biomarker for cancer detection and management. It discusses the limitations of current diagnostic and treatment options for cancer and the benefits of using cf-mtDNA as a non-invasive and sensitive tumor marker. Various techniques for detecting and analyzing cf-mtDNA are discussed, along with its applications in early diagnosis, tumor burden assessment, treatment design, and prognosis indication. The authors acknowledge the challenges in utilizing cf-mtDNA as a biomarker, including limited understanding of its biology, difficulties in detecting tumor-specific cf-mtDNA, high costs and technical requirements of liquid biopsy techniques, and the need for better strategies to eliminate non-informative sequences. They suggest that further research and technological advancements are necessary to fully harness the potential of cf-mtDNA in cancer management. [Extracted from the article]

Leber's hereditary optic neuropathy (LHON) is one of the hereditary optic neuropathies and is principally caused by three frequent mitochondria deoxyribonucleic acid (DNA) pathogenic variants (m.11778 G>A, m.3460 G>A, and m.14484T>C). These pathogenic variants account for 90% of LHON cases, with rare pathogenic variants accounting for the remaining cases. We report the first Japanese case of LHON with the m.13051 G>A pathogenic variant, which is a rare primary pathogenic variant of LHON. A 24-year-old woman developed subacute visual loss in both eyes over several months. The best corrected visual acuity (BCVA) was 6/120 in her right eye (OD) and 6/7.5 in her left eye (OS). A relative afferent pupillary defect was not detected. Humphrey visual field testing revealed a central scotoma OD and a temporal paracentral scotoma OS. Fundus examination showed the presence of a pale optic disc OD and optic disc swelling with peripapillary microangiopathy OS. Orbital magnetic resonance imaging showed no abnormal findings. As the mitochondrial DNA gene testing demonstrated the m.13051 G>A pathogenic variant, the patient was diagnosed with LHON. Subsequently, her BCVA worsened to 6/600 in each eye, followed by a nearly plateau-like progression thereafter. This mutation has been primarily reported in Europe but has not yet been confirmed in the Asian region. This case also indicates the importance of examining the whole mitochondrial DNA gene for pathogenic variants in cases where one of the three major pathogenic variants has not been not detected. [ABSTRACT FROM AUTHOR]

This article discusses the effects of idebenone treatment in a patient with DNAJC30-associated Leigh Syndrome. Leigh Syndrome is a neurological disorder caused by disruptions in energy balance, often resulting in symptoms such as optic neuropathy and limb dystonia. Idebenone is a drug used to treat mitochondrial diseases, but its effectiveness in DNAJC30-associated Leigh Syndrome is uncertain. The article presents a case study of a patient who did not show improvement with idebenone treatment and suggests that further studies are needed to evaluate its effectiveness in this specific syndrome. [Extracted from the article]

Photobiomodulation (PBM) is a type of phototherapy that employs light-emitting diodes (LEDs) or low-power lasers to selectively administer specific wavelengths of visible light, ranging from 500 to 1000 nm, including near-infrared (NIR) wavelengths. LEDs are advantageous compared to lasers due to their ability to treat large areas at a lower cost, lack of tissue damage potential in humans, and reduced risk of eye-related accidents. The ophthalmology community has recently taken interest in PBM as a promising novel approach for managing various retinal conditions such as age-related macular degeneration, retinopathy of prematurity, retinitis pigmentosa, diabetic retinopathy, Leber's hereditary optic neuropathy, amblyopia, methanol-induced retinal damage, and potentially others. This review critically assesses the existing body of research on PBM applications in the retina, focusing on elucidating the underlying mechanisms of action and evaluating the clinical outcomes associated with this therapeutic modality. [ABSTRACT FROM AUTHOR]

Introduction: Leber hereditary optic neuropathy (LHON) is a maternally inherited, acute or subacute, optic neuropathy. The typical symptoms include reduced visual acuity and central scotoma. Despite the presence of deep central scotoma, some patients with LHON are able to perform daily activities. This study aimed to investigate the correlation between the residual visual field and visual acuity, critical flicker frequency, and fixation ellipse in patients with chronic LHON. Methods: Residual visual function (defined as sensitivity points where patients sensed the size V stimulus) of both eyes was evaluated in 10 patients with LHON carrying the m.11778 mitochondrial DNA mutation and with median age of onset and disease duration of 29 and 16.5 years, respectively. The central visual field was measured as static perimetry using the Humphrey visual field testing 30-2 program with the size III or V stimulus. Moreover, best-corrected visual acuity, critical flicker frequency, and the correlation between fixation ellipse and residual central visual fields were determined. The analysis was performed through a linear mixed-effects model. Results: The residual visual sensitivity in the inferior nasal visual field was significantly correlated with the logMAR (p < 0.05). The fixation ellipse fell within the residual visual field region with higher sensitivity. Conclusions: Patients with chronic LHON tended to retain the sensitivity detectable with the size V stimulus at the central inferior nasal visual field regions, where the fixation ellipse fell. Visual acuity, which influences daily activity, was spatially correlated with residual visual sensitivity. [ABSTRACT FROM AUTHOR]

Mitochondria undergo morphological changes during spermatogenesis in some animals. The mechanism and role of mitochondrial morphology regulation, however, remain somewhat unclear. In this study, we analyzed the molecular characteristics, expression dynamics and subcellular localization of optic atrophy protein 1 (OPA1), a mitochondrial fusion and cristae maintenance-related protein, to reveal the possible regulatory mechanisms underlying mitochondrial morphology in Phascolosoma esculenta spermiogenesis. The full-length cDNA of the P. esculenta opa1 gene (Pe-opa1) is 3 743 bp in length and encodes 975 amino acids. The Pe-OPA1 protein is highly conservative and includes a transmembrane domain, a GTPase domain, two helical bundle domains, and a lipid-interacting stalk. Gene and protein expression was higher in the coelomic fluid (a site of spermatid development) of male P. esculenta and increased first and then decreased from March to December. Moreover, their expression during the breeding stage was significantly higher than during the non-breeding stage, suggesting that Pe-OPA1 is involved in P. esculenta reproduction. The Pe-OPA1 protein was more abundant in components consisting of many spermatids than in components without, indicating that Pe-OPA1 mainly plays a role in the spermatid in coelomic fluid. Moreover, Pe-OPA1 was mainly detected in the spermatid mitochondria. Immunofluorescence experiments showed that the Pe-OPA1 are constitutively expressed and co-localized with mitochondria during spermiogenesis, suggesting its involvement in P. esculenta spermiogenesis. These results provide evidence for Pe-OPA1's involvement in the regulation of mitochondrial morphology during spermiogenesis. [ABSTRACT FROM AUTHOR]

Purpose: Peripapillary hyperreflective ovoid mass-like structures (PHOMS) represent an optical coherence tomography (OCT) finding that has been characterized in different forms of pseudopapilledema. The aim of this study was to investigate the prevalence of PHOMS in patients affected by acute LHON using structural OCT, and to provide a detailed description of these findings. Methods: Patients with a clinical and molecularly confirmed diagnosis of acute LHON (visual loss having occurred less than 6 months) were enrolled from the neuro-ophthalmology clinic at San Raffaele Scientific Institute. Patients had a complete ophthalmologic evaluation, including imaging with structural OCT. Results: Our analysis included 16 patients (21 eyes—8 males and 8 females) with acute LHON. Structural OCT exhibited PHOMS in 12 eyes from 9 patients with a prevalence rate of 57.1%. In a subsequent topographical assessment in the peripapillary area, the most common location of PHOMS was the temporal region (12 out of 12 eyes), while the nasal region was affected in 2 eyes (16.7%). Considering the 12 eyes with PHOMS, mean ± SD temporal peripapillary RNFL thickness was 87.5 ± 28.4 microns. The temporal peripapillary RNFL thickness was significantly lower in eyes without PHOMS (63.7 ± 32.2 microns; P = 0.40). At the 12-month follow-up visit, PHOMS disappeared in 10 out of 12 eyes. Conclusions: Acute LHON eyes have PHOMS which are mainly confined to the temporal peripapillary sector. PHOMS may represent swelled retinal fibers that have herniated or are in stasis. [ABSTRACT FROM AUTHOR]

Background: Leber Hereditary Optic Neuropathy (LHON) is the most common inherited mitochondrial disease characterized by bilateral, painless, subacute visual loss with a peak age of onset in the second to third decade. Historically, LHON was thought to be exclusively maternally inherited due to mutations in mitochondrial DNA (mtDNA); however, recent studies have identified an autosomal recessive form of LHON (arLHON) caused by point mutations in the nuclear gene, DNAJC30. Case Presentations: In this study, we report the cases of three Eastern European individuals presenting with bilateral painless visual loss, one of whom was also exhibiting motor symptoms. After a several-year-long diagnostic journey, all three patients were found to carry the homozygous c.152A>G (p.Tyr51Cys) mutation in DNAJC30. This has been identified as the most common arLHON pathogenic variant and has been shown to exhibit a significant founder eect amongst Eastern European individuals. Conclusion: This finding adds to the growing cohort of patients with arLHON and demonstrates the importance of DNAJC30 screening in patients with molecularly undiagnosed LHON, particularly in Eastern European individuals. It is of heightened translational significance as patients diagnosed with arLHON exhibit a better prognosis and response to therapeutic treatment with the co-enzyme Q10 analog idebenone. [ABSTRACT FROM AUTHOR]

• Mutations in mitochondrial t-RNA are associated with a complex group of diseases characterized by different clinical presentations and involvement of various organs. The affected tissues are those with higher energy requirement, such as the skeletal muscle, where a defect in the proteins involved in the respiratory chain determines significant impairment of tissue function. Consequently, myopathy is frequently present. • A history of exercise-induced fatigability and swelling of the masseter muscles after prolonged chewing, associated metabolic acidosis with hyperlactatemia, should suggest the presence of a pathogenic variant in the MT-TP gene. • Cardiac involvement may be present in patients with MT-TP mutations, therefore cardiac function should be closely monitored throughout their life. A 16-year-old boy was evaluated for a history of exercise-induced fatigability associated with nausea even after minimal effort, lower limbs muscle hypotrophy, and swelling of the masseter muscles after chewing. Laboratory tests were remarkable for hyperlactatemia and metabolic acidosis after short physical activity. The muscle biopsy showed non-specific mitochondrial alterations and an increase in intrafibral lipids. Biochemical analysis showed reduced activity of the respiratory chain complexes. Mitochondrial DNA sequencing revealed the presence of a homoplasmic variant m.15992A> T in the MT-TP gene, coding for the mt-tRNAPro in the patient, in his mother and in his brother. Pathogenic or likely pathogenic variants in MT-TP gene are rare. They are responsible for different clinical presentation, almost ever involving the muscle tissue. We report the first family with exercise-induced muscle weakness and swelling of the chewing muscles due to m.15992A> T variant in absence of J1c10 haplogroup, confirming its pathogenicity. [ABSTRACT FROM AUTHOR]

Cardiomyopathies are major causes of heart failure. Chagas disease (CD) is caused by the parasite Trypanosoma cruzi, and it is endemic in Central and South America. Thirty percent of cases evolve into chronic chagas cardiomyopathy (CCC), which has worse prognosis as compared with other cardiomyopathies. In vivo bioenergetic analysis and ex vivo proteomic analysis of myocardial tissues highlighted worse mitochondrial dysfunction in CCC, and previous studies identified nuclear-encoded mitochondrial gene variants segregating with CCC. Here, we assessed the role of the mitochondrial genome through mtDNA copy number variations and mtDNA haplotyping and sequencing from heart or blood tissues of severe, moderate CCC and asymptomatic/indeterminate Chagas disease as well as healthy controls as an attempt to help decipher mitochondrial-intrinsic genetic involvement in Chagas disease development. We have found that the mtDNA copy number was significantly lower in CCC than in heart tissue from healthy individuals, while blood mtDNA content was similar among asymptomatic Chagas disease, moderate, and severe CCC patients. An MtDNA haplogrouping study has indicated that African haplogroups were over represented in the Chagas subject groups in comparison with healthy Brazilian individuals. The European lineage is associated with protection against cardiomyopathy and the macro haplogroup H is associated with increased risk towards CCC. Using mitochondria DNA sequencing, 84 mtDNA-encoded protein sequence pathogenic variants were associated with CCC. Among them, two variants were associated to left ventricular non-compaction and two to hypertrophic cardiomyopathy. The finding that mitochondrial protein-coding SNPs and mitochondrial haplogroups associate with risk of evolving to CCC is consistent with a key role of mitochondrial DNA in the development of chronic chagas disease cardiomyopathy. [ABSTRACT FROM AUTHOR]

Background: Breast cancer is, despite screening, not always detected early enough and is together with other tumor types known to shed genetic information in circulation. Unlike single-copy nuclear DNA, mitochondrial DNA (mtDNA) copies range from 100s to 10,000s per cell, thus providing a potentially alternative to identify potential missing cancer information in circulation at an early stage. Methods: To characterize mitochondrial mutation landscapes in breast cancer, whole mtDNA sequencing and bioinformatics analyses were performed on 86 breast cancer biopsies and 50 available matched baseline cancer-free whole blood samples from the same individuals, selected from a cohort of middle-aged women in Sweden. To determine whether the mutations can be detected in blood plasma prior to cancer diagnosis, we further designed a nested case-control study (n = 663) and validated the shortlisted mutations using droplet digital PCR. Results: We detected different mutation landscapes between biopsies and matched whole blood samples. Compared to whole blood samples, mtDNA from biopsies had higher heteroplasmic mutations in the D-loop region (P = 0.02), RNR2 (P = 0.005), COX1 (P = 0.037) and CYTB (P = 0.006). Furthermore, the germline mtDNA mutations had higher heteroplasmy level than the lost (P = 0.002) and de novo mutations (P = 0.04). The nonsynonymous to synonymous substitution ratio (dN/dS) was higher for the heteroplasmic mutations (P = 7.25 × 10−12) than that for the homoplasmic mutations, but the de novo (P = 0.06) and lost mutations (P = 0.03) had lower dN/dS than the germline mutations. Interestingly, we found that the critical regions for mitochondrial transcription: MT-HSP1 (odds ratio [OR]: 21.41), MT-TFH (OR: 7.70) and MT-TAS2 (OR: 3.62), had significantly higher heteroplasmic mutations than the rest of the D-loop sub-regions. Finally, we found that the presence of mt.16093T > C mutation increases 67% risk of developing breast cancer. Conclusions: Our findings show that mitochondrial genetic landscape changes during cancer pathogenesis and positive selection of mtDNA heteroplasmic mutations in breast cancer. Most importantly, the mitochondrial mutations identified in biopsies can be traced back in matched plasma samples and could potentially be used as early breast cancer diagnostic biomarkers. [ABSTRACT FROM AUTHOR]

A case of a patient with the Alström syndrome (AS) that was misdiagnosed as Leber's hereditary optic neuropathy or retinitis pigmentosa for 13 years is presented. AS is a rare genetic disorder caused by mutations in the ALMS1 gene. AS may lead to abnormal ciliary formation and function. AS affects metabolism, and symptomatology includes type 2 diabetes mellitus (T2DM), obesity, hypogonadism and gynecomastia in males, progressive bilateral sensorineural hearing loss, cardiomyopathy, nonalcoholic fatty liver disease (NAFLD), cirrhosis, and chronic progressive kidney disease. The onset of the above symptoms may vary significantly. The ophthalmic manifestation is early onset cone-rod dystrophy that starts as progressive vision loss, photophobia, and nystagmus in the first months of life. An accurate diagnosis may enable specialists to facilitate a significantly positive effect in the everyday life of a patient. Genetic counseling may also be recommended for these patients. Diagnosis was confirmed by DNA testing, thus highlighting its necessity in everyday practice. [ABSTRACT FROM AUTHOR]

A letter to the editor of Acta Neuropathologica Communications discusses the potential use of nicotinamide (vitamin B3) in the treatment of optic neuropathies. The authors reference previous studies that have shown the protective effects of nicotinamide on retinal ganglion cells in animal models of glaucoma and report their own findings of nicotinamide deficiency in individuals with Leber's Hereditary Optic Neuropathy (LHON) and Dominant Optic Atrophy (DOA). They also mention a clinical trial that has been launched to test the safety and efficacy of oral nicotinamide in individuals with DOA. The authors suggest that nicotinamide may have therapeutic potential for various forms of optic neuropathies and call for further research in this area. [Extracted from the article]

Mitochondria are essential organelles for cellular metabolism and physiology in eukaryotic cells. Human mitochondria have their own genome (mtDNA), which is maternally inherited with 37 genes, encoding 13 polypeptides for oxidative phosphorylation, and 22 tRNAs and 2 rRNAs for translation. mtDNA mutations are associated with a wide spectrum of degenerative and neuromuscular diseases. However, the pathophysiology of mitochondrial diseases, especially for threshold effect and tissue specificity, is not well understood and there is no effective treatment for these disorders. Especially, the lack of appropriate cell and animal disease models has been significant obstacles for deep elucidating the pathophysiology of maternally transmitted diseases and developing the effective therapy approach. The use of human induced pluripotent stem cells (iPSCs) derived from patients to obtain terminally differentiated specific lineages such as inner ear hair cells is a revolutionary approach to deeply understand pathogenic mechanisms and develop the therapeutic interventions of mitochondrial disorders. Here, we review the recent advances in patients-derived iPSCs as ex vivo models for mitochondrial diseases. Those patients-derived iPSCs have been differentiated into specific targeting cells such as retinal ganglion cells and eventually organoid for the disease modeling. These disease models have advanced our understanding of the pathophysiology of maternally inherited diseases and stepped toward therapeutic interventions for these diseases. [ABSTRACT FROM AUTHOR]

Introduction: Limited diagnostics are available for inherited neuromuscular diseases (NMD) in South Africa and (excluding muscle disease) are mainly aimed at the most frequent genes underlying genetic neuropathy (GN) and spastic ataxias in Europeans. In this study, we used next-generation sequencing to screen 61 probands with GN, hereditary spastic paraplegia (HSP), and spastic ataxias for a genetic diagnosis. Methods: After identifying four GN probands with PMP22 duplication and one spastic ataxia proband with SCA1, the remaining probands underwent whole exome (n = 26) or genome sequencing (n = 30). The curation of coding/splice region variants using gene panels was guided by allele frequencies from internal African-ancestry control genomes (n = 537) and the Clinical Genome Resource's Sequence Variant Interpretation guidelines. Results: Of 32 GN probands, 50% had African-genetic ancestry, and 44% were solved: PMP22 (n = 4); MFN2 (n = 3); one each of MORC2, ATP1A1, ADPRHL2, GJB1, GAN, MPZ, and ATM. Of 29 HSP probands (six with predominant ataxia), 66% had African-genetic ancestry, and 48% were solved: SPG11 (n = 3); KIF1A (n = 2); and one each of SPAST, ATL1, SPG7, PCYT2, PSEN1, ATXN1, ALDH18A1, CYP7B1, and RFT1. Structural variants in SPAST, SPG11, SPG7, MFN2, MPZ, KIF5A, and GJB1 were excluded by computational prediction and manual visualisation. Discussion: In this preliminary cohort screening panel of disease genes using WES/WGS data, we solved ~50% of cases, which is similar to diagnostic yields reported for global cohorts. However, the mutational profile among South Africans with GN and HSP differs substantially from that in the Global North. [ABSTRACT FROM AUTHOR]

We read with great interest the recent publication by Rocatcher and colleagues[1] entitled 'The top 10 most frequently involved genes in hereditary optic neuropathies in 2186 probands', reporting on the experience of a national diagnostic centre for hereditary optic neuropathies (HON) in France. This flexible approach enlarges the number of genes screened, compared with the fixed number of 87 genes included in the custom targeted gene panel reported by Rocatcher I et al i .[1] Therefore, we found pathogenic variants in 30 genes, of which 18 were in single families (8.4%), whereas in the French cohort, only 21 genes were found to carry pathogenic variants, with seven singleton cases (1.5%). This is currently the standard algorithm followed by I in silico i panel analysis, prioritizing variants in known HON genes, to eventually discover new disease genes. Thus, the top 10 genes are consolidated by the contribution of the Italian cohort, with I OPA1 i , I WFS1 i and I ACO2 i accounting for 76% of diagnosed HON, due to a nuclear gene defect. [Extracted from the article]

Introduction: Mitochondrial disease is a spectrum of debilitating disorders caused by mutations in the mitochondrial DNA (mtDNA) or nuclear DNA that compromises the respiratory chain. Mitochondrial 3243A>G (m.3243 A>G) is the most common mutation showing great heterogeneity in phenotype. Previous studies have indicated that NADH: ubiquinone oxidoreductase (complex I) deficiency accompanied by a decreased nicotinamide adenine dinucleotide (NAD+)/reduced NAD+ (NADH) ratio may play a pivotal role in the pathogenesis of m.3243A>G mutation. Methods: To evaluate the potential effects of strategies targeting the imbalanced NAD+/NADH ratio in m.3243A>G mutation, we treated fibroblasts derived from patients with the m.3243 A>G mutation using nicotinamide riboside (NR) or mitochondria-targeted H2O-forming NADH oxidase (mitoLbNOX). Results: M.3243 A>G fibroblasts showed a significant reduction in complex I core subunit 6, complex I enzymatic activity, complex I-dependent oxygen consumption rate (OCR), and adenosine triphosphate (ATP) production compared to the controls. The NAD+/NADH ratio was also significantly reduced in m.3243 A>G fibroblasts, and, using fluorescence lifetime imaging microscopy, we also found that the NADH level was elevated in m.3243 A>G fibroblasts. After NR treatment, the NAD+/NADH ratio, complex I-dependent OCR, and ATP levels increased, whereas NADH levels remained unchanged. More excitingly, after treatment with mitoLbNOX, the NAD+/NADH ratio, complex I-independent OCR, and ATP levels increased more pronouncedly compared with the NR treatment group, accompanied by significantly reduced NADH levels. Discussion: The present study suggests that compared with repletion of NAD+ alone, the combination of this therapeutic modality with alleviation of NADH overload may amplify the treatment effect of restoring NAD+/NADH balance in m.3243A>G fibroblasts. [ABSTRACT FROM AUTHOR]

Multiple myeloma (MM) is the second most common hematological cancer that has no cure. Although currently there are several novel drugs, most MM patients experience drug resistance and disease relapse. The results of previous studies suggest that aberrant mitochondrial function may contribute to tumor progression and drug resistance. Mitochondrial DNA mutations and metabolic reprogramming have been reported in MM patients. Several preclinical and clinical studies have shown encouraging results of mitochondria-targeting therapy in MM patients. In this review, we have summarized our current understanding of mitochondrial biology in MM. More importantly, we have reviewed mitochondrial targeting strategies in MM treatment. [ABSTRACT FROM AUTHOR]

Background: Leber's hereditary optic neuropathy (LHON) is a maternally inherited eye disease due to mutations in mitochondrial DNA. However, there is no effective treatment for this disease. LHON-linked ND6 14484T > C (p.M64V) mutation caused complex I deficiency, diminished ATP production, increased production of reactive oxygen species (ROS), elevated apoptosis, and impaired mitophagy. Here, we investigated if the allotopic expression of human mitochondrial ND6 transgene corrected the mitochondrial dysfunctions due to LHON-associated m.14484T > C mutation. Methods: Nucleus-versions of ND6 was generated by changing 6 non-universal codons with universal codons and added to mitochondrial targeting sequence of COX8. Stable transfectants were generated by transferring human ND6 cDNA expressed in a pCDH-puro vector into mutant cybrids carrying the m.14484T > C mutation and control cybrids. The effect of allotopic expression of ND6 on oxidative phosphorylation (OXPHOS) was evaluated using Blue Native gel electrophoresis and extracellular flux analyzer. Assessment of ROS production in cell lines was performed by flow cytometry with MitoSOX Red reagent. Analyses for apoptosis and mitophagy were undertaken via flow cytometry, TUNEL and immunofluorescence assays. Results: The transfer of human ND6 into the cybrids carrying the m.14484T > C mutation raised the levels of ND6, ND1 and ND4L but did not change the levels of other mitochondrial proteins. The overexpression of ND6 led to 20~23% increases in the assembly and activity of complex I, and ~ 53% and ~ 33% increases in the levels of mitochondrial ATP and ΔΨm in the mutant cybrids bearing m.14484T > C mutation. Furthermore, mutant cybrids with overexpression of ND6 exhibited marked reductions in the levels of mitochondrial ROS. Strikingly, ND6 overexpression markedly inhibited the apoptosis process and restored impaired mitophagy in the cells carrying m.14484T > C mutation. However, overexpression of ND6 did not affect the ND6 level and mitochondrial functions in the wild-type cybrids, indicating that this ND6 level appeared to be the maximum threshold level to maintain the normal cell function. Conclusion: We demonstrated that allotopic expression of nucleus-versions of ND6 restored complex I, apoptosis and mitophagy deficiencies caused by the m.14484T > C mutation. The restoration of m.14484T > C mutation-induced mitochondrial dysfunctions by overexpression of ND6 is a step toward therapeutic interventions for LHON and mitochondrial diseases. [ABSTRACT FROM AUTHOR]

This retrospective case series study reported leptomeningeal interfoliar enhancement revealed by a newer magnetic resonance imaging (MRI) technique - vessel wall MRI based on a black blood 3 dimensional (D) T1-weighted sequence in 6 Susac's syndrome patients. Overall, IIH patients had a higher prevalence of anaemia (22.8%) compared with non-IIH neuro-ophthalmology patients (10.6%). In this prospective study 123 consecutive idiopathic intracranial hypertension (IIH) patients were recruited from neuro-ophthalmology clinics and matched by age and sex to 113 consecutive control patients attending neuro-ophthalmology clinics with diagnoses other than IIH. Among them, 14 patients (20.6%) were < 3 years, 27 patients (39.7%) were between 3-9 years, and 27 patients (39.7%) were between 9-12 years. [Extracted from the article]

While normal human liver is thought to be generally quiescent, clonal hepatocyte expansions have been observed, though neither their cellular source nor their expansion dynamics have been determined. Knowing the hepatocyte cell of origin, and their subsequent dynamics and trajectory within the human liver will provide an important basis to understand disease-associated dysregulation. Herein, we use in vivo lineage tracing and methylation sequence analysis to demonstrate normal human hepatocyte ancestry. We exploit next-generation mitochondrial sequencing to determine hepatocyte clonal expansion dynamics across spatially distinct areas of laser-captured, microdissected, clones, in tandem with computational modelling in morphologically normal human liver. Hepatocyte clones and rare SOX9+ hepatocyte progenitors commonly associate with portal tracts and we present evidence that clones can lineage-trace with cholangiocytes, indicating the presence of a bipotential common ancestor at this niche. Within clones, we demonstrate methylation CpG sequence diversity patterns indicative of periportal not pericentral ancestral origins, indicating a portal to central vein expansion trajectory. Using spatial analysis of mitochondrial DNA variants by next-generation sequencing coupled with mathematical modelling and Bayesian inference across the portal-central axis, we demonstrate that patterns of mitochondrial DNA variants reveal large numbers of spatially restricted mutations in conjunction with limited numbers of clonal mutations. These datasets support the existence of a periportal progenitor niche and indicate that clonal patches exhibit punctuated but slow growth, then quiesce, likely due to acute environmental stimuli. These findings crucially contribute to our understanding of hepatocyte dynamics in the normal human liver. The liver is mainly composed of hepatocytes, but we know little regarding the source of these cells or how they multiply over time within the disease-free human liver. In this study, we determine a source of new hepatocytes by combining many different lab-based methods and computational predictions to show that hepatocytes share a common cell of origin with bile ducts. Both our experimental and computational data also demonstrate hepatocyte clones are likely to expand in slow waves across the liver in a specific trajectory, but often lie dormant for many years. These data show for the first time the expansion dynamics of hepatocytes in normal liver and their cell of origin enabling the accurate measurment of changes to their dynamics that may lead to liver disease. These findings are important for researchers determining cancer risk in human liver. [Display omitted] • Hepatocyte clonal expansions emanate from periportal origins in normal human livers. • Clonal hepatocyte expansions are more numerous with age. • Biliary epithelium and hepatocytes share a common somatic ancestor. • Clonal expansion in normal human liver is slow and/or punctuated. [ABSTRACT FROM AUTHOR]

Leber hereditary optic neuropathy (LHON) is a primary inherited neurodegenerative disorder of the optic nerve. It has been ascribed to variants in the mitochondrial genome, mainly the m.3460G>A, m.11778G>A and m.14484T>C mutations in ND1 , ND4 and ND6 , respectively. Nonetheless, inconclusive molecular diagnosis is not uncommon. Recently, biallelic mutations in the NDUFS2 , DNAJC30 , MCAT and NDUFA12 nuclear genes have been identified in unresolved LHON cases, identifying an autosomal recessive LHON (arLHON, OMIM:619382). The clinical presentation of arLHON copies that of typical LHON due to mtDNA mutations (mtLHON), with an acute phase of sudden and severe vision loss, telangiectatic and tortuous vessels around the optic nerve and swelling of the retinal nerve fibre layer. This is followed by a chronic phase of retinal nerve fibre layer loss, but eventually affected individuals recover partial or full visual acuity. Idebenone treatment significantly improved vision recovery in DNAJC30 -associated patients. As for mtLHON, arLHON predominantly affected male compared with female carriers. The discovery of arLHON cases breaks with the dogma of exclusive maternal inheritance. It defines a new neuro-ophthalmo-genetic paradigm, which should be considered in individuals manifesting a LHON phenotype but with an inconclusive molecular diagnosis. NDUFS2 , DNAJC30 , MCAT and NDUFA12 should be investigated in these individuals, knowing that other arLHON genes might exist. [ABSTRACT FROM AUTHOR]

How do carriers of pathogenic mitochondrial DNA (mtDNA) respond to ovarian stimulation? A single-centre, retrospective study conducted between January 2006 and July 2021 in France. Ovarian reserve markers and ovarian stimulation cycle outcomes were compared for couples undergoing preimplantation genetic testing (PGT) for maternally inherited mtDNA disease (n = 18) (mtDNA-PGT group) with a matched-control group of patients undergoing PGT for male indications (n = 96). The PGT outcomes for the mtDNA-PGT group and the follow-up of these patients in case of unsuccessful PGT was also reported. For carriers of pathogenic mtDNA, parameters of ovarian response to FSH and ovarian stimulation cycle outcomes were not different from those of matched-control ovarian stimulation cycles. The carriers of pathogenic mtDNA needed a longer ovarian stimulation and higher dose of gonadotrophins. Three patients (16.7%) obtained a live birth after the PGT process, and eight patients (44.4%) achieved parenthood through alternative methods: oocyte donation (n = 4), natural conception with prenatal diagnosis (n = 2) and adoption (n = 2). To the best of our knowledge, this is the first study of women carrying a mtDNA variant who have undergone a PGT for monogenic (single gene defects) procedure. It is one of the possible options to obtain a healthy baby without observing an impairment in ovarian response to stimulation. [ABSTRACT FROM AUTHOR]

Background and purpose: Mitochondrial diseases (MDs) are heterogeneous disorders caused by mutations in nuclear DNA (nDNA) or mitochondrial DNA (mtDNA) associated with specific syndromes. However, especially in childhood, patients often display heterogeneity. Several reports on the biochemical and molecular profiles in children have been published, but studies tend not to differentiate between mtDNA‐ and nDNA‐associated diseases, and focus is often on a specific phenotype. Thus, large cohort studies specifically focusing on mtDNA defects in the pediatric population are lacking. Methods: We reviewed the clinical, metabolic, biochemical, and neuroimaging data of 150 patients with MDs due to mtDNA alterations collected at our neurological institute over the past 20 years. Results: mtDNA impairment is less frequent than nDNA impairment in pediatric MDs. Ocular involvement is extremely frequent in our cohort, as is classical Leber hereditary optic neuropathy, especially with onset before 12 years of age. Extraneurological manifestations and isolated myopathy appear to be rare, unlike adult phenotypes. Deep gray matter involvement, early disease onset, and specific phenotypes, such as Pearson syndrome and Leigh syndrome, represent unfavorable prognostic factors. Phenotypes related to single large scale mtDNA deletions appear to be very frequent in the pediatric population. Furthermore, we report for the first time an mtDNA pathogenic variant associated with cavitating leukodystrophy. Conclusions: We report on a large cohort of pediatric patients with mtDNA defects, adding new data on the phenotypical characterization of mtDNA defects and suggestions for diagnostic workup and therapeutic approach. [ABSTRACT FROM AUTHOR]

Biallelic mutations in PINK1 / PRKN cause recessive Parkinson's disease. Given the established role of PINK1/Parkin in regulating mitochondrial dynamics, we explored mitochondrial DNA integrity and inflammation as disease modifiers in carriers of mutations in these genes. Mitochondrial DNA integrity was investigated in a large collection of biallelic (n = 84) and monoallelic (n = 170) carriers of PINK1 / PRKN mutations, idiopathic Parkinson's disease patients (n = 67) and controls (n = 90). In addition, we studied global gene expression and serum cytokine levels in a subset. Affected and unaffected PINK1 / PRKN monoallelic mutation carriers can be distinguished by heteroplasmic mitochondrial DNA variant load (area under the curve = 0.83, CI 0.74–0.93). Biallelic PINK1 / PRKN mutation carriers harbour more heteroplasmic mitochondrial DNA variants in blood (P = 0.0006, Z = 3.63) compared to monoallelic mutation carriers. This enrichment was confirmed in induced pluripotent stem cell-derived (controls, n = 3; biallelic PRKN mutation carriers, n = 4) and post-mortem (control, n = 1; biallelic PRKN mutation carrier, n = 1) midbrain neurons. Last, the heteroplasmic mitochondrial DNA variant load correlated with IL6 levels in PINK1 / PRKN mutation carriers (r = 0.57, P = 0.0074). PINK1 / PRKN mutations predispose individuals to mitochondrial DNA variant accumulation in a dose- and disease-dependent manner. [ABSTRACT FROM AUTHOR]

Although optic disc cupping is mostly seen in glaucoma patients, it can occur in non-glaucomatous optic neuropathies (NGON). The characteristics of NGON are cupping toxic optic neuropathies, optic neuritis, compressive ischemia, and hereditary nature. The basic components of optic disc cupping are prelaminar and laminar. Prelaminar thinning, which seemed to be non-specific, occurs in all types of retinal ganglion cell axon loss; such as compressive, ischemic, and inflammatory events; glaucoma; and aging. This form of cupping is usually shallow, with less excavation of the optic disc. Laminar type of cupping which is a clinically profound type of cupping, may damage peripapillary scleral and lamina cribrosa. Sometimes experienced clinicians cannot clearly distinguish glaucomatous from non-glaucomatous cupping. The non-glaucomatous optic neuropathy has more neuroretinal rim pallor with less excavation of the disc than in glaucoma. It also involves central visual acuity and color vision in primary levels with visual field defects aligned vertically and respecting the midline. Evaluation of the patient's medical records, disease presentation, ocular function, and examination are also crucial. Secondary examinations, including visual field examination and optical coherence tomography (OCT) or neuroimaging, facilitate the disease's differentiation. This review presents the methods of examining a patient with an increased cup-to-disc ratio. [ABSTRACT FROM AUTHOR]

Biallelic pathogenic variants in I DNAJC30 i have been reported in approximately 80 patients with recessively inherited Leber Hereditary Optic Neuropathy (LHONAR, MIM # 619,382) and in 6 individuals with Leigh syndrome (LS, MIM # 256,000) [[2]]. It is possible that the heterozygous change in I NDUFA9 i triggers phenotype expression or it is part of a larger set of still elusive genetic or not genetic variants influencing penetrance of the I DNAJC30 i -related disorders. The I DNAJC30 i -associated "LHON phenotype" is clinically indistinguishable from the classical mitochondrial DNA (mtDNA)-associated LHON, and it is characterized by similar hallmarks (incomplete penetrance, male predominance and significant responsiveness to idebenone) [[4]]. [Extracted from the article]

Maternally inherited diabetes and deafness (MIDD) syndrome refers to a rarely diagnosed disorder caused by pathogenic variants in mtDNA. It was first identified in 1992 and, to date, is considered underdiagnosed because of misclassification to type 1 or type 2 diabetes mellitus. MIDD reflects a multisystem metabolic syndrome commonly resulting in insulin-requiring diabetes and sensorineural deafness but can also lead to a broad range of other manifestations. The spectrum of pathology differs among individuals, likely because of varied degrees of heteroplasmy associated with mtDNA. Heteroplasmy also creates diagnostic difficulties, with a high index of suspicion required to diagnose MIDD in some cases. Here, we review a patient with MIDD who presented with an atypical clinical diabetes picture, additionally documenting his pedigree. To our knowledge, this is the first Cypriot reported with MIDD. [ABSTRACT FROM AUTHOR]

STUDY QUESTION Does mitochondrial deficiency affect human embryonic preimplantation development? SUMMARY ANSWER The presence of a pathogenic mitochondrial variant triggers changes in the gene expression of preimplantation human embryos, compromising their development, cell differentiation, and survival. WHAT IS KNOWN ALREADY Quantitative and qualitative anomalies of mitochondrial DNA (mtDNA) are reportedly associated with impaired human embryonic development, but the underlying mechanisms remain unexplained. STUDY DESIGN, SIZE, DURATION Taking advantage of the preimplantation genetic testing for mitochondrial disorders in at-risk couples, we have compared gene expression of 9 human embryos carrying pathogenic variants in either mtDNA genes or nuclear genes encoding mitochondrial protein to 33 age-matched control embryos. PARTICIPANTS/MATERIALS, SETTING, METHODS Single-embryo transcriptomic analysis was performed on whole human blastocyst embryos donated to research. MAIN RESULTS AND THE ROLE OF CHANCE Specific pathogenic mitochondrial variants downregulate gene expression in preimplantation human embryos [566 genes in oxidative phosphorylation (OXPHOS)-deficient embryos], impacting transcriptional regulators, differentiation factors, and nuclear genes encoding mitochondrial proteins. These changes in gene expression primarily alter OXPHOS and cell survival pathways. LIMITATIONS, REASONS FOR CAUTION The number of OXPHOS-deficient embryos available for the study was limited owing to the rarity of this material. However, the molecular signature shared by all these embryos supports the relevance of the findings. WIDER IMPLICATIONS OF THE FINDINGS While identification of reliable markers of normal embryonic development is urgently needed in ART, our study prompts us to consider under-expression of the targeted genes reported here, as predictive biomarkers of mitochondrial dysfunction during preimplantation development. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the 'Association Française contre les Myopathies (AFM-Téléthon)' and the 'La Fondation Maladies Rares'. No competing interests to declare. TRIAL REGISTRATION NUMBER N/A. [ABSTRACT FROM AUTHOR]

• Somatic mutations in nuclear and/or mitochondrial DNA allow for lineage tracing in humans. • Tracing somatic mutations in embryonic blood has identified novel developmental relationships. • Mitochondrial mutational analysis can be combined with multiomic approaches to characterize adult human hematopoiesis. Lineage tracing using fluorescent proteins, genetic barcodes, and various other strategies has provided critical insights into the dynamics of both fetal and adult hematopoiesis in model organisms. However, these technologies cannot be readily used to study hematopoiesis in human beings. Therefore, there is a critical need to develop strategies to assess cellular dynamics within human hematopoietic tissues in vivo. Recently, researchers have used naturally acquired somatic mutations, coupled with other single-cell technologies, to retrospectively analyze clonal cellular dynamics. In summer 2022, the International Society for Experimental Hematology's New Investigator Committee hosted a webinar focused on novel approaches to dissect fetal and adult hematopoiesis, with presentations from Drs. Ana Cvejic and Vijay Sankaran. Here, we provide an overview of these exciting technological advances and some of the novel insights they have already provided in studying human hematopoiesis. [ABSTRACT FROM AUTHOR]

Background: An objective assessment of factors for ocular inflammation and its sequelae and diagnostic assessment of possible development of the sequelae in early phases of uveitis are essential for early and effective treatment of endogenous uveitis. Purpose: To determine whether it is possible to predict optic atrophy in patients with anterior uveitis using computed tomography (CT)-based assessment of optic nerve diameter. Material and Methods: Patients with anterior uveitis underwent a routine eye examination (ophthalmoscopy, biomicroscopy, intraocular pressure (IOP) measurement, and Humphrey perimetry). In addition, they underwent CT-based assessment of optic disc diameter at 3-5 mm from the entrance into the orbit in the affected eye and the contralateral healthy eye. Patients received treatment as per the protocol. Results: The percentage difference in optic nerve diameter between patients with uveitis complicated by optic neuritis and those with uveitis only for affected eyes was large (33.1%) and statistically significant. At 3 months and 6 months after initiation of treatment, mean optic disc diameter in patients with optic neuritis decreased by 37.2% and 49.1%, respectively, compared to baseline values. At 6 months, a decrease in optic nerve diameter among optic neuritis patients was observed both in those who received treatment and in those who failed to receive treatment, but was less marked in the former patients. Particularly, from 3 months to 6 months, optic nerve diameter decreased by 17.3% in treated optic neuritis patients versus 23.5% in those who remained untreated. Conclusion: CT-based data on the change in the optic nerve diameter at the entrance into the orbit in patients with optic neuritis is an objective characteristic of the presence and grade of atrophic process. Early identification of the potential for development of optic atrophy in individuals with optic neuritis will make it possible to treat them early and, consequently, to prevent or stabilize the process. [ABSTRACT FROM AUTHOR]

Leber hereditary optic neuropathy (LHON) is an important example of mitochondrial blindness with the m.11778G > A mutation in the MT-ND4 gene being the most common disease-causing mitochondrial DNA (mtDNA) variant worldwide. The REFLECT phase 3 pivotal study is a randomized, double-masked, placebo-controlled trial investigating the efficacy and safety of bilateral intravitreal injection of lenadogene nolparvovec in patients with a confirmed m.11778G > A mutation, using a recombinant adeno-associated virus vector 2, serotype 2 (rAAV2/2-ND4). The first-affected eye received gene therapy; the fellow (affected/not-yet-affected) eye was randomly injected with gene therapy or placebo. The primary endpoint was the difference in change from baseline of best-corrected visual acuity (BCVA) in second-affected/not-yet-affected eyes treated with lenadogene nolparvovec versus placebo at 1.5 years post-treatment, expressed in logarithm of the minimal angle of resolution (LogMAR). Forty-eight patients were treated bilaterally and 50 unilaterally. At 1.5 years, the change from baseline in BCVA was not statistically different between second-affected/not-yet-affected eyes receiving lenadogene nolparvovec and placebo (primary endpoint). A statistically significant improvement in BCVA was reported from baseline to 1.5 years in lenadogene nolparvovec-treated eyes: -0.23 LogMAR for the first-affected eyes of bilaterally treated patients (p < 0.01); and -0.15 LogMAR for second-affected/not-yet-affected eyes of bilaterally treated patients and the first-affected eyes of unilaterally treated patients (p < 0.05). The mean improvement in BCVA from nadir to 1.5 years was -0.38 (0.052) LogMAR and -0.33 (0.052) LogMAR in first-affected and second-affected/not-yet-affected eyes treated with lenadogene nolparvovec, respectively (bilateral treatment group). A mean improvement of -0.33 (0.051) LogMAR and -0.26 (0.051) LogMAR was observed in first-affected lenadogene nolparvovec-treated eyes and second-affected/not-yet-affected placebo-treated eyes, respectively (unilateral treatment group). The proportion of patients with one or both eyes on-chart at 1.5 years was 85.4% and 72.0% for bilaterally and unilaterally treated patients, respectively. The gene therapy was well tolerated, with no systemic issues. Intraocular inflammation, which was mostly mild and well controlled with topical corticosteroids, occurred in 70.7% of lenadogene nolparvovec-treated eyes versus 10.2% of placebo-treated eyes. Among eyes treated with lenadogene nolparvovec, there was no difference in the incidence of intraocular inflammation between bilaterally and unilaterally treated patients. Overall, the REFLECT trial demonstrated an improvement of BCVA in LHON eyes carrying the m.11778G > A mtDNA mutation treated with lenadogene nolparvovec or placebo to a degree not reported in natural history studies and supports an improved benefit/risk profile for bilateral injections of lenadogene nolparvovec relative to unilateral injections. [ABSTRACT FROM AUTHOR]