bims-curels Biomed News
on Leigh syndrome
Issue of 2024‒03‒31
twelve papers selected by
Cure Mito Foundation

  1. Front Biosci (Schol Ed). 2024 Mar 14. 16(1): 7
      Disorders of mitochondrial function are responsible for many inherited neuromuscular and metabolic diseases. Their combination of high mortality, multi-systemic involvement, and economic burden cause devastating effects on patients and their families. Molecular diagnostic tools are becoming increasingly important in providing earlier diagnoses and guiding more precise therapeutic treatments for patients suffering from mitochondrial disorders. This review addresses fundamental molecular concepts relating to the pathogenesis of mitochondrial dysfunction and disorders. A series of short cases highlights the various clinical presentations, inheritance patterns, and pathogenic mutations in nuclear and mitochondrial genes that cause mitochondrial diseases. Graphical and tabular representations of the results are presented to guide the understanding of the important concepts related to mitochondrial molecular genetics and pathology. Emerging technology is incorporating preimplantation genetic testing for mtDNA disorders, while mitochondrial replacement shows promise in significantly decreasing the transfer of diseased mitochondrial DNA (mtDNA) to embryos. Medical professionals must maintain an in-depth understanding of the gene mutations and molecular mechanisms underlying mitochondrial disorders. Continued diagnostic advances and comprehensive management of patients with mitochondrial disorders are essential to achieve robust clinical impacts from comprehensive genomic testing. This is especially true when supported by non-genetic tests such as biochemical analysis, histochemical stains, and imaging studies. Such a multi-pronged investigation should improve the management of mitochondrial disorders by providing accurate and timely diagnoses to reduce disease burden and improve the lives of patients and their families.
    Keywords:  maternal inheritance; mitochondrial disorders; mitochondrial genome
  2. J Neurol. 2024 Mar 28.
      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.
    Keywords:  CMT; Genetic heterogeneity; Genome-phenome analysis platform (GPAP); Mitochondrial disease; Peripheral neuropathies; Rare variants
  3. Camb Prism Precis Med. 2023 ;1 e6
      Mitochondria play a key role in cell homeostasis as a major source of intracellular energy (adenosine triphosphate), and as metabolic hubs regulating many canonical cell processes. Mitochondrial dysfunction has been widely documented in many common diseases, and genetic studies point towards a causal role in the pathogenesis of specific late-onset disorder. Together this makes targeting mitochondrial genes an attractive strategy for precision medicine. However, the genetics of mitochondrial biogenesis is complex, with over 1,100 candidate genes found in two different genomes: the nuclear DNA and mitochondrial DNA (mtDNA). Here, we review the current evidence associating mitochondrial genetic variants with distinct clinical phenotypes, with some having clear therapeutic implications. The strongest evidence has emerged through the investigation of rare inherited mitochondrial disorders, but genome-wide association studies also implicate mtDNA variants in the risk of developing common diseases, opening to door for the incorporation of mitochondrial genetic variant analysis in population disease risk stratification.
    Keywords:  genetic polymorphism; genetic risk score; genetics; genomics; metabolic diseases
  4. Stem Cell Res. 2024 Mar 24. pii: S1873-5061(24)00104-1. [Epub ahead of print]77 103406
      Leber hereditary optic neuropathy (LHON) is one of the most common mitochondrial illness, causing retinal ganglion cell degeneration and central vision loss. It stems from point mutations in mitochondrial DNA (mtDNA), with key mutations being m.3460G > A, m.11778G > A, and m.14484 T > C. Fibroblasts from identical twins, sharing m.14484 T > C and m.10680G > A variants each with 70 % heteroplasmy, were used to generate iPSC lines. Remarkably, one twin, a LHON patient, displayed symptoms, while the other, a carrier, remained asymptomatic. These iPSCs offer a valuable tool for studying factors influencing disease penetrance and unravelling the role of m.10680G > A, which is still debated.
  5. Front Neurol. 2024 ;15 1305404
      Background: Lennox-Gastaut syndrome (LGS), a severe developmental epileptic encephalopathy, has various underlying causes. Mitochondrial respiratory chain complex I (MRC I) deficiency is an important cause of metabolic disorders such as mitochondrial dysfunction that can compromise brain function, thereby causing intractable epilepsy, including LGS. Thus, it can be expected that the presence or absence of MRC I deficiency may affect the treatment outcome of patients with LGS.Objectives: In this retrospective study, we aimed to investigate differences in the epilepsy characteristics and treatment outcomes between patients with LGS with and without MRC I deficiency.
    Methods: We retrospectively reviewed the medical records of 92 patients with LGS. We divided 68 patients with LGS according to the presence (n = 30) or absence (n = 38) of MRC I deficiency and compared their epilepsy characteristics.
    Results: Generalized tonic and drop seizures were significantly worse in patients with LGS and MRC I deficiency than in those without MRC I deficiency group at the 1-year follow-up (p < 0.001) and final follow-up 1 (p < 0.001). Patients with LGS and MRC I deficiency had significantly fewer electroencephalogram (EEG) improvements compared to those without MRC I deficiency at the 1-year follow-up (p = 0.031). Additionally, in the final follow-up period, patients with LGS and MRC I deficiency had significantly less improvement in EEG findings compared to patients without MRC I deficiency (p < 0.001).
    Conclusion: The overall treatment prognosis-in terms of improvement in traumatic generalized tonic seizure, drop seizure, and EEG findings-is worse in patients with LGS and MRC I deficiency than that in patients with LGS but without MRC I deficiency. Additional and targeted treatment is required to treat LGS with MRC I deficiency.
    Keywords:  Lennox–Gastaut syndrome (LGS); epilepsy; mitochondrial disease; mitochondrial dysfunction; mitochondrial respiratory chain complex I deficiency
  6. Biochim Biophys Acta Mol Basis Dis. 2024 Mar 21. pii: S0925-4439(24)00120-0. [Epub ahead of print] 167131
      Mitochondrial DNA (mtDNA) deletions which clonally expand in skeletal muscle of patients with mtDNA maintenance disorders, impair mitochondrial oxidative phosphorylation dysfunction. Previously we have shown that these mtDNA deletions arise and accumulate in perinuclear mitochondria causing localised mitochondrial dysfunction before spreading through the muscle fibre. We believe that mito-nuclear signalling is a key contributor in the accumulation and spread of mtDNA deletions, and that knowledge of how muscle fibres respond to mitochondrial dysfunction is key to our understanding of disease mechanisms. To understand the contribution of mito-nuclear signalling to the spread of mitochondrial dysfunction, we use imaging mass cytometry. We characterise the levels of mitochondrial Oxidative Phosphorylation proteins alongside a mitochondrial mass marker, in a cohort of patients with mtDNA maintenance disorders. Our expanded panel included protein markers of key signalling pathways, allowing us to investigate cellular responses to different combinations of oxidative phosphorylation dysfunction and ragged red fibres. We find combined Complex I and IV deficiency to be most common. Interestingly, in fibres deficient for one or more complexes, the remaining complexes are often upregulated beyond the increase of mitochondrial mass typically observed in ragged red fibres. We further find that oxidative phosphorylation deficient fibres exhibit an increase in the abundance of proteins involved in proteostasis, e.g. HSP60 and LONP1, and regulation of mitochondrial metabolism (including oxidative phosphorylation and proteolysis, e.g. PHB1). Our analysis suggests that the cellular response to mitochondrial dysfunction changes depending on the combination of deficient oxidative phosphorylation complexes in each fibre.
    Keywords:  Cell signalling; Mitochondrial DNA deletion; Mitochondrial disease; Myopathy; OXPHOS
  7. Int J Mol Sci. 2024 Mar 14. pii: 3303. [Epub ahead of print]25(6):
      Mitochondria are eukaryotic cellular organelles that function in energy metabolism, ROS production, and programmed cell death. Cutaneous epithelial and hair follicle dermal papilla cells are energy-rich cells that thereby may be affected by mitochondrial dysfunction and DNA mutation accumulation. In this review, we aimed to summarize the medical literature assessing dermatologic conditions and outcomes associated with mitochondrial dysfunction. A search of PubMed and Embase was performed with subsequent handsearching to retrieve additional relevant articles. Mitochondrial DNA (mtDNA) deletions, mutation accumulation, and damage are associated with phenotypic signs of cutaneous aging, hair loss, and impaired wound healing. In addition, several dermatologic conditions are associated with aberrant mitochondrial activity, such as systemic lupus erythematosus, psoriasis, vitiligo, and atopic dermatitis. Mouse model studies have better established causality between mitochondrial damage and dermatologic outcomes, with some depicting reversibility upon restoration of mitochondrial function. Mitochondrial function mediates a variety of dermatologic conditions, and mitochondrial components may be a promising target for therapeutic strategies.
    Keywords:  UVR; aging; atopic dermatitis; dermatology; hair loss; lupus; mitochondria; psoriasis; vitiligo; wound healing
  8. Front Biosci (Schol Ed). 2024 Mar 13. 16(1): 6
      BACKGROUND: Metabolic disorders, including obesity, are often accompanied by an increased risk of cardiovascular complications. Monocytes are the common link between obesity and cardiovascular diseases (CVDs). The bias of innate cellular immunity towards pro-inflammatory activation stimulates the development of diseases associated with chronic inflammation, in particular metabolic disorders, including obesity, as well as CVDs. Disorders in the functional state of monocytes and activation of inflammation may be associated with mitochondrial dysfunction. Mutations accumulating in mitochondrial DNA with age may lead to mitochondrial dysfunction and may be considered a potential marker for developing chronic inflammatory diseases.METHODS: The present study aimed to study the relationship between mitochondrial heteroplasmy in CD14+ monocytes and cardiovascular risk factors in 22 patients with obesity and coronary heart disease (CHD) by comparing them to 22 healthy subjects.
    RESULTS: It was found that single-nucleotide variations (SNV) A11467G have a negative correlation with total cholesterol (r = -0.82, p < 0.05), low density lipoproteins (LDL) (r = -0.82, p < 0.05), with age (r = -0.57, p < 0.05) and with mean carotid intima-media thickness (cIMT) (r = -0.43, p < 0.05) and a positive correlation with HDL level (r = 0.71, p < 0.05). SNV 576insC positively correlated with body mass index (BMI) (r = 0.60, p < 0.001) and LDL level (r = 0.43, p < 0.05). SNV A1811G positively correlated with mean cIMT (r = 0.60, p < 0.05).
    CONCLUSIONS: It was revealed that some variants of mitochondrial DNA (mtDNA) heteroplasmy are associated with CVD risk factors. The results demonstrate the potential for using these molecular genetic markers to develop personalized CVD and metabolic disorder treatments.
    Keywords:  cardiovascular diseases; inflammation; mitochondria; monocytes; mtDNA mutations
  9. Healthc Manage Forum. 2024 Mar 29. 8404704241239862
      Patient engagement is emerging as a priority for Canadian health leaders. Alongside the proliferation of patient engagement efforts in healthcare organizations and networks, awareness that tokenism can potentially occur within such efforts, as well as strategies to mitigate it, are gaining increased attention. While many actions associated with more tokenistic forms of patient engagement have been identified, this article posits there is a need to pay critical attention to the concept and role of power in enabling these actions in the first place. Of particular importance is how power and knowledge work to shape healthcare organizations and can create unequal relations with the patients they seek to engage. Drawing on the literature, this article serves as a theoretical roadmap for health leaders to think critically about power, as well as a set of prompts that can be used to reflexively consider their role in navigating power dynamics in the context of patient engagement efforts. This article contends that building awareness of power is a critical step for health leaders and organizations and that navigating power differences is a necessary leadership competency for engaging patients in decision-making throughout all stages of healthcare improvement and organizational change efforts.
  10. J Cent Nerv Syst Dis. 2024 ;16 11795735241241423
      MNGIE (Mitochondrial Neurogastrointestinal Encephalomyopathy) is an ultra-rare autosomal recessive disorder that leads to mutations in the nuclear genes encoding thymidine phosphorylase. Symptoms include gastrointestinal dysmotility, cachexia, ptosis, external ophthalmoplegia, sensorimotor neuropathy and asymptomatic leukoencephalopathy. We describe the first case of MNGIE with meningoencephalitis that ultimately led to a familial diagnosis ending a diagnostic odyssey. We retrospectively reviewed the electronic medical records and sent whole exome sequencing for the index case and his family members. We report the variant c.877T>C p.(Cys293Arg) found in TYMP gene in all affected siblings showed typical clinical manifestations related to MNGIE. To the best of our knowledge, this is not described in the literature nor in the population databases dbSNP (Single Nucleotide Polymorphism Database) and gnomAD (Genome Aggregation Database). Additionally, it is located in a highly conserved residue and the bioinformatic analysis suggests it is most probably deleterious. Moreover, we estimated 550 number of cases of MNGIE (including 5 cases in this study) after performing an extensive search in the literature across 3 databases from 1983-2023. In addition, we identified 44 patients with MNGIE-like phenotype in genes other than TYMP. MNGIE-like phenotype affects POLG1, RRM2B, LIG3, RRM1, MTTV1, and MT-RNR1 genes.
    Keywords:  Mitochondrial neurogastrointestinal encephalomyopathy; atypical; case series; meningoencephalitis; novel mutation
  11. Environ Mol Mutagen. 2024 Mar 24.
      Cervical cancer is the fourth most commonly diagnosed cancer in women and is considered a preventable disease, as vaccination and screening programs effectively reduce its incidence and mortality rates. Disease physiopathology and malignant cell transformation is a complex process, but it is widely known that high-risk HPV (hrHPV) infection is a necessary risk factor for cancer development. Mitochondria, cell organelles with important bioenergetic and biosynthetic functions, are important for cell energy production, cell growth, and apoptosis. Mitochondrial DNA is a structure that is particularly susceptible to quantitative (mtDNA copy number variation) and qualitative (sequence variations) alterations that are associated with various types of cancer. Novel biomarkers with diagnostic and prognostic value in cervical cancer can be evaluated to provide higher specificity and complement hrHPV molecular testing, which is the most recommended method for primary screening. In accordance with this, this review aimed to assess mitochondrial alterations associated with cervical cancer in clinical cervicovaginal samples, in order to unravel their possible role as specific diagnostic and prognostic biomarkers for cervical malignancy, and also to guide the understanding of their involvement in carcinogenesis, HPV infection, and disease progression.
    Keywords:  HPV; cervical cancer; mitochondrial DNA; mitochondrial DNA copy number; mitochondrial DNA mutation
  12. FEBS J. 2024 Mar 28.
      Intercellular communication is pivotal in mediating the transfer of mitochondria from donor to recipient cells. This process orchestrates various biological functions, including tissue repair, cell proliferation, differentiation and cancer invasion. Typically, dysfunctional and depolarized mitochondria are eliminated through intracellular or extracellular pathways. Nevertheless, increasing evidence suggests that intercellular transfer of damaged mitochondria is associated with the pathogenesis of diverse diseases. This review investigates the prevalent triggers of mitochondrial damage and the underlying mechanisms of mitochondrial transfer, and elucidates the role of directional mitochondrial transfer in both physiological and pathological contexts. Additionally, we propose potential previously unknown mechanisms mediating mitochondrial transfer and explore their prospective roles in disease prevention and therapy.
    Keywords:  cell communication; disease; extracellular vesicles; mitochondria; mitochondrial quality control; mitochondrial transfer