bims-ripira Biomed News
on RRM2B MDMD in Adults
Issue of 2025–12–28
nine papers selected by
Martín Lopo



  1. Biochemistry (Mosc). 2025 Dec;90(12): 1849-1861
      The quantitative content of mitochondrial DNA (mtDNA) - a multicopy circular genome - is an important parameter relevant for function of mitochondrial oxidative phosphorylation (OxPhos) in cells, since mtDNA encodes 13 essential OxPhos proteins, 22 tRNAs, and 2 rRNAs. In contrast to the nuclear genome, where almost all lesions have to be repaired, the multicopy nature of mtDNA allows the degradation of severely damaged genomes. Therefore, cellular mtDNA maintenance and its copy number not only depend on replication speed and repair reactions. The speed of intramitochondrial mtDNA degradation performed by a POLGexo/MGME1/TWNK degradation complex and the breakdown rate of entire mitochondria (mitophagy) are also relevant for maintaining the required steady state levels of mtDNA. The present review discusses available information about the processes relevant for turnover of mitochondrial DNA, which dysbalance leads to mtDNA maintenance disorders. This group of mitochondrial diseases is defined by pathological decrease of cellular mtDNA copy number and can be separated in diseases related to decreased mtDNA synthesis rates (due to direct replication defects or mitochondrial nucleotide pool dysbalance) or diseases related to increased breakdown of entire mitochondria (due to elevated mitophagy rates).
    Keywords:  determinants of cellular mtDNA content; mtDNA degradation; mtDNA maintenance; mtDNA maintenance disorders; mtDNA replication
    DOI:  https://doi.org/10.1134/S0006297925602485
  2. Cell Death Discov. 2025 Dec 24.
      Mitochondrial dysfunction is one of the core drivers of aging. It is manifested by reactive oxygen species (ROS) accumulation, mitochondrial DNA (mtDNA) mutations, imbalanced energy metabolism, and abnormal biosynthesis. Mitochondrial autophagy maintains cellular homeostasis by selectively removing damaged mitochondria through mechanisms including the ubiquitin-dependent pathway (PINK1/Parkin pathway) and the ubiquitin-independent pathway (mediated by receptors such as BNIP3/FUNDC1). During aging, the decrease in mitochondrial autophagy efficiency leads to the accumulation of damaged mitochondria, forming a cycle of mitochondrial damage-ROS-aging damage and aggravating aging-related diseases such as neurodegenerative diseases and cardiovascular pathologies. The targeted regulation of mitochondrial autophagy (drug modulation and exercise intervention) can restore mitochondrial function and slow aging. However, autophagy has a double-edged sword effect; moderate activation is anti-aging, but excessive activation or dysfunction accelerates the pathological process. Therefore, targeting mitochondrial autophagy may be an effective anti-aging technique; however, future focus should be on the tissue-specific regulatory threshold and the dynamic balance mechanism to achieve precise intervention.
    DOI:  https://doi.org/10.1038/s41420-025-02913-y
  3. J Transl Med. 2025 Dec 23. 23(1): 1415
      Mitochondria function as the primary energy hubs of cells and possess semi-autonomous genetic characteristic. Mutations in mitochondrial DNA (mtDNA) frequently lead to severe illness and even premature death. The rapid advancement of gene therapy offers promising potential for correcting such disorders. This review first aims to delineate the mechanisms of gene therapy strategies applicable to mitochondrial diseases, including the allotopic expression of mtDNA in the nucleus, mitochondrial-targeted nuclease cleavage, and mtDNA-targeted base editing. It also discusses in detail the clinical efficacy of mtDNA allotopic expression and the preclinical progress of other strategies. Furthermore, the unique physiological features of mitochondria, such as heteroplasmy and independent molecular transport mechanisms, pose distinct challenges for the clinical implementation of mitochondrial gene therapy strategies. Accordingly, this review elaborates on the current limitations of each approach. Finally, it highlights potential optimization directions to address these challenges, emphasizing that understanding heteroplasmy dynamics and their corresponding phenotypes, ensuring the safe delivery and tissue-specific expression of therapeutic elements, and maintaining long-term therapeutic specificity and efficiency are essential for the clinical translation of mitochondrial gene therapy.
    Keywords:  Allotopic expression; Base editing; Mitochondrial DNA; Mitochondrial disorders; Nuclease
    DOI:  https://doi.org/10.1186/s12967-025-07420-3
  4. Alzheimers Dement. 2025 Dec;21 Suppl 2 e104338
       BACKGROUND: Mitochondrial dysfunction is an integral feature of both aging and neurodegenerative diseases, where it significantly contributes to disease progression. It is, therefore, of the utmost importance to understand the underlying mechanisms so that effective therapeutic approaches can be developed. This article delves into specific pathways where mitochondrial dysfunction occurs in aging and neurodegenerative conditions in the hope of discovering potential targets for intervention.
    METHODS: A comprehensive literature review was done to synthesize current knowledge on mitochondrial dysfunction in ageing and neurodegeneration. It focused on the key cellular and molecular pathways that include changes in mitochondrial structure and function, disruptions in energy metabolism, and their impact on cellular homeostasis.
    RESULTS: In short, the overall data point to complex interactions between the processes of aging, neurodegenerative disease and mitochondrial dysfunction. During aging, mitochondria become functionally less effective, characterized by decreased ATP levels, impaired oxidative phosphorylation and increased reactive oxygen species production. Different neurodegenerative diseases- Alzheimer's disease, Parkinson's disease, Huntington's disease-had specific abnormalities in mitochondria, including deficient mitophagy, altered dynamics of mitochondria, and mutation in mitochondrial DNA. These cause neuronal cell death and accelerate progression of the diseases.
    CONCLUSION: This study elucidates the diverse mechanisms that connect mitochondrial dysfunction with both ageing and neurodegenerative diseases. Various pathways identified in this review are considered critical areas for therapeutic intervention aimed at preserving mitochondrial integrity and subsequently reducing detrimental impact of ageing and neurodegeneration on cellular function. These mechanisms offer more complex avenues for research into these critical pathways that should lead to novel treatments for age-related and neurodegenerative conditions.
    DOI:  https://doi.org/10.1002/alz70856_104338
  5. Curr Opin Rheumatol. 2025 Dec 24.
       PURPOSE OF REVIEW: Significant progress has been made in improving the outcomes of patients with systemic lupus erythematosus (SLE) largely through advances in drug discovery as well as enhancements in overall clinical management. This review provides insights into the basis for observed improvements in long-term outcomes through analyses of organ damage, mortality, healthcare utilization, and quality of life.
    RECENT FINDINGS: Patients with SLE in the first half of the twentieth century faced a 50% chance of surviving beyond 7 years. However, in modern times, age standardized mortality has greatly improved, and comorbidities that adversely affect outcomes are receiving far more attention than in prior eras.
    SUMMARY: It is a remarkable era for patients with SLE, with multiple targeted therapies transforming management. Yet, damage prevention still begins with early diagnosis and rapid attainment of remission. Treat to target strategies should be coupled with adjunctive measures, such as strict blood pressure control as well as cardiovascular and metabolic risk management.
    Keywords:  lupus nephritis; lupus outcomes; mortality trends; remission in systemic lupus erythematosus; systemic lupus erythematosus; systemic lupus erythematosus damage
    DOI:  https://doi.org/10.1097/BOR.0000000000001144
  6. Alzheimers Dement. 2025 Dec;21 Suppl 1 e102364
       BACKGROUND: In the nervous system, mitochondria can be transferred between neural cells through intercellular tunneling nanotubes (TNTs), microvesicles, or as free organelles. This transfer not only alters the mitochondrial content and respiration of recipient neural cells but also triggers a profound rewiring of their physiology, with glial cells and immune responses playing key roles in this reconfiguration.
    METHOD: Primary co-cultures of neurons and glial cells, along with in vivo analysis of mitochondrial transfer in mouse brains, were monitored using kinetic microscopy, flow cytometry, and metabolic flux analyses to explore the physiological changes in neural cells. Mitochondrial DNA (mtDNA) transmission was tracked through RT-PCR and ARMS-PCR to examine hierarchical transfer and acquisition.
    RESULT: Communication between neural cells, particularly through TNTs, shows dynamic mitochondrial transfer, regulated by mitochondrial transport, fusion, and fission events. These events respond to structural and signaling changes in intercellular communication, mainly via TNTs. As a result, transmitted mitochondria reconfigure the content, metabolism, and mtDNA composition in recipient neurons and astrocytes. Notably, we observe a significant role of microglia and astrocytes upon mitochondrial acquisition in mouse brains, suggesting inflammatory events that may coordinate mitochondrial transfer as key regulators of metabolic rewiring and cognitive effects in the nervous system.
    CONCLUSION: Our findings provide evidence that a multilayered mitochondrial transfer is a critical mechanism for reconfiguring neural metabolism, immune responses, and overall neural physiology.
    DOI:  https://doi.org/10.1002/alz70855_102364
  7. Mol Ther. 2025 Dec 24. pii: S1525-0016(25)01064-0. [Epub ahead of print]
      Mitochondrial myopathies are often caused by heteroplasmic mutations in the mitochondrial DNA (mtDNA). In muscle, biochemical, pathological, and clinical impairments are observed only when the ratios of mutant/wild-type mtDNA are high. Because reductions in mutant mtDNA loads are essentially permanent, we reasoned that transient expression of a therapeutic mitochondrial nuclease could be sufficient to permanently alter heteroplasmy. We expressed a mitochondrial targeted gene editing nuclease (mitoARCUS) via intramuscular injection of lipid nanoparticle (LNP)/mRNA complexes in a mouse model of mtDNA disease (m.5024C>T in the mt-tRNAAla gene). Transient expression of mitoARCUS in the tibialis anterior (TA) led to a robust decrease in mtDNA mutation load which was maintained up to forty-two weeks after injection. A molecular marker of the mitochondrial defect in this model, namely low levels of mt-tRNAAla, were markedly improved in treated muscles. Muscle force assessment in situ after repeated stimulation showed that fatigability was improved in the treated TA. Finally, we showed that multi-muscle injections can alter mtDNA heteroplasmy essentially in whole limbs. These results demonstrate that transient expression of mitoARCUS via LNP/mRNA intramuscular injections have long-lasting positive effects in muscles afflicted with mitochondrial myopathy.
    DOI:  https://doi.org/10.1016/j.ymthe.2025.12.041
  8. bioRxiv. 2025 Dec 15. pii: 2025.12.12.693865. [Epub ahead of print]
      The contribution of mitochondrial genetics to heart failure is thought to be reciprocal. Its complex traits are influenced by genetic and environmental factors. Genetically diverse mouse strains form a vital repository to uncover the interaction between the mitochondrial and nuclear genomes underlying heart failure due to their traceable genetic origins, maternal lineages and controlled genetic variation. Using systems genetics, we studied this cross-talk in the Collaborative Cross (CC) mice challenged with heart failure (HF). We used 63 strains of CC-mice that grouped into 8 mitochondrial haplotypes and subjected them to HF using isoproterenol (Iso), a beta-adrenergic stimulant that mimics progressive stress induced HF in humans. The Alzet osmotic pumps delivered a consistent dose of the drug for 21 days following which the mice were euthanized for organ collection. A group of mice with saline loaded pumps acted as control (Ctrl). Baseline and end of study echocardiography were recorded for these mice. Bulk RNA sequencing was carried out on the left ventricles and data analyzed on R-studio. The CC-strains showed differences across the haplotypes for organ weights and heart function. Noticeable treatment specific gene expression differences were observed for 34 nuclear encoded genes from MitoCarta3.0 unlike mt-DNA encoded genes that were insignificant after correcting for sex and haplotypes. These genes were associated with multiple metabolic pathways in the cell. Trait-GWAS associations with markers from the mitochondrial genome were observed only for mice from Iso group with cell surface area (p = 6.19e-06) and change in ejection fraction (p = 9.22e-05) as top hits under FWER threshold of 0.01. Cyfip2 was the top candidate gene (p = 2.66e-07) among the 831 hits (47-MitoCarta & 784 other nuclear) based on our trans-eQTL analysis. The eQTL genes influenced critical pathways of OXPHOS, myogenesis, apoptosis etc. Our approach uncovered 24 gene candidates associated with mt-DNA and HF that overlapped with our previous mi-eQTL reports. CC-mice revealed ancestry dependent effects underlying HF for studying mito-nuclear interactions. Despite establishing differences, modeling these interaction needs development of complex cybrid systems to evaluate the bidirectional impact on HF.
    Author Summary: The Collaborative Cross (CC) mouse is a genetically diverse population that has been used to study complex diseases. Recently, our group has comprehensively characterized the heart from 63 strains of the CC and reported genetic associations with heart failure (HF). Traditionally, genetic abnormalities underlying a disease are related to the nuclear genome but there exists an alternate genome within the cells, the mitochondrial DNA (mt-DNA), whose contribution is understudied. The mt-DNA of CC mice is maternally derived from the 8 founder strains, and our sequencing data holds this information, allowing us the ability to use them to study the contribution of mitochondrial ancestry (haplotypes) to HF. We found haplotype differences in terms of cardiac function and gene expression (both nuclear and mitochondrial) that were associated with HF. It revealed stress induced changes in the heart (trait and gene expression) linked with regions in the mt-DNA that encode genes involved in oxidative phosphorylation and metabolism. We uncovered 24 high-confidence nuclear gene candidates that agreed with our previous analyses and were associated with regions on the mt-DNA. These findings open up new opportunities to study the CC and advance the understanding of Mito-nuclear interactions in HF pathophysiology.
    DOI:  https://doi.org/10.64898/2025.12.12.693865
  9. bioRxiv. 2025 Dec 11. pii: 2025.12.08.693036. [Epub ahead of print]
       Background: Adults and children with cerebral cavernous malformations (CCMs) are at risk of experiencing lifelong complications such as hemorrhagic strokes, neurological deficits, and epileptic seizures. These complications can severely reduce quality of life. At present, there is no safe or effective therapeutic option for the long-term treatment of CCMs.
    Methods: Using advanced artificial intelligence (AI) and machine learning models, powered by the Benevolent Platform™, we aimed to identify therapeutic drug targets for CCM pathology (e.g., CCM1, CCM2, CCM3). An AI integrative approach utilized various data types from biomedical entities, including diseases, genes, tissues, and biological mechanisms, together with CCM transcriptomic experimental data. High-throughput drug screening of AI-selected FDA-approved medications, analyses of mitochondrial morphology, and studies on pharmacokinetics, pharmacodynamics, and toxicology were conducted in CCM animal models to identify drugs that could potentially be repurposed for the long-term treatment of CCM disease.
    Results: AI predicted the AMPK (AMP-activated protein kinase) and mTOR (mammalian target of rapamycin) pathways as potential therapeutic targets that contribute to CCM pathology. High-content screening validation revealed that the FDA-approved drug metformin, which acts as an AMPK agonist and mTOR inhibitor, can reverse changes in cell-cell junction organization and increase KLF4 expression, a marker for CCM, in human CCM endothelial cells in cultured assays. In addition, pharmacodynamic markers of metformin were observed in CCM mouse models ( Slco1c1-iCreERT2;Krit1 fl/fl ;Pten fl/wt and Slco1c1-iCreERT2;Pdcd10 fl/fl ) including reduced S6 kinase or ribosomal protein phosphorylation, a marker of decrease mTOR signaling, and increased AMPK phosphorylation, a marker of AMPK activation, that corresponded to reduced lesion burden. Pharmacokinetic and toxicological studies in CCM animal models showed that that metformin penetrates the brain and long-term administration has a favorable safety profile. We also demonstrated that brain endothelial cells in chronic CCM mouse models exhibit increased levels of the inflammatory marker VCAM-1, which is associated with altered mitochondrial phenotypes, as observed by immunofluorescence, MITO-tagging, and electron microscopy analysis. Additionally, we discovered that metformin and a potent AMPK activator, PF-06409577, can reverse mitochondrial phenotypic changes in brain endothelial cells and reduce the elevation of VCAM-1 expression associated with chronic CCM disease. Therefore, metformin can provide cytoprotection and may reverse the CCM endothelial phenotype by activating AMPK.
    Conclusions: Predictions using AI technology and high-throughput drug screening, combined with pharmacokinetic, pharmacodynamic, and toxicological studies in CCM animal models, identified metformin as a promising drug candidate for repurposing for the long-term treatment of CCM disease. We propose that metformin enhances metabolic adaptation to brain vascular malformations by activating AMPK, which helps reverse mitochondrial fragmentation in brain endothelial cells.
    Graphical abstract:
    DOI:  https://doi.org/10.64898/2025.12.08.693036