bims-ripira 2026-04-26 papers

bims-ripira

Biomed News

on RRM2B MDMD in Adults

Issue of 2026–04–26
thirteen papers selected by
Martín Lopo

Exogenous pyruvate restores mitochondrial bioenergetics by synergizing with the AMPK-mTOR-SIRT3 pathway to alleviate sepsis-associated acute kidney injury.
Protective effects of irisin in sarcopenia: a promising treatment.
Muscular Dystrophy Muscle Preservation: A Comparative Systematic Review of Exercise and Cannabidiol (CBD) Interventions.
Altered mitochondrial ultrastructure in salivary epithelial cells of patients with Sjögren's disease is associated with mitochondrial DNA release and increased activation of pattern recognition receptors: potential use of tofacitinib as therapy.
Vitamin B12 improves skeletal muscle mitochondrial biology in aged mice.
Cholesterol overload promotes mitochondria-mediated apoptosis with impaired mitochondrial unfolded protein response and mitophagy in SH-SY5Y cells.
Spermidine alleviates sepsis-induced cardiomyopathy by improving mitochondrial quality and quantity via a Metallothionein 1-dependent antioxidant pathway.
Early Life Adversity and Mitochondrial Function: Comparing Cumulative Risk and Dimensional Models of Adversity.
The Role of Metal Ions in Mitochondria: From Energy Metabolism to Cell Destiny.
Role of oxidative stress in sepsis: Mechanisms, pathways, and therapeutic strategies.
Benefits and adverse effects of ketogenic diet treatment in pediatric patients with inborn errors of metabolism.
RNA Sequencing Resolves Cryptic Pathogenic Variants in Mitochondrial Disease.
Aminoacyl-tRNA Synthetases: Variant Classification, Functional Assays, and Emerging Therapeutic Strategies.

Chem Biol Interact. 2026 Apr 22. pii: S0009-2797(26)00197-3. [Epub ahead of print] 112089

Exogenous pyruvate restores mitochondrial bioenergetics by synergizing with the AMPK-mTOR-SIRT3 pathway to alleviate sepsis-associated acute kidney injury.

Yueguo Wang, Wenwen Wang, Jian Sun, Shusheng Zhou, Lijun Ni, Mengzhen Dong, Xin Wang, Yuan Yuan, Jie Wang, Pengfei Ren, Wenxiang Fang, Kui Jin.

  Sepsis-associated acute kidney injury (SA-AKI) is closely linked to profound metabolic reprogramming and mitochondrial dysfunction, yet effective metabolic targeted therapies remain limited. In this study, we elucidated the molecular mechanism by which ethyl pyruvate (EP), an exogenous metabolic substrate, alleviates SA-AKI by regulating mitochondrial bioenergetics through the AMPK-mTOR-SIRT3 signaling pathway. Using a cecal ligation and puncture-induced SA-AKI mouse model and LPS-stimulated HK-2 cells, we demonstrated that EP synergized with the AMPK activator AICAR to significantly improve renal function, reduce injury markers and inflammation, and enhance survival. Single-cell RNA sequencing (scRNA-seq) identified extensive metabolic reprogramming in renal epithelial cells during sepsis, characterized by mitochondrial dysfunction and suppression of oxidative phosphorylation (OXPHOS). Mechanistically, combined EP and AICAR treatment, rather than EP alone, alleviated mitochondrial dysfunction by restoring NAD+/NADH balance, increasing mitochondrial DNA (mtDNA) content, improving mitochondrial respiratory chain complex activity, and rebalancing mitochondrial fission-fusion dynamics. Combined EP and AICAR treatment also enhanced autophagy and reduced apoptosis, partly through a SIRT3-dependent mechanism downstream of AMPK-mTOR signaling. This effect was enhanced or diminished by pretreatment with rapamycin (Rapa) or interferon-γ (IFN-γ). Pharmacological inhibition of SIRT3 partially abolished the mitochondrial and cytoprotective benefits of EP, confirming SIRT3 as a key downstream effector of AMPK-mTOR signaling. Collectively, our data identified EP as a metabolic modulator that synergizes with AMPK activation to alleviate SA-AKI. This effect is achieved by restoring mitochondrial function and OXPHOS through the AMPK-mTOR-SIRT3 signaling pathway, providing a mechanistic basis for metabolism-oriented therapeutic strategies in SA-AKI.

Keywords:  AMPK; Ethyl pyruvate (EP); Metabolic reprogramming; Mitochondrial bioenergetics; SIRT3; Sepsis-associated acute kidney injury (SA-AKI)

DOI:  https://doi.org/10.1016/j.cbi.2026.112089
J Orthop Translat. 2026 May;58 101090

Protective effects of irisin in sarcopenia: a promising treatment.

Yixiao Chen, Guoqing Li, Feng Gao, Ruijiang Li, Minghui Yang, Yufeng Ge, Xinbao Wu.

  Sarcopenia is an age-related progressive muscle degeneration condition characterized by loss of muscle mass, muscle strength, and poor physical function. Its prevalence and mortality rates continue to rise with advancing age, significantly impairing patients' quality of life. The pathogenesis of sarcopenia involves multiple pathophysiological processes, including imbalanced protein catabolism, cell death, mitochondrial dysfunction, and various cellular signaling pathways. Therefore, it is crucial to identify potential therapeutic targets and treatments for sarcopenia. As an exercise-induced myokine, irisin has shown great potential in maintaining skeletal muscle health. In this review, we focus on the relationship between irisin and sarcopenia, delving into existing research to elucidate irisin's mechanisms of action in sarcopenia-including its effects on protein catabolism, cell death, mitochondrial dysfunction, cellular signaling, and muscle cell proliferation and differentiation. We provide insights into irisin as a therapeutic intervention for sarcopenia and provide essential evidence to support its clinical application in sarcopenia treatment. The Translational Potential of this Article . This review highlights the mechanism of action of irisin in sarcopenia and its potential as a therapeutic candidate for sarcopenia in the future.

Keywords:  Cell death; Irisin; Protein metabolic balance; Sarcopenia; Signaling pathway; Treatment

DOI:  https://doi.org/10.1016/j.jot.2026.101090
J Biotechnol Biomed. 2026 ;9(1): 77-83

Muscular Dystrophy Muscle Preservation: A Comparative Systematic Review of Exercise and Cannabidiol (CBD) Interventions.

Andre Aabedi, Daniel Masiach, Devendra K Agrawal.

Muscular dystrophy comprises a heterogeneous group of inherited neuromuscular disorders characterized by progressive muscle degeneration, weakness, and functional decline. In the absence of curative pharmacologic therapies, non-pharmacologic strategies aimed at preserving muscle mass and function are of growing clinical importance. Exercise therapy is an established cornerstone of conservative management, whereas cannabidiol supplementation has emerged as a novel experimental intervention supported primarily by preclinical evidence. This systematic review synthesizes and compares the available evidence on exercise therapy and cannabidiol supplementation with respect to muscle mass preservation in muscular dystrophy. Exercise interventions, including aerobic, resistance, and functional training, demonstrate modest but consistent benefits in functional performance, endurance, and quality of life, with acceptable safety profiles when appropriately individualized. In contrast, cannabidiol supplementation has shown promising anti-inflammatory, anti-fibrotic, and myoprotective effects in dystrophic animal models, yet lacks robust human clinical data. Comparative analysis suggests overlapping anti-inflammatory and antioxidant mechanisms, raising the possibility of synergistic benefit; however, combined intervention strategies remain untested. Overall, exercise therapy remains the most evidence-supported approach for muscle preservation in muscular dystrophy, while cannabidiol supplementation warrants cautious investigation through rigorously designed clinical trials. Future research should prioritize head-to-head randomized controlled trials, standardized outcome measures, and subtype-specific therapeutic strategies to clarify the independent and complementary roles of these interventions.

Keywords: Anti-oxidation; Cannabidiol; Exercise therapy; Fibrosis; Inflammation; Muscle mass preservation; Muscular dystrophy; Neuromuscular disease; Non-pharmacologic interventions
Ann Rheum Dis. 2026 Apr 17. pii: S0003-4967(26)00208-6. [Epub ahead of print]

Altered mitochondrial ultrastructure in salivary epithelial cells of patients with Sjögren's disease is associated with mitochondrial DNA release and increased activation of pattern recognition receptors: potential use of tofacitinib as therapy.

Patricia Carvajal, Isabel Castro, Félix Urra, Sergio Aguilera, Sergio González, Claudio Molina, Salvador Campos, Gonzalo Ramírez, Cristopher Chávez, Juan Gutiérrez, María José Yáñez, María-Julieta González, María-José Barrera.

OBJECTIVES: This study aimed to analyse structural and functional mitochondrial alterations, the release of mitochondrial DNA (mtDNA), and the activation of inflammatory signalling pathways that can be reversed by tofacitinib in the salivary glands (SG) of patients with Sjögren's disease (SjD).
METHODS: SG from patients with SjD and controls, as well as from mice with SjD treated with or without tofacitinib, were analysed. We determined the mitochondrial ultrastructure, the presence of mtDNA in the cytosol, and the levels and localisation of pattern recognition receptors (PRRs) that recognise mtDNA. The adenosine triphosphate (ATP) levels and oxygen consumption rate (OCR) were measured to evaluate mitochondrial respiration in frozen SG. We also evaluated the OCR in human submandibular gland cells incubated with interferon-gamma (IFN-γ), tofacitinib, or both.
RESULTS: Increased mtDNA release into the cytosol was observed in SG epithelial cells of patients with SjD. This change was linked with increased PRR activation (cyclic GMP-AMP synthase, Z-DNA-binding protein 1, and nucleotide-binding oligomerisation domain-like receptor protein 3) and decreased mitochondrial transcription factor A (TFAM). Similar mitochondrial ultrastructural alterations and increased PRR activation were observed in the SG of the SjD mouse model. These changes were reversed by tofacitinib. Interestingly, increased activity of electron transport chain complexes was observed in SG of patients with SjD, which could be modulated by IFN-γ, as observed in vitro. We also found that tofacitinib stabilised mitochondrial function at basal conditions in vitro, counteracting the mitochondrial adaptations induced by IFN-γ.
CONCLUSIONS: Taken together, these results suggest that mitochondrial alterations are linked with inflammation and support the potential use of tofacitinib in patients with SjD.

DOI: https://doi.org/10.1016/j.ard.2026.03.022
Geroscience. 2026 Apr 24.

Vitamin B12 improves skeletal muscle mitochondrial biology in aged mice.

Abigail R Williamson, Angad Yadav, Wenxia Ma, Susan Schmitt, Shelby Rorrer, Lauren E Odom, Luisa F Castillo, Chloe T Purello, Olga V Malysheva, James Mobley, Martha Field, Anna E Thalacker-Mercer.

  Age-related skeletal muscle deterioration is a commonly reported disability among older adults, attributed to several factors including mitochondrial dysfunction, a major hallmark of aging. Therapies to attenuate or reverse mitochondrial decline are limited. Despite identified positive relationships between vitamin B12 (B12) and mitochondrial biology, the impact of B12 supplementation on skeletal muscle mitochondria, in advanced age, has not been examined. Thus, the impact of B12 supplementation on skeletal muscle mitochondrial biology was examined in aged female mice, given 12 weeks of B12 supplementation (SUPP) or vehicle control. In the mouse model, mitochondrial DNA and content were measured with PCR and citrate synthase activity, respectively; mitochondrial morphology was examined using transmission electron microscopy; mitochondrial function was examined using extracellular metabolic flux analysis; and proteins and pathway enrichment was identified with proteomics. The results demonstrated that SUPP in aged mice increased muscle mitochondrial content and improved morphology. Further, differentially expressed proteins were enriched in TCA cycle, OXPHOS, and oxidative stress pathways. This is the first study, to our knowledge, examining the impact of B12 supplementation on skeletal muscle mitochondrial biology in aged female mice. Results suggest that B12 supplementation improves mitochondrial biology in aged female mice.

Keywords:  Aging; Mitochondria; Sarcopenia; Skeletal muscle; Vitamin B12

DOI:  https://doi.org/10.1007/s11357-026-02264-1
Food Chem Toxicol. 2026 Apr 20. pii: S0278-6915(26)00180-8. [Epub ahead of print] 116106

Cholesterol overload promotes mitochondria-mediated apoptosis with impaired mitochondrial unfolded protein response and mitophagy in SH-SY5Y cells.

Juhyun Chung, Je Won Ko, Young Hye Kwon.

  Cholesterol accumulation in the brain has been implicated in mitochondrial dysfunction and neurodegeneration; however, its specific effects on mitochondrial quality control pathways, including the mitochondrial unfolded protein response (UPRmt) and mitophagy, remain poorly defined. In this study, SH-SY5Y human neuroblastoma cells were treated with 25 or 50 μg/mL water-soluble cholesterol for 24 h. UPRmt, mitophagy, and inflammasome activation were assessed using molecular and cellular approaches, including immunoblotting, quantitative RT-PCR, and fluorescence-based imaging. Cholesterol treatment increased intracellular cholesterol levels up to 1.7-fold and induced dose-dependent cytotoxicity and apoptosis. UPRmt was suppressed, as evidenced by reduced expression of mitochondrial chaperones and proteases. In parallel, cholesterol impaired mitophagy by disrupting autophagic flux, leading to the accumulation of damaged mitochondria. This was accompanied by increased cytosolic mitochondrial DNA (mtDNA), caspase 1 activation, and interleukin-1β secretion. These findings indicate that impaired mitochondrial clearance promotes mtDNA release, thereby linking mitochondrial dysfunction to inflammasome activation. Collectively, cholesterol overload disrupts UPRmt and mitophagy, thereby promoting mitochondrial dysfunction, inflammasome activation, and neuronal apoptosis.

Keywords:  Apoptosis; Cholesterol; Inflammasome; Mitochondria; Mitophagy; SH-SY5Y cells; UPRmt

DOI:  https://doi.org/10.1016/j.fct.2026.116106
Phytomedicine. 2026 Apr 10. pii: S0944-7113(26)00408-3. [Epub ahead of print]155 158174

Spermidine alleviates sepsis-induced cardiomyopathy by improving mitochondrial quality and quantity via a Metallothionein 1-dependent antioxidant pathway.

Shiyun Long, Jiaxin Sun, Yaguang Wu, Jia Yi, Shuang Ren, Xiaoping Ran, Xiaofeng Li, Gautam Sethi, Zhenchun Luo, Chenyang Duan.

   BACKGROUND: Sepsis-induced cardiomyopathy (SICM) is characterized by mitochondrial dysfunction, impaired mitophagic flux, and overwhelming oxidative stress. Spermidine (SPD), a natural polyamine known to enhance autophagy and preserve cardiac function in aging and metabolic disorders, has not been systematically evaluated in the context of septic cardiomyopathy.
PURPOSE: To determine the therapeutic potential and mechanistic basis of SPD in septic cardiac dysfunction.
METHODS: Network pharmacology, RNA sequencing, a cecal ligation and puncture (CLP) mouse model, and multiple cellular assays were integrated to assess the protective actions of SPD. Mitochondrial function, mitophagy flux, and oxidative stress were evaluated using transmission electron microscopy (TEM), immunohistochemistry (IHC), Western blotting, structured illumination microscopy (SIM), mitochondrial membrane potential assays, oxygen consumption rate (OCR) analysis, and mitochondrial DNA (mtDNA) quantification. Transcriptomic clustering and pathway enrichment identified molecular targets, which were validated through siRNA-mediated gene silencing.
RESULTS: SPD markedly attenuated SICM in vivo and in vitro by improving both mitochondrial quantity and quality. It restored sepsis-impaired mitophagy by upregulating LC3B and ATG7, promoting autophagosome maturation, and enhancing cellular ubiquitination. Transcriptomic profiling highlighted metallothionein-1 (MT1) as a key node in metal-ion response pathways. SPD activated the NRF2-MT1-SOD2 antioxidant axis, reduced mitochondrial reactive oxygen species (mtROS) under lipopolysaccharide (LPS) stimulation, and reversed sepsis-induced suppression of SOD2. MT1 knockdown abolished SPD-mediated SOD2 stabilization and mtROS clearance, confirming its essential role in SPD's cardioprotective effects.
CONCLUSION: SPD mitigates SICM by orchestrating the restoration of mitochondrial quality control, normalization of mitophagic flux, and stabilization of cellular redox homeostasis. These findings support SPD as a promising therapeutic candidate for septic cardiomyopathy.

Keywords:  Autophagy; MT1; Mitochondria; ROS; Sepsis; Spermidine

DOI:  https://doi.org/10.1016/j.phymed.2026.158174
Biol Psychiatry. 2026 Apr 21. pii: S0006-3223(26)01190-X. [Epub ahead of print]

Early Life Adversity and Mitochondrial Function: Comparing Cumulative Risk and Dimensional Models of Adversity.

Shiloh Cleveland, Judith E Carroll, Amanda K Montoya, Leah Cha, Linsey Stiles, Jennifer A Sumner.

   BACKGROUND: Early life adversity (ELA) is linked to adverse mental and physical health across the lifespan. One key, yet understudied, mechanism that may be relevant for understanding how ELA becomes biologically embedded is mitochondrial function. Mitochondria are targets of the stress response and mediate stress-related pathology, and impaired mitochondrial function is associated with adverse mental and physical health. However, little clinical research has examined ELA and mitochondrial function. We investigated associations of ELA-operationalized by two prominent conceptual models (cumulative risk and threat-deprivation dimensions)-with mitochondrial function metrics in a community-based sample of trauma-exposed adults.
METHODS: Participants (N=143, 55.9% female) reported on ELA experiences, used to create composites for cumulative ELA and threat- and deprivation-related dimensions. Indices of mitochondrial bioenergetics (oxygen consumption rate, extracellular acidification rate) of live peripheral blood mononuclear cells were assessed with the Agilent Seahorse X96 Extracellular Flux Analyzer. Generalized estimating equations were used to examine associations between cumulative ELA and threat- and deprivation-related dimensions with mitochondrial bioenergetic parameters, adjusting for demographic and technical variables.
RESULTS: Greater cumulative ELA was associated with lower proton leak and ATP production rate from glycolysis, and greater maximal respiration and reserve capacity. Dimensional analyses revealed unique and nuanced associations between threat- and deprivation-related ELA with mitochondrial parameters.
CONCLUSIONS: As the first study to examine cumulative risk and dimensional models of ELA in relation to mitochondrial function, we shed light on distinct impacts of cumulative ELA and threat- and deprivation-related experiences, highlighting an overall pattern of greater respiratory capacity associated with ELA.

Keywords:  Abuse; Deprivation; Extracellular acidification rate; Neglect; Oxygen consumption rate; Threat

DOI:  https://doi.org/10.1016/j.biopsych.2026.04.006
Biol Trace Elem Res. 2026 Apr 22.

The Role of Metal Ions in Mitochondria: From Energy Metabolism to Cell Destiny.

Chunlan Li, Hongpeng Liu, Qiuyue Mao, Jing Fu, Yu Yin, Lijuan Zhu, Kunrong Li, Rui Li, Pengyue Zhang.

  Metal ions are indispensable for cellular life, as they maintain mitochondrial ion homeostasis and function as essential cofactors in mitochondrial energy metabolism, particularly within the electron transport chain (ETC) and the tricarboxylic acid (TCA) cycle. Disruption of metal ion homeostasis, however, can precipitate excessive reactive oxygen species (ROS) generation, collapse of the mitochondrial membrane potential (ΔΨm), and failure of cellular energy supply. These events ultimately culminate in mitochondrial dysfunction and trigger multiple metal ion-dependent cell death pathways, including ferroptosis, copper-induced cell death, and sodium-dependent cell death. By integrating recent advances in metallomics and mitochondrial biology, this review summarizes the roles of six key metal ions-iron (Fe2+), copper (Cu+), sodium (Na+), calcium (Ca2+), zinc (Zn2+), and magnesium (Mg2+)-in mitochondrial energy metabolism and the regulation of cell fate. Emerging evidence indicates that metal ions are not merely metabolic cofactors but also act as critical signalling switches that determine cellular survival or death through modulation of mitochondrial bioenergetics, redox balance, and ion homeostasis. A deeper understanding of metal ion-dependent mitochondrial dysfunction and associated cell death mechanisms provides a robust theoretical framework for elucidating the pathogenesis of cancer, neurodegenerative disorders, and cardiovascular diseases, and may facilitate the development of novel therapeutic strategies targeting mitochondrial metal ion homeostasis.

Keywords:  Adenosine triphosphate; Electron transport chain; Metal ions; Reactive oxygen species; Tricarboxylic acid cycle

DOI:  https://doi.org/10.1007/s12011-026-05112-7
J Pharm Anal. 2026 Apr;16(4): 101452

Role of oxidative stress in sepsis: Mechanisms, pathways, and therapeutic strategies.

Xin-Ru Yang, Ri Wen, Ni Yang, Yang Gao, Tie-Ning Zhang.

  Sepsis, a life-threatening condition caused by dysregulated host response to infection, leads to high morbidity and mortality, primarily due to sepsis-induced organ dysfunction. Oxidative stress, driven by excessive reactive oxygen species (ROS), plays a central role in sepsis pathophysiology, exacerbating inflammation, mitochondrial dysfunction, and cellular damage in multiple organs, including the heart, kidneys, liver, lungs, brain, and skeletal muscles. This review provides a comprehensive analysis of mechanisms by which oxidative stress contributes to sepsis-induced organ injury. Most current research examining the interplay between ROS, inflammation, mitochondrial dysfunction, and cell death pathways such as apoptosis, ferroptosis, and pyroptosis, are animal- or cell-based. Key signaling pathways, including nuclear factor κB (NF-κB), NLR family pyrin domain-containing 3 inflammasome (NLRP3), nuclear factor erythroid 2-related factor 2 (Nrf-2)/heme oxygenase-1 (HO-1), and phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt), are explored as potential therapeutic targets. This review also highlights the roles of mitochondrial quality control (MQC), autophagy, and noncoding RNAs in mitigating oxidative damage.

Keywords:  Mitochondrial dysfunction; Organ dysfunction; Oxidative stress; Sepsis

DOI:  https://doi.org/10.1016/j.jpha.2025.101452
Adv Clin Exp Med. 2026 Apr 21.

Benefits and adverse effects of ketogenic diet treatment in pediatric patients with inborn errors of metabolism.

Dorota Wesół-Kucharska, Magdalena Alicja Kaczor, Ewa Ehmke Vel Emczyńska-Seliga.

   BACKGROUND: The ketogenic diet (KD) is an established therapeutic option for epilepsy and selected inborn errors of metabolism (IEMs), particularly glucose transporter type 1 deficiency (GLUT1D) and pyruvate dehydrogenase complex deficiency (PDCD). Increasing evidence suggests broader applications of KD in pediatric metabolic disorders; however, data on its safety and efficacy in heterogeneous IEM populations remain limited.
OBJECTIVES: To evaluate the efficacy, clinical benefits, and adverse effects (AEs) of KD in pediatric patients with various IEMs.
MATERIAL AND METHODS: A retrospective analysis was conducted in pediatric patients with IEMs receiving KD treatment. Patients were categorized into 3 groups: 1) other IEMs (n = 7), 2) mitochondrial diseases (MD) (n = 17), and 3) GLUT1D and PDCD (n = 20). The median age at initiation of KD was 37, 53, and 53 months, respectively, and the median duration of KD treatment was 5, 11, and 55 months in groups 1, 2, and 3.
RESULTS: The KD was associated with clinical benefits in 84% of patients. Among children with epilepsy (n = 23), a seizure reduction of >50% was observed in 73.9% of patients, including complete seizure freedom in 4 individuals. Improvements were also noted in muscle tone (27.6%), exercise tolerance (51.2%), ataxia (83.3%), and involuntary movements (60%). Lactate levels decreased in 84.6% of patients with mitochondrial disease and in all patients with PDCD. The KD was discontinued in 12 patients due to insufficient efficacy (n = 5) or AEs (AEs; n = 7). The most common AEs included gastrointestinal (GI) symptoms, dyslipidemia, hyperuricemia, metabolic acidosis, and decreased free carnitine; most were transient. No significant association was found between median β-hydroxybutyrate (BHB) levels and clinical outcomes.
CONCLUSIONS: The KD is an effective and generally well-tolerated therapeutic option in pediatric IEMs, with benefits extending beyond seizure control. Adverse effects are typically manageable, although GI intolerance may limit long-term use. Ketogenic diet should be considered not only for refractory epilepsy but also for selected metabolic indications.

Keywords:  epilepsy; inborn errors of metabolism; ketogenic diet; mitochondrial diseases; pediatric metabolic disorders

DOI:  https://doi.org/10.17219/acem/219994
Ann Clin Transl Neurol. 2026 Apr 25.

RNA Sequencing Resolves Cryptic Pathogenic Variants in Mitochondrial Disease.

Zhimei Liu, Xin Duan, Fatemeh Peymani, Jia Wang, Chengjia Bao, Chaolong Xu, Ying Zou, Zixuan Zhang, Yunxi Zhang, Tongyue Li, Martin Pavlov, Junling Wang, Minhan Song, Tianyu Song, Xiaodi Han, Mingxi Sun, Danmin Shen, Ruoyu Duan, Huafang Jiang, Manting Xu, Holger Prokisch, Fang Fang.

   OBJECTIVE: Mitochondrial diseases are the most common inherited metabolic disorders, characterized by pronounced clinical and genetic heterogeneity that complicates molecular diagnosis. Although DNA-based sequencing approaches have become standard in genetic testing, up to half of patients remain without a definitive diagnosis. We aimed to perform RNA sequencing (RNA-seq) of patient-derived skin fibroblasts to enhance the molecular diagnostic efficacy of mitochondrial disease in undiagnosed cases in China.
METHODS: We performed RNA-seq on skin fibroblasts from 140 pediatric patients with suspected mitochondrial disease who remained genetically undiagnosed after whole exome sequencing (WES). Aberrant RNA expression and splicing were identified using the detection of RNA outliers pipeline (DROP). Based on WES findings, patients were stratified into a candidate group (n = 28), in which RNA-seq evaluated the pathogenicity of WES-identified variants of uncertain significance and an unsolved group (n = 112), in which RNA-seq was used to pinpoint candidate genes. In six cases where RNA-seq identified the aberrant RNA event but WES did not detect the causative variants, whole genome sequencing (WGS) was performed.
RESULTS: Integrative RNA-seq, WES, and WGS analysis resulted in a genetic diagnosis in 25% of patients overall (20/28 [71%] in the candidate group; 15/112 [13%] in the unsolved group). Aberrant splicing explained most candidate-group diagnoses, including variants misclassified by in silico predictors such as SpliceAI. 14% of protein-truncating variants predicted to undergo nonsense-mediated decay (NMD) escaped degradation, highlighting the functional limits of current predictions. The variants identified in the unsolved cohort included synonymous, missense, deep intronic, near-splice-site variants, and large deletions. The most frequent among them was a recurrent synonymous East Asian founder mutation in ECHS1, accounting for seven cases. Interestingly, across 233 pathogenic variants associated with aberrant RNA phenotypes compiled from this study and prior reports, half were noncoding and half were coding variants.
CONCLUSION: RNA-seq substantially enhances molecular diagnosis in mitochondrial disease by exposing cryptic splicing, regulatory, and NMD-escape events invisible to DNA sequencing alone. These data advocate transcriptome analysis as an essential component of comprehensive genomic diagnostics in neurometabolic disease.

Keywords:  RNA sequencing; mitochondrial diseases; pediatric; whole‐exome sequencing; whole‐genome sequencing

DOI:  https://doi.org/10.1002/acn3.70379
J Inherit Metab Dis. 2026 May;49(3): e70184

Aminoacyl-tRNA Synthetases: Variant Classification, Functional Assays, and Emerging Therapeutic Strategies.

M I Mendes, D E Smith, V Spek, A M Bosch, W E Corpeleijn, M Engelen, S A Fuchs, A Hadchouel, I U Heinemann, R H Houtkooper, E M M Hoytema van Konijnenburg, S Kemp, M Langeveld, C D M Karnebeek, A Pop, V M Siu, N I Wolf, G S Salomons.

Aminoacyl-tRNA synthetases (aaRS) are essential enzymes that charge tRNAs with their corresponding amino acids, playing a critical role in protein synthesis. All 37 nuclear-encoded ARS genes, comprising both cytosolic (ARS1) and mitochondrial (ARS2) isoforms, have now been linked to human disease. Pathogenic variants in these genes cause a wide range of phenotypes, from dominant peripheral neuropathies to recessive multisystemic disorders. Despite the high number of ARS variants identified, functional validation remains difficult, with over 80% of missense variants classified as VUS in public databases. Additionally, the role of non-canonical aaRS functions in disease remains an area requiring further exploration. Our laboratory developed a high-throughput LC-MS/MS-based aminoacylation assay to measure aaRS activity in patient-derived fibroblasts, aiding in variant classification. This functional approach has contributed to the diagnosis of nearly 200 patients and has uncovered complex variant effects, including thermolabile and splicing-defective forms. Therapeutically, amino acid supplementation and dietary interventions have shown effect in select cases, while gene therapy is being explored for dominant ARS-related neuropathies. Amenability to targeted interventions further underlines the need for correct interpretation of genetic variants, which are increasingly recognized as genetic testing is progressively used in the diagnostic work-up and functional assays. Additionally, natural history studies are essential to improve diagnosis, understand disease mechanisms, and guide and evaluate personalized treatment. This review underscores the critical need for integrated genomic and functional approaches to advance variant interpretation and therapeutic development in the era of NGS.

DOI: https://doi.org/10.1002/jimd.70184