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Evaluating the feasibility of gene replacement strategies to treat MTRFR deficiency.
Full text linkMitochondrial translation release factor in rescue (MTRFR) catalyzes a termination step in protein synthesis, facilitating release of the nascent chain from mitoribosomes. Pathogenic variants in MTRFR cause MTRFR deficiency and are loss-of-function variants. Here, we tested gene replacement as a possible therapeutic strategy. A truncating mutation (K155*) was generated in mice; however, homozygotes die embryonically whereas mice heterozygous for this K155* allele are normal. We also generated transgenic strains expressing either wild-type human MTRFR or a partially functional MTRFR. Despite dose-dependent phenotypes from overexpression in vitro, neither transgene caused adverse effects in vivo. In K155* homozygous mice, the wild-type MTRFR transgene completely rescued the phenotype with only one copy present, whereas the mutant transgene rescued less efficiently. Detailed evaluation of mice rescued with the wild-type MTRFR transgene revealed no abnormalities. In human induced pluripotent stem cell (hiPSC)-derived knockdown neurons, mitochondrial phenotypes were corrected by AAV9-mediated delivery of MTRFR. Thus, we find no toxicity from truncated gene products or overexpression of MTRFR in vivo, and expression of MTRFR corrects phenotypes in both mouse and hiPSC models
Mitochondrial complex I deficiency induces Alzheimer\u27s disease-like signatures that are reversible by targeted therapy.
Full text linkINTRODUCTION: Mitochondrial dysfunction is implicated in Alzheimer\u27s disease (AD), but whether it drives AD-associated changes is unclear. We assessed transcriptomic alterations in the brains of Ndufs4
METHODS: Cortico-hippocampal tissue from Ndufs4
RESULTS: Knockout of Ndufs4-mediated mtCI deficiency disrupted mitochondrial homeostasis, energy metabolism, and synaptic gene expression, recapitulating transcriptomic signatures of AD. CP2 treatment partially reversed these changes, with female Ndufs4
DISCUSSION: Loss of mtCI activity alone is sufficient to induce AD-like molecular changes in the brain, independent of amyloid beta or phosphorylated tau. CP2-mediated rescue highlights the potential of targeting mitochondria as a therapeutic strategy for AD. Sex-specific responses suggest important considerations for personalized therapeutics.
HIGHLIGHTS: Activity of mitochondrial complex I (mtCI) affects broad mitochondrial and neuronal transcriptional networks. A reduction of mtCI activity is sufficient to induce transcriptomic changes reminiscent of those observed in late-onset Alsheimer\u27s disease (AD) patients and familial mouse models of AD. Pharmacological targeting of mtCI mediates neuroprotective signaling. Male and female mice have differential responses to the loss of mtCI activity and to the mitochondria-targeted therapeutics. Mitochondria play a key role in AD development and treatment
LONP1 regulation of mitochondrial protein folding provides insight into beta cell failure in type 2 diabetes.
Full text linkProtein misfolding is a contributor to the development of type 2 diabetes (T2D), but the specific role of impaired proteostasis is unclear. Here we show a robust accumulation of misfolded proteins in the mitochondria of human pancreatic islets from patients with T2D and elucidate its impact on β cell viability through the mitochondrial matrix protease LONP1. Quantitative proteomics studies of protein aggregates reveal that islets from donors with T2D have a signature resembling mitochondrial rather than endoplasmic reticulum protein misfolding. Loss of LONP1, a vital component of the mitochondrial proteostatic machinery, with reduced expression in the β cells of donors with T2D, yields mitochondrial protein misfolding and reduced respiratory function, leading to β cell apoptosis and hyperglycaemia. LONP1 gain of function ameliorates mitochondrial protein misfolding and restores human β cell survival after glucolipotoxicity via a protease-independent effect requiring LONP1-mitochondrial HSP70 chaperone activity. Thus, LONP1 promotes β cell survival and prevents hyperglycaemia by facilitating mitochondrial protein folding. These observations provide insights into the nature of proteotoxicity that promotes β cell loss during the pathogenesis of T2D, which could be considered as future therapeutic targets
Sustained Lung Inflammation Post-SARS-CoV-2 Infection in Mice Is Associated with Increased Pulmonary T Cells.
Full text linkMany SARS-CoV-2 patients experience chronic pulmonary symptoms and long-term inflammation despite viral clearance. While these clinical manifestations have been linked to the dysregulation of the adaptive immune response, the underlying immunopathology remains poorly understood due to a lack of suitable animal models. To investigate long-term pulmonary consequences of SARS-CoV-2 infection, we used a genetic cross of 129 mice and C57BL/6 (B6)-K18-hACE2 transgene mice, a model previously shown to survive infection. 129xB6-K18-hACE2 mice or littermate controls were infected with a low dose (5 × 102 PFU) of ancestral SARS-CoV-2. Complete viral clearance and full recovery from weight loss occurred by day 8 post-infection. However, prolonged inflammation in the lung and airways persisted up to day 28 post-infection and was associated with the presence of CD4+ and CD8+ T cells, particularly CD8+ effector T cells. This model may therefore prove valuable for further understanding of drivers of long-term lung inflammation and for testing therapeutic strategies and clinically relevant interventions that can target long-term pulmonary inflammation following SARS-CoV-2 infection
Gut metagenomes reveal interactions between dietary restriction, ageing and the microbiome in genetically diverse mice.
No full textThe gut microbiome changes with age and has been proposed to mediate the benefit of lifespan-extending interventions such as dietary restriction. However, the causes and consequences of microbiome ageing and the potential of such interventions remain unclear. Here we analysed 2,997 metagenomes collected longitudinally from 913 deeply phenotyped, genetically diverse mice to investigate interactions between the microbiome, ageing, dietary restriction (caloric restriction and fasting), host genetics and a range of health parameters. Among the numerous age-associated microbiome changes that we find in this cohort, increased microbiome uniqueness is the most consistent parameter across a second longitudinal mouse experiment that we performed on inbred mice and a compendium of 4,101 human metagenomes. Furthermore, cohousing experiments show that age-associated microbiome changes may be caused by an accumulation of stochastic environmental exposures (neutral theory) rather than by the influence of an ageing host (selection theory). Unexpectedly, the majority of taxonomic and functional microbiome features show small but significant heritability, and the amount of variation explained by host genetics is similar to ageing and dietary restriction. We also find that more intense dietary interventions lead to larger microbiome changes and that dietary restriction does not rejuvenate the microbiome. Lastly, we find that the microbiome is associated with multiple health parameters, including body composition, immune components and frailty, but not lifespan. Overall, this study sheds light on the factors influencing microbiome ageing and aspects of host physiology modulated by the microbiome
Systematic Ocular Phenotyping of Knockout Mouse Lines Identifies Genes Associated With Age-Related Corneal Dystrophies.
Full text linkPURPOSE: This study investigates genes contributing to late-adult corneal dystrophies (LACDs) in aged mice, with potential implications for late-onset corneal dystrophies (CDs) in humans.
METHODS: The International Mouse Phenotyping Consortium (IMPC) database, containing data from 8901 knockout mouse lines, was filtered to include late-adult mice (49+ weeks) with significant (P \u3c 0.0001) CD phenotypes. Candidate genes were mapped to human orthologs using the Mouse Genome Informatics group, with expression analyzed via PLAE and a literature review for prior CD associations. Comparative analyses of LACD genes from IMPC and established human CD genes from IC3D included protein interactions (STRING), biological processes (PANTHER), and molecular pathways (KEGG).
RESULTS: Analysis identified 14 genes linked to late-adult abnormal corneal phenotypes. Of these, 2 genes were previously associated with CDs in humans, while 12 were novel. Seven of the 14 genes (50%) were expressed in the human cornea based on single-cell transcriptomics. Protein-protein interactions via STRING showed several significant interactions with known human CD genes. PANTHER analysis identified six biological processes shared with established human CD genes. Two genes (Rgs2 and Galnt9) were involved in pathways related to human corneal diseases, including cGMP-PKG signaling, mucin-type O-glycan biosynthesis, and oxytocin signaling. Other candidates were implicated in pathways such as pluripotency of stem cells, MAPK signaling, WNT signaling, actin cytoskeleton regulation, and cellular senescence.
CONCLUSIONS: This study identified 14 genes linked to LACD in knockout mice, 12 of which are novel in corneal biology. These genes may serve as potential therapeutic targets for treating corneal diseases in aging human populations
Merritt-Putnam Symposium | Developmental and Epileptic Encephalopathies-Current Concepts and Novel Approaches.
Full text linkDevelopmental and epileptic encephalopathies (DEEs) are among the most severe and difficult to treat epilepsies. Two broad strategies for understanding the etiology and impacts of DEEs include genetic and complex adaptive systems approaches. This review, inspired by the 2024 Merritt-Putnam Symposium, describes current perspectives of DEE, identifies limitations of current views, and discusses potential novel ways forward. First, we discuss the rationale for a reevaluation of the role of seizures in the pathogenesis of cognitive and behavioral impairments in DEE. Second, we discuss newly emerging methods employing neural organoids to study brain development and DEE in vitro. Third, we present recent precision therapy approaches for the clinical treatment of DEE. Lastly, we discuss computational systems approaches to understanding the genetic landscape of DEE. The severe and multifaceted impacts of DEE and associated comorbidities underscore the necessity of novel interdisciplinary approaches to produce an improved understanding of etiology and more effective treatment strategies
Human Phenotype Ontology Annotations for Rare Congenital Conditions: Application to Arthrogryposis Multiplex Congenita.
No full textArthrogryposis multiplex congenita (AMC) represents a large, rare group of congenital conditions. This study addressed major challenges in AMC research posed by the lack of systematic frameworks for data collection and the use of inconsistent terminologies and text descriptions. We aimed to systematically review the Human Phenotype Ontology (HPO) terms, encode AMC phenotypic traits as HPO terms, and pilot test the encoding process in a cohort of children with AMC. An international consensus-based dataset for AMC was used to extract phenotypic traits from the fetal period to adulthood. The encoding process was developed by an international expert panel to expand and revise HPO ontology for joint contractures, as the main characterizing traits in AMC. Using a pre-tested mapping algorithm, the HPO mapping process resulted in a 62% complete match, a 12% incomplete match, and a 26% no match. The encoding process included 37 new terms and annotations and 13 re-structures across 10 different joints. The implemented annotations significantly increased the number of available HPO terms for joint contractures in a cohort of children with AMC (p-value = 0.04). Our encoding and annotation approach may be used as a blueprint for systematic HPO (re)annotations for musculoskeletal and non-musculoskeletal phenotypic traits of AMC
Caspase-11 drives macrophage hyperinflammation in models of Polg-related mitochondrial disease.
Full text linkMitochondrial diseases (MtD) represent a significant public health challenge due to their heterogenous clinical presentation, often severe and progressive symptoms, and lack of effective therapies. Environmental exposures, such bacterial and viral infection, can further compromise mitochondrial function and exacerbate the progression of MtD. However, the underlying immune alterations that enhance immunopathology in MtD remain unclear. Here we employ in vitro and in vivo approaches to clarify the molecular and cellular basis for innate immune hyperactivity in models of polymerase gamma (Polg)-related MtD. We reveal that type I interferon (IFN-I)-mediated upregulation of caspase-11 and guanylate-binding proteins (GBP) increase macrophage sensing of the opportunistic microbe Pseudomonas aeruginosa (PA) in Polg mutant mice. Furthermore, we show that excessive cytokine secretion and activation of pyroptotic cell death pathways contribute to lung inflammation and morbidity after infection with PA. Our work provides a mechanistic framework for understanding innate immune dysregulation in MtD and reveals potential targets for limiting infection- and inflammation-related complications in Polg-related MtD
Retinal vascular dysfunction in the Mthfr(677C\u3eT) mouse model of cerebrovascular disease
Full text linkINTRODUCTION: Investigations of retinal biomarkers for Alzheimer\u27s disease (AD) and AD and related dementias (ADRD), has increased significantly. We examine retinal vascular health in a mouse containing the ADRD risk variant Mthfr
METHODS: Morphology and function of retinal vasculature and neurons were assessed using in vivo imaging, immunohistochemistry, and pattern electroretinography. RNAscope and proteomics were employed to determine Mthfr gene expression and differential protein expression in mice carrying Mthfr
RESULTS: Mice show age- and sex-dependent retinal vascular deficits, displaying similarities to previously published brain data. Mthfr is widely expressed and co-localizes with vascular cell markers. Proteomics identified common molecular signatures across the brain and retina.
DISCUSSION: Results demonstrate that Mthfr-dependent vascular phenotypes occur in brain and retina similarly. These data suggest that assessing age and genetic-driven changes within retinal vasculature represents a minimally invasive method to predict AD-related cerebrovascular damage.
HIGHLIGHTS: Mthf