Biology subjects

Kawamata, H.

Publications and source records attributed to Kawamata, H..

9 recordsLinked to original sources

bioRxiv2026

Calcium dysregulation amplifies fibrotic responses to TGFβ in human Friedreich's ataxia fibroblasts

Friedreich's ataxia (FA) is an inherited disease caused by loss of frataxin (FXN) and characterized by neurodegeneration and fatal cardiomyopathy. Cardiac fibrosis contributes to cardiomyopathy by stiffening the heart wall, yet the underlying mechanisms remain unknown. Here, we investigated pro-fibrotic predisposition in FA patient-derived fibroblasts, focusing on the role of cytosolic calcium (Ca) in TGF{beta}-driven fibroblast-to-myofibroblast transition (FMT). We found pro-fibrotic transcriptional priming in FA fibroblasts, alongside elevated expression of genes controlled by the Ca-responsive transcription factor NFAT. Upon FMT, FA myofibroblasts showed amplified induction of pro-fibrotic (CCN2, NOX4) and suppression of anti-fibrotic (CCN3) genes, which were inversely correlated with residual FXN. Mechanistically, FA fibroblasts exhibited elevated cytosolic Ca and strongly downregulated expression of the Na-Ca exchanger NCX1, which directly correlated with FXN. Furthermore, NCX1 inhibition in control fibroblasts recapitulated FA Ca phenotypes, whereas NCX1 transduction in FA fibroblasts normalized Ca dynamics and blunted CCN2 induction in FMT. These findings highlight NCX1 as a modulator of fibrotic reprogramming in FA and identify Ca dyshomeostasis as an intrinsic mechanism of fibrosis that could be targeted therapeutically.

molecular biology↗

bioRxiv2025

A mouse model of CHCHD10 p.R15L familial ALS presents mild, age-related motor neuron degeneration without protein instability or mitochondrial dysfunction

Mutations in the mitochondrial protein CHCHD10 (D10) cause a spectrum of hereditary neurodegenerative disorders. Among these, the p.R15L variant is linked to a slowly progressive, late-onset familial form of amyotrophic lateral sclerosis (ALS) with unclear pathogenic mechanisms. To better understand this, we investigated a knock-in (KI) mouse model carrying the p.R15L mutation in the endogenous protein. Unlike previously described mutant D10 KI models, p.R15L KI mice exhibited normal D10 protein levels, with no evidence of large protein aggregates. Mitochondrial respiration and hydrogen peroxide emission in mitochondria isolated from muscle and brain were unaltered. Similarly, fibroblasts from human p.R15L carriers exhibited normal D10 levels and unchanged oxidative phosphorylation function. Histochemical analyses of p.R15L KI muscle revealed mild increases in mitochondrial enzymatic activity in a subset of muscle fibers and muscle transcriptomics showed elevated expression of PGC-1, suggesting enhanced mitochondrial biogenesis. p.R15L KI mice developed subtle, late-onset phenotypes, including reduced body weight and motor activity and increased anxiety-like behavior. Importantly, in aged mice electrophysiological studies demonstrated decreased amplitude of the compound muscle action potential, commensurate with a moderate loss of spinal cord motor neurons and elevated serum neurofilament light levels, indicative of neurodegeneration. Together, these results indicate that the p.R15L mutation produces a mild, late-onset motor neuron phenotype in mice, partially recapitulating the human disease, without mitochondrial functional or morphological alterations. The findings indicate that p.R15L D10 selectively impairs mouse motor neurons through a gain-of-function mechanism, providing a genetically accurate yet mild in vivo model of familial ALS.

neuroscience↗

bioRxiv2025

Investigation of mitochondrial phenotypes in motor neurons derived by direct conversion of fibroblasts from familial ALS subjects

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease of motor neurons, leading to fatal muscle paralysis. Familial forms of ALS (fALS) account for approximately 10% of cases and are associated with mutations in numerous genes. Alterations of mitochondrial functions have been proposed to contribute to disease pathogenesis. Here, we employed a direct conversion (DC) technique to generate induced motor neurons (iMN) from skin fibroblasts to investigate mitochondrial phenotypes in a patient-derived disease relevant cell culture system. We converted 7 control fibroblast lines and 17 lines harboring the following fALS mutations, SOD1A4V, TDP-43N352S, FUSR521G, CHCHD10R15L, and C9orf72 repeat expansion. We developed new machine learning approaches to identify iMN, analyze their mitochondrial function, and follow their fate longitudinally. Mitochondrial and energetic abnormalities were observed, but not all fALS iMN lines exhibited the same alterations. SOD1A4V, C9orf72, and TDP-43N352S iMN had increased mitochondrial membrane potential, while in CHCHD10R15L cells membrane potential was decreased. TDP-43N352S iMN displayed changes in mitochondrial morphology and increased motility. SOD1A4V, TDP-43N352S, and CHCHD10R15L iMN had increased oxygen consumption rates and altered extracellular acidification rates, reflecting a hypermetabolic state similar to the one described in sporadic ALS fibroblasts. FUSR521G mutants had decreased ATP/ADP ratio, suggesting impaired energy metabolism. We then tested the viability of iMN and found decreases in survival in SOD1A4V, C9orf72, and FUSR521G, which were corrected by small molecules that target mitochondrial stress. Together, our findings reinforce the role of mitochondrial dysfunction in ALS and indicate that fibroblast-derived iMN may be useful to study fALS metabolic alterations. Strengths of the DC iMN approach include low cost, speed of transformation, and the preservation of epigenetic modifications. However, further refinement of the fibroblasts DC iMN technique is still needed to improve transformation efficiency, reproducibility, the relatively short lifespan of iMN, and the senescence of the parental fibroblasts.

neuroscience↗

bioRxiv2024

Amyloid fibril structures link CHCHD10 and CHCHD2 to neurodegeneration.

CHCHD10 is mutated in rare cases of FTD and ALS and aggregates in mouse models of disease. Here we show that the disordered N-terminal domain of CHCHD10 forms amyloid fibrils and report their cryoEM structure. Disease-associated mutations cannot be accommodated by the WT fibril structure, while sequence differences between CHCHD10 and CHCHD2 are tolerated, explaining the co-aggregation of the two proteins and linking CHCHD10 and CHCHD2 amyloid fibrils to neurodegeneration.

biophysics↗

bioRxiv2023

Glucose Hypometabolism Prompts RAN Translation and Exacerbates C9orf72-related ALS/FTD Phenotypes

The most prevalent genetic cause of both amyotrophic lateral sclerosis and frontotemporal dementia is a (GGGGCC)n nucleotide repeat expansion (NRE) occurring in the first intron of the C9orf72 gene (C9). Brain glucose hypometabolism is consistently observed in C9-NRE carriers, even at pre-symptomatic stages, although its potential role in disease pathogenesis is unknown. Here, we identified alterations in glucose metabolic pathways and ATP levels in the brain of asymptomatic C9-BAC mice. We found that, through activation of the GCN2 kinase, glucose hypometabolism drives the production of dipeptide repeat proteins (DPRs), impairs the survival of C9 patient-derived neurons, and triggers motor dysfunction in C9-BAC mice. We also found that one of the arginine-rich DPRs (PR) can directly contribute to glucose metabolism and metabolic stress. These findings provide a mechanistic link between energy imbalances and C9-ALS/FTD pathogenesis and support a feedforward loop model that opens several opportunities for therapeutic intervention.

neuroscience↗

bioRxiv2023

High fat diet ameliorates the mitochondrial cardiomyopathy of CHCHD10 mutant mice

Mutations in CHCHD10, a mitochondrial protein with undefined functions, are associated with autosomal dominant mitochondrial diseases. Chchd10 knock-in mice harboring a heterozygous S55L mutation (equivalent to human pathogenic S59L) develop a fatal mitochondrial cardiomyopathy caused by CHCHD10 aggregation and proteotoxic mitochondrial integrated stress response (mtISR). In mutant hearts, mtISR is accompanied by a metabolic rewiring characterized by increased reliance on glycolysis rather than fatty acid oxidation. To counteract this metabolic rewiring, heterozygous S55L mice were subjected to chronic high fat diet (HFD) to decrease insulin sensitivity and glucose uptake and enhance fatty acid utilization in the heart. HFD ameliorated the ventricular dysfunction of mutant hearts and significantly extended the survival of mutant female mice affected by severe pregnancy-induced cardiomyopathy. Gene expression profiles confirmed that HFD increased fatty acid utilization and ameliorated cardiomyopathy markers. Importantly, HFD also decreased accumulation of aggregated CHCHD10 in the S55L heart, suggesting activation of quality control mechanisms. Overall, our findings indicate that metabolic therapy can be effective in mitochondrial cardiomyopathies associated with proteotoxic stress.

molecular biology↗

bioRxiv2022

Effects of the investigational drug sodium phenylbutyrate-TUDCA (AMX0035) on the transcriptional and metabolic landscape of sporadic ALS fibroblasts

ALS is a rapidly progressive, fatal disorder caused by motor neuron degeneration, for which there is a great unmet therapeutic need. AMX0035, a combination of sodium phenylbutyrate (PB) and taurursodiol (TUDCA, Turso), has shown promising results in early ALS clinical trials, but its mechanisms of action remain to be elucidated. To obtain an unbiased landscape of AMX0035 effects we investigated the transcriptomic and metabolomic profiles of primary skin fibroblasts from sporadic ALS patients and healthy controls treated with PB, TUDCA, or PB-TUDCA combination (Combo). Combo changed many more genes and metabolites than either PB or TUDCA individually. Most changes were unique to Combo and affected the expression of genes involved in ALS-relevant pathways, such as nucleocytoplasmic transport, unfolded protein response, mitochondrial function, RNA metabolism, and innate immunity. Weighted gene coexpression network analysis showed that significant correlations between ALS gene expression modules and clinical parameters were abolished by Combo. This study is the first to explore the molecular effects of Combo in ALS patient-derived cells. It shows that Combo has a greater and distinct impact compared to the individual compounds and provides clues to drug targets and mechanisms of actions, which may underlie the benefits of this investigational drug combination.

neuroscience↗

bioRxiv2019

Accelerated trans-sulfuration metabolically defines a discrete subclass of ALS patients

Amyotrophic lateral sclerosis (ALS) is a disease characterized by progressive paralysis and death. Most ALS cases are sporadic (sALS) and patient heterogeneity poses a formidable challenge for the development of viable biomarkers and effective therapies. Applying untargeted metabolite profiling on 77 sALS patient-derived primary dermal fibroblast lines and 45 sex/age matched controls, we found that [~]25% of cell lines (termed sALS-1) are characterized by upregulated trans-sulfuration, where methionine-derived homocysteine is channeled into cysteine and glutathione synthesis. sALS-1 fibroblasts exhibit a growth defect when grown under oxidative conditions, that can be fully-rescued by N-acetylcysteine. [U-13C]-glucose tracing shows that activation of the trans-sulfuration pathway is associated with accelerated glucose flux into the TCA cycle. Based on four metabolites, we developed a support vector machine model capable of distinguishing sALS-1 with 97.5% accuracy. Importantly, plasma metabolite profiling identifies a systemic perturbation of cysteine metabolism as a hallmark of sALS-1. These results indicate that sALS patients can be stratified into distinct metabotypes, differently sensitive to metabolic stress, and provides new insights into metabolic biomarkers for personalized sALS therapy.

neuroscience↗

bioRxiv2018

Identification of a Distinct Metabolomic Subtype of Sporadic ALS Patients

Sporadic amyotrophic lateral sclerosis (sALS) is a progressive motor neuron disease resulting in paralysis and death. Genes responsible for familial ALS have been identified, however the molecular basis for sALS is unknown. To discover metabotypic biomarkers that inform on disease etiology, untargeted metabolite profiling was performed on 77 patient-derived dermal fibroblast lines and 45 age/sex-matched controls. Surprisingly, 25% of sALS lines showed upregulated methionine-derived homocysteine, channeled to cysteine and glutathione (GSH). Stable isotope tracing of [U-13C]-glucose showed activation of the trans-sulfuration pathway, associated with accelerated glucose flux into the TCA cycle, glutamate, GSH, alanine, aspartate, acylcarnitines and nucleotide phosphates. A four-molecule support vector machine model distinguished the sALS subtype from controls with 97.5% accuracy. Plasma metabolite profiling identified increased taurine as a hallmark metabolite for this sALS subset, suggesting systemic perturbation of cysteine metabolism. Furthermore, integrated multiomics (mRNAs/microRNAs/metabolites) identified the super-trans-sulfuration pathway as a top hit for the sALS subtype. We conclude that sALS can be stratified into distinct metabotypes, providing for future development of personalized therapies that offer new hope to sufferers.

neuroscience↗