Biology subjects

Puccio, H.

Publications and source records attributed to Puccio, H..

9 recordsLinked to original sources

bioRxiv2026

TLR4-mediated neuroimmune signalling drives proprioceptive neuron degeneration in Friedreich ataxia

Friedreich ataxia (FA) is one of the most common inherited autosomal recessive neurodegenerative disorder, caused by a GAA repeat expansion in the FXN gene, leading to frataxin deficiency and progressive sensory and spinocerebellar ataxia. FA is characterized by selective vulnerability of proprioceptive sensory neurons (pSNs) in the dorsal root ganglia (DRG), which are major contributors to sensory ataxia. Despite the central role of mitochondrial dysfunction in FA, the mechanisms that drives the neuronal loss remains unclear. Here, we show that metabolic stress in sensory neurons elicits a neuroimmune response in surrounding tissue, revealing a non-cell-autonomous mechanism of disease progression. We identify Toll-like receptor 4 (TLR4) signaling as a key link between neuronal dysfunction and inflammatory response. Inhibition of TLR4 reduces cellular stress, restores neuronal integrity, and delays disease progression in vivo. These findings redefine FA as a disorder involving neuroimmune crosstalk and highlight TLR4 signaling as a potential therapeutic target.

neuroscience↗

bioRxiv2025

Frataxin depletion leads to decreased soma size and activation of AMPK metabolic pathway in dorsal root ganglia sensory neurons

IntroductionFriedreichs ataxia (FA) is an inherited neurodegenerative disorder caused by frataxin deficiency, leading to impaired iron-sulfur (Fe-S) cluster biogenesis and mitochondrial dysfunction. Proprioceptive dorsal root ganglia (DRG) neurons are among the most vulnerable cell types in FA, yet the mechanisms underlying their selective susceptibility remain unclear. MethodsWe developed a primary culture model of embryonic mouse DRG neurons with complete frataxin depletion, enabling longitudinal analysis of cellular and metabolic alterations. ResultsThis novel model reproduces several key biochemical hallmarks of FA, including Fe-S enzyme deficiency, mitochondrial dysfunction, altered iron homeostasis and oxidative stress. Despite severe mitochondrial impairment, frataxin-deficient neurons remained viable but exhibited a marked reduction in soma growth. Mechanistically, this phenotype was associated with activation of AMP-activated protein kinase (AMPK) hyperactivation and inhibition of mTOR signaling. Genetics inhibition of AMPK or re-expression of frataxin restored neuronal growth, demonstrating a functional link between metabolic stress signaling and soma size regulation. Treatment with -lipoic acid (ALA) rescued soma growth, normalize ATP levels and reduce AMPK activation. ConclusionsOur findings identify AMPK-mTOR signaling as a key pathway linking mitochondrial dysfunction to impaired neuronal growth impairment in frataxin-deficient sensory neurons. This robust, scalable cellular model provides new insights into sensory neuron vulnerability and offers a platform for therapeutic discovery.

molecular biology↗

bioRxiv2025

Partial Bypass of Frataxin Deficiency by ISCU M141I Restores Cytosolic and Nuclear FeS Cluster Assembly

Iron-sulfur (Fe-S) clusters are essential cofactors required for the activity of numerous proteins involved in fundamental cellular processes, including DNA replication, metabolism and mitochondrial respiration. In eukaryotes, Fe-S cluster biogenesis is initiated in mitochondria by the ISC machinery, which assembles iron and sulfur, delivered by a cysteine desulfurase, onto the scaffold protein ISCU. Frataxin (FXN), a key regulator of this pathway, enhances Fe-S production by accelerating persulfide transfer to ISCU. FXN is essential in eukaryotes, and its loss results in "petite" phenotype in yeast, senescence in dividing mammalian cells and embryonic lethality in mice. Interestingly, in yeast, a methionine to isoleucine substitution at position 141 of the scaffold protein Isu1 can bypass the requirement of FXN. To test whether this bypass mechanism is conserved in mammals, we introduced the equivalent M141I substitution into the endogenous Iscu gene in murine fibroblasts carrying a conditional Fxn allele using CRISPR-Cas9. We show that the ISCU M141I variant enables cell survival in the absence of FXN, preventing cell cycle arrest and decreasing baseline DNA damage. However, these FXN-null survivor clones exhibit slower proliferation, persistent mitochondrial dysfunction and defective mitochondrial Fe-S cluster proteins. In contrast, nuclear and cytosolic Fe-S proteins are preserved, as is cellular iron homeostasis. Importantly, the ISCU M141I variant delays, but does not fully rescue, embryonic lethality in Fxn-deficient mice. Altogether, our results reveal a previously unrecognized compartment-specific rescue of Fe-S cluster dependent processes by the ISCU M141I variant in mammalian cells, raising for the first time the possibility of compartmental regulation of Fe-S cluster biogenesis.

cell biology↗

bioRxiv2025

Characterization of a COQ8A-ataxia mouse model with E548K single-site mutation: distinct and comparable findings relative to a loss-of-function mutation

COQ8A-ataxia, also known as autosomal recessive cerebellar ataxia type 2 (ARCA2), is a rare mitochondrial disorder caused by biallelic mutations in COQ8A, a gene encoding for a mitochondrial protein critical for coenzyme Q (CoQ) biosynthesis. Although there is no clear genotype-phenotype correlation in patients, loss-of function variants generally produce a cerebellar-restricted phenotype, while missense mutations are more frequently associated with multisystemic symptoms. The COQ8AE551K variant has been reported at the homozygous state in individuals with early-onset disease and widespread systemic involvement. This study aimed to characterize the new Coq8aE548K knocking mouse model, equivalent to the human E551K variant, and compare its phenotype to the complete Coq8a-/- knockout mouse. Based on human data and preliminary data in the zebrafish, we hypothesized that the Coq8aE548K knocking would present a more pronounced phenotype than the constitutive knockout. Contrary to our initial hypothesis, mice homozygous for the Coq8aE548K allele exhibited no significant motor or cognitive impairments, nor muscle phenotype. Biochemically, the knocking Coq8aE548K mutation led to variable instability of the COQ8AE548K protein and reduced expression of proteins in the CoQ biosynthesis pathway, such as COQ5 and COQ7 in both cerebellum and muscle, similarly to the constitutive knockout. Despite this, mitochondrial function and tissue architecture remained intact, suggesting preserved cellular resilience. These findings highlight the complexity of genotype-phenotype correlations in COQ8A-related ataxia and provides a tool for investigating sub-threshold mitochondrial dysfunction.

cell biology↗

bioRxiv2024

mitoXplorer 3.0, a web tool for exploring mitochondrial dynamics in single-cell RNA-seq data.

Mitochondria are important eukaryotic organelles, best known for their function in ATP production and in cellular metabolism and signalling. It is widely accepted that their structure, composition and function differ across cell types. However, little is known about mitochondrial variability within the same cell type. To truly understand mitochondrial function and dynamics, we need to study individual cell types, as well as mitochondrial variability on a single-cell level. Based on our mitoXplorer 2.0 web tool, we introduce mitoXplorer 3.0 with new features adapted for analysing single-cell sequencing data, focusing only on mitochondria. We provide a formatting script, scXplorer to generate mitoXplorer 3.0 compatible files for upload. This script creates pseudo-bulk transcriptomes of cell types from scRNA-seq data for differential expression analysis and subsequent mitochondria-centric analysis with mitoXplorer classical interfaces. It also creates a single-cell expression matrix only containing mitochondria-associated genes (mito-genes), which can be analysed for cell-to-cell variability with novel, interactive interfaces created for mitoXplorer 3.0: these new interfaces help to identify sub-clusters of cell types based only on mito-genes and offer in-depth mitochondria-centric analysis of subpopulations. We demonstrate the usability and predictive power of mitoXplorer 3.0 using single-cell transcriptome data from a single-cell study of Spinocerebellar Ataxia Type 1. We identified several mito-processes and mito-genes that are majorly affected in SCA1 Purkinje cells and which might contribute to our understanding of mitochondrial decline and subsequent Purkinje cell loss in this disease. MitoXplorer 3.0 is freely available at https://mitoxplorer3.ibdm.univ-amu.fr.

bioinformatics↗

bioRxiv2024

Frataxin deficiency in proprioceptive neurons is causal to inflammatory and glial responses in dorsal root ganglia

Friedreich ataxia (FA), the most common recessive hereditary ataxia, is an early-onset neurodegenerative disease characterized by pathological changes occurring first in the peripheral dorsal root ganglia (DRG), with loss of the large sensory proprioceptive neurons, leading to ganglionopathy and proprioceptive deficits. FA is caused by a mutation in frataxin gene (Fxn), leading to reduced expression of frataxin protein (FXN), an essential ubiquitous mitochondrial protein. Most research has focused on the pathophysiological involvement of proprioceptors. However, in recent years, neuroinflammation is increasingly recognized as an integral and critical contributor in FA pathogenesis. Furthermore, it has also recently been shown a primary reactivity of satellite glial cells (SGCs; glia tightly enwrapping proprioceptor cell bodies), suggesting a role of inflammation and SGC responses in the destruction of proprioceptors in FA patients DRGs. It remains unclear to what extent the increase in DRG macrophage response and/or SGC reactivity may contribute to FA phenotype. Therefore, it is important to fully study and understand the mechanism of proprioceptor-macrophages-SGC interactions and their regulations. Exploring relationship between these three cell types has profound implications for breaking through the limitation of treatment of FA. Here we asked whether FXN deficiency selectively in DRG proprioceptive neurons is sufficient to cause inflammatory and glial responses found in patients DRG. We used RNA profiling, bioinformatics signaling network and pathway analysis, combined with immunohistochemistry and behavioral experiments to reveal some genes, signaling pathways in macrophages and SGCs that may represent potential biomarkers of the disease. Our study revealed that proprioceptor FXN deficiency causes major changes in inflammatory macrophage and SGC gene transcription as well as macrophage and SGC number, highlighting molecular and cellular pathways that were sequentially altered, thus representing temporal signatures of FA ganglionopathy progression.

neuroscience↗

bioRxiv2023

Comparative multi-omics analyses of cardiac mitochondrial stress in three mouse models of frataxin deficiency

Cardiomyopathy is often fatal in Friedreich Ataxia (FA). However, the FA heart maintains adequate function until disease end stage, suggesting that it can initially adapt to the loss of frataxin (FXN). Conditional knockout mouse models with no Fxn expression show transcriptional and metabolic profiles of cardiomyopathy and mitochondrial integrated stress response (ISRmt). However, ISRmt has not been investigated in models with disease-relevant, partial decrease of FXN. We characterized the heart transcriptomes and metabolomes of three mouse models of partial FXN loss, YG8-800, KIKO-700, and FxnG127V. Few metabolites were significantly changed in YG8-800 mice and did not provide a signature of cardiomyopathy or ISRmt. Instead, several metabolites were altered in FxnG127V and KIKO-700 hearts. Transcriptional changes were found in all models, but differentially expressed genes consistent with cardiomyopathy and ISRmt were only identified in FxnG127V hearts. However, these changes were surprisingly mild even at an advanced age (18-months), despite a severe decrease in FXN levels to 1% of WT. These findings indicate that the mouse heart has extremely low reliance on FXN, highlighting the difficulty in modeling genetically relevant FA cardiomyopathy. Summary statementThe mitochondrial integrated stress response in the heart of a Friedreich Ataxia mouse model is surprisingly mild, despite a severe decrease in frataxin levels below 1% of normal.

molecular biology↗

bioRxiv2022

Epidermal maintenance of Langerhans cells relies on autophagy-regulated lipid metabolism

Macroautophagy (often-named autophagy), a catabolic process involving autophagy-related (Atg) genes, prevents accumulation of harmful cytoplasmic components and mobilizes energy reserves in long-lived and self-renewing cells. Autophagy deficiency affects antigen presentation in conventional dendritic cells (DCs) without impacting their survival. However, previous studies did not address epidermal Langerhans cells (LCs). Here, we demonstrate that deletion of either Atg5 or Atg7 in LCs leads to their gradual depletion. ATG5-deficient LCs showed metabolic dysregulation and accumulated neutral lipids. Despite increased mitochondrial respiratory capacity, they were unable to process lipids, eventually leading them to ferroptosis. Finally, metabolically impaired LCs upregulated proinflammatory transcripts and showed decreased expression of neuronal interaction receptors. Altogether, autophagy represents a critical regulator of lipid storage and metabolism in LCs, allowing their maintenance in the epidermis.

immunology↗

bioRxiv2020

High levels of frataxin overexpression leads to mitochondrial and cardiac toxicity in mouse models

Friedreich ataxia (FA) is currently an incurable inherited mitochondrial disease caused by reduced levels of frataxin (FXN). Cardiac dysfunction is the main cause of premature death in FA. AAV-mediated gene therapy constitutes a promising approach for FA, as demonstrated in cardiac and neurological mouse models. While the minimal therapeutic level of FXN protein to be restored and biodistribution have recently been defined for the heart, it is unclear if FXN overexpression could be harmful. Indeed, depending on the vector delivery route and dose administrated, the resulting FXN protein level could reach very high levels in the heart, cerebellum, or in off-target organs such as the liver. The present study demonstrates safety of FXN cardiac overexpression up to 9-fold the normal endogenous level, but significant toxicity to the mitochondria and heart above 20-fold. We show gradual severity with increasing FXN overexpression, ranging from subclinical cardiotoxicity to left ventricle dysfunction. This appears to be driven by impairment of mitochondria respiratory chain, ultrastructure and homeostasis, which lead to myofilaments alteration, cell death and fibrosis. Overall, this study underlines the need, during the development of gene therapy approaches, to consider appropriately vector potency, long term safety and biomarkers to monitor such events.

bioengineering↗