Biology subjects

Argyriou, C.

Publications and source records attributed to Argyriou, C..

6 recordsLinked to original sources

bioRxiv2026

Distinct mitochondrial DNA single-nucleotide variant signatures in TOP3A-deficient cardiomyocytes

The human heart has a continuous and exceptionally high demand for energy, which is met primarily through mitochondrial oxidative phosphorylation. This dependence places the maintenance and integrity of mitochondrial DNA (mtDNA) for proper mitochondrial function at the center of cardiac health, as mtDNA instability has been shown to cause mitochondrial dysfunction, which can ultimately impair cardiac function leading to cardiomyopathy (CM) and heart failure. However, the contribution of mtDNA instability to cardiac disease remains poorly understood. A growing number of nuclear-encoded proteins have emerged as essential regulators of mtDNA maintenance, organization and segregation. DNA Topoisomerase 3 (TOP3A) is expressed as two isoforms: one is a nuclear-related isoform involved in nuclear genome maintenance while the other localizes to the mitochondria to preserve mtDNA integrity. Recently, individuals bearing biallelic loss-of-function variants in TOP3A manifested phenotypic traits, including CM, typical for mitochondrial dysfunction, supporting a potential mechanistic link between mitochondrial genome instability and TOP3A-related cardiac disease. Here, we investigated the effects of TOP3A deficiency on mtDNA maintenance and stability in the context of TOP3A-associated CM. We employed isogenic wild-type, TOP3A-knockout and BLM-knockout induced pluripotent stem cells (iPSCs) to generate cardiomyocytes (iPSC-CMs) and established a high-throughput, ultra-deep mtDNA sequencing strategy achieving approximately 500,000X coverage to characterize low-frequency mtDNA mutational patterns. Loss of TOP3A triggered an early burst of low-frequency de novo mtDNA single-nucleotide variants during cardiac differentiation, with a striking enrichment within the mitochondrial ribosomal RNA genes, accompanied by a progressive increase in the heteroplasmy of low-frequency mtDNA variants inherited from the common isogenic background. These unique mtDNA signatures were associated with defective mtDNA copy-number expansion and impaired mitochondrial respiration in mature iPSC-CMs. Together, our approach uncovered a previously uncharacterized consequence of TOP3A deficiency and established a link between impaired mtDNA maintenance and mitochondrial dysfunction in TOP3A-associated CM.

genetics↗

bioRxiv2026

Allele-specific correction of dominant Best vitelliform macular dystrophy in patient-derived retinal pigment epithelium

Autosomal dominant Best vitelliform macular dystrophy (BVMD) caused by variants in the BEST1 gene is characterized by dysfunction of the macular retinal pigment epithelium (RPE) and secondary degeneration of the photoreceptors. There are currently no approved treatments for BVMD, and owing to its dominant nature, there remains uncertainty regarding the utility of traditional gene augmentation. Here we evaluated whether a dominant pathogenic BEST1 allele can be corrected by base editing in differentiated RPE cells. We identified a patient with a likely pathogenic BEST1 c.851A>G (p. Tyr284Cys) variant that was amenable to cytidine base editing. After establishing patient-derived induced pluripotent stem cells (iPSCs), we corrected the pathogenic variant in the iPSCs to obtain corrected iPSCs with the same genetic background. Corrected iPSC-derived RPE exhibited normalized monolayer appearance, improved barrier integrity, reduced cell death, and restored RPE-specific transcriptome. We then used a dual adeno-associated virus (AAV) split-intein system to deliver a CRISPR-associated protein 9 cytidine base editor (SpCas9-CBE) to BEST1 c.851A>G mutant RPE monolayers and achieved editing of the pathogenic allele with a maximum efficiency of 13.42 {+/-} 3.64% (mean {+/-} SD). Together, these results demonstrate progress towards allele-specific base editing in a dominantly inherited retinal disorder.

neuroscience↗

bioRxiv2026

Clinically relevant AAV8-PEX1 gene therapy preserves retinal integrity and function long-term in a murine model of Zellweger spectrum disorder

Inherited retinal diseases (IRDs) are a heterogeneous group of genetic disorders that cause progressive vision loss. A subset of IRDs is associated with ubiquitously expressed genes involved in fundamental cellular processes, often resulting in multisystem disease. Among these is Zellweger spectrum disorder (ZSD), caused by pathogenic variants in PEX genes required for peroxisome biogenesis and function. There are no proven targeted disease-modifying treatments for ZSD, and it is unclear whether localized restoration of peroxisome function is sufficient to mitigate retinal degeneration. We previously demonstrated that HsPEX1 retinal gene augmentation therapy in a mouse model of mild ZSD homozygous for the murine equivalent (PEX1-p.[Gly844Asp]) of the most common deleterious allele in patients (PEX1-c.[2528G>A], PEX1-p.[Gly843Asp]), improved retinal electrophysiological response. Here, we present a comprehensive, dose-range evaluation of a re-designed, clinically relevant AAV8-delivered HsPEX1 subretinal gene therapy, employing expanded outcome measures. We observed a marked improvement in functional vision, retinal response, photoreceptor structure, retinal pigment epithelium integrity, subretinal inflammation, and peroxisomal metabolites, durable to the endpoint of 6 months post single subretinal injection. These studies provide preclinical proof-of-concept that localized retinal gene replacement can mitigate vision loss in peroxisome-mediated IRD.

genetics↗

bioRxiv2025

Longitudinal study of liver disease progression in the PEX1-Gly844Asp mouse model of mild Zellweger Spectrum Disorder

IntroductionZellweger spectrum disorder (ZSD) is an autosomal recessive disorder caused by mutations in any of 13 PEX genes encoding proteins required for peroxisome assembly and function. Chronic liver disease is one of the major clinical manifestations in patients and impacts quality of life and survival. However, the pathophysiology of liver disease is ZSD remains largely unknown, and current interventions are limited. To further study the liver disease mechanism, we use the PEX1-Gly844Asp (G844D) mouse model for mild ZSD, which was previously shown to develop hepatomegaly and cholestasis, similar to ZSD patients. MethodsThe natural history of hepatopathy was broadly characterized in PEX1-G844D mice and littermate controls from 1 to 18 months of age using liver histology, electron microscopy, cultured hepatocytes and blood. Metabolite and mechanism analysis included liver functions, respiratory chain dynamics, lipidomics, peroxisome metabolites, gene and protein expression assays. ResultsPEX1-G844D mice featured liver disease progression from hepatomegaly (1 month) to cluster cell death (4 months), hepatosteatosis (6 months), inflammation (8 months), fibrosis, and hepatic cancer (12 and 15 months). Hepatocyte proliferation and reduced glycogen was observed across all ages. Measurement of peroxisomal functions showed defective peroxisomal import and secondary mitochondrial defects in cultured hepatocytes. In blood and liver, plasmalogens were decreased, and C26:0 lyso-phosphatidylcholine and C27 bile acid intermediates were elevated. In liver, we observed accumulation of triglycerides and cholesterol, and reduced membrane phospholipids and sphingolipids. In contrast, in serum we observed reduced triglycerides, cholesterol and membrane lipids. Gene expression profiles confirmed by immunoblotting supported reduced hepatic de novo lipogenesis, increased hepatic lipid uptake and oxidation, PPAR activation, and modulated glucose and glycogen metabolism. Liver X receptor agonist (T0901317) applied to cultured hepatocytes enhanced hepatic lipogenesis and lipid secretion, but aggravated steatosis. ConclusionTaken together, these results suggested the following mechanisms of hepatopathy progression. We propose that global peroxisome dysfunction (1) causes PPAR activation, leading to chronic hyperplasia and partially contributing to disrupted hepatic lipid homeostasis with hepatosteatosis, and (2) underlies chronic hypoglycemia, causing hypoinsulinemia and contributing to reduced hepatic lipogenesis and systemic lipid deficiency. Growth restriction in the mouse model and in ZSD patients could be attributable to systemic lipid deficiency. Our mechanistic delineation of the pathophysiology provides other additional novel potential therapeutic targets to halt liver disease in ZSD.

pathology↗

bioRxiv2024

Geographic characterization of RPE structure and lipid changes in the PEX1-p.Gly844Asp mouse model for Zellweger spectrum disorder.

Peroxisome Biogenesis Disorders-Zellweger Spectrum (PBD-ZSD) are a heterogenous group of autosomal recessive disorders caused by defects in PEX genes whose proteins are required for peroxisome assembly and function. Peroxisomes are ubiquitous organelles that play a critical role in complex lipid metabolism. Dysfunctional peroxisomes in ZSD cause multisystem effects, with progressive retinal degeneration (RD) leading to childhood blindness being one of the most frequent clinical findings. Despite progress in understanding the role of peroxisomes in normal cellular functions, much remains unknown about how their deficiency causes RD, and there is no treatment. To study RD pathophysiology in this disease, we used the knock-in PEX1-p.GlyG844Asp (G844D) mouse model of milder ZSD, which represents the common human PEX1-p.Gly843Asp allele. We previously reported diminished retinal function, functional vision, and neural retina structural defects in this model. Beyond the neural retina, structural defects in retinal pigment epithelium (RPE) have been reported in ZSD patients and murine models with single peroxisome enzyme deficiency, suggesting that RPE degeneration may contribute to overall RD progression in this disease. Here, we investigate the RPE phenotype in our PEX1-G844D mouse model, observing morphological, inflammatory, and lipid changes at 1, 3, and 6 months of age. We report that RPE cell degeneration appears at 3 months of age and worsens with time, starts in the dorsal pole, and is accompanied by subretinal inflammatory cell infiltration. We match these events with lipid remodelling using imaging mass spectrometry which allowed regional analysis specific to the RPE cell layer. We identified 47 lipid alterations that precede structural changes, 10 of which are localized to the dorsal pole. 32 of these lipid alterations persist to 3 months, with remodelling of the lipid signature at the dorsal pole. 14 new alterations occur concurrent with histological changes. Changes in peroxisome-dependent lipids detected by liquid chromatography tandem mass spectrometry (reduced docosahexanoic acid and increased very long chain lysophosphatidylcholines) are exacerbated over time. This study represents the first characterization of RPE in any animal model of ZSD, and the first in situ lipid analysis in any peroxisome-deficient tissue. Our findings reveal candidate lipid drivers that could be targeted to alleviate RD progression in ZSD, as well as candidate biomarkers that could be used to evaluate retinopathy progression and response to therapy.

pathology↗

bioRxiv2020

Msp1/ATAD1 restores mitochondrial function in Zellweger Spectrum Disease

Peroxisomal Biogenesis Disorders (PBDs) are a class of inherited metabolic disorders with profound neurological and other phenotypes. The most severe PBDs are caused by mutations in peroxin genes, which result in nonfunctional peroxisomes typically through impaired protein import. In order to better understand the molecular causes of Zellweger Spectrum Disease (ZSD) -the most severe PBDs -, we investigated the fate of peroxisomal mRNAs and proteins in ZSD model systems. We found that loss of peroxisomal import has no effect on peroxin mRNA expression or translational efficiency. Instead, peroxin proteins--still produced at high levels-- aberrantly accumulate on the mitochondrial membrane, impairing respiration and ATP generation. Finally, we rescued mitochondrial function in fibroblasts derived from human patients with ZSD by overexpressing ATAD1, an AAA-ATPase that functions in mitochondrial quality control. These findings might provide a new focus of PBD therapies in supporting quality control pathways that protect mitochondrial function.

cell biology↗