Biology subjects

Lopez de Munain, A.

Publications and source records attributed to Lopez de Munain, A..

15 recordsLinked to original sources

bioRxiv2026

Loss of TDP-43 drives premature aging and impairs skeletal muscle stem cell pool restoration

TAR DNA-binding protein 43 (TDP-43) dysfunction is a hallmark of amyotrophic lateral sclerosis (ALS) and related disorders, yet its role in skeletal muscle stem cells, the satellite cells (SC), remains incompletely understood. Here, we investigated ALS-associated gain- and loss-of-function TDP-43 mutations together with inducible SC-specific TDP-43 deletion. While TDP-43Q331K and heterozygous TDP-43F210I mice displayed normal muscle homeostasis, SC abundance, and regenerative capacity, complete TDP-43 loss caused a marked reduction of the SC pool, particularly in females, and shifted SCs from a CD34high stem-like state toward a CD34low primed population. TDP-43-deficient SCs failed to clonally expand, proliferate, and differentiate, resulting in severe regenerative failure following muscle injury. Notably, the SC pool failed to recover after injury and was nearly depleted 30 days post-injury, accompanied by muscle loss, fibrosis and fat infiltration. Transcriptomic analyses revealed activation of stress and aging-associated programs in uninjured TDP-43-deficient SCs, indicating the premature acquisition of an aging-like state. Consistently, chronological aging further exacerbated SC depletion, establishing TDP-43 as a critical regulator of SC stemness, regeneration, and resistance to age-related decline.

cell biology↗

bioRxiv2026

Muscle spatial lipidomics identifies early ALS signatures in presymptomatic SOD1G93A mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease whose diagnosis often remains delayed. Skeletal muscle is increasingly recognized as an early contributor to ALS pathology. Using lipid imaging mass spectrometry (LIMS) in Tibialis anterior muscle from hSOD1G93A mice across disease stages, we identified fiber-type-specific and sex-dependent lipid remodeling. Lipid alterations were detected at the presymptomatic stage, preceding motor neuron loss and clinical symptoms. LIMS distinguished fast-twitch oxidative-glycolytic (type IIA) and glycolytic (type IIB/IIX) fibers and revealed their differential vulnerability to disease. Presymptomatic mutant muscles showed loss of physiological lipid signatures alongside disease-specific lipid changes. Although lipid profiles differed between sexes, ALS-associated alterations enabled accurate discrimination of mutant mice before symptom onset. Importantly, similar disease-related lipid changes were detected in serum, enabling accurate classification of presymptomatic animals. These findings establish lipid remodeling as an early ALS event and highlight novel biomarkers with potential for diagnosis and disease monitoring.

neuroscience↗

bioRxiv2026

Comprehensive characterization of skeletal muscle remodeling in hSOD1G93A mice reveals limited functional impact of systemic FOXO1 inhibition

BackgroundAmyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive motor neuron (MN) loss, muscle atrophy and paralysis. Although traditionally considered a MN-specific disease, accumulating evidence supports a crucial contribution of skeletal muscle pathology to disease onset and progression. Except for specific mutations, to date there is no effective treatment for ALS. FOXO transcription factors regulate programs of atrophy, metabolism and stress response in skeletal muscle, and their inhibition has shown beneficial effects in cellular and Drosophila models of ALS. MethodsIn this study, we investigated whether pharmacological FOXO inhibition (iFOXO) could modify disease progression and muscle pathology in female hSOD1G93A mice. Mice received daily oral administration of iFOXO starting at presymptomatic (P50; n=5 per group) or symptomatic (P90; n=9 mice per group) stages until end-stage. Body weight was monitored longitudinally, and motor performance was evaluated using grip strength and hanging-wire tests. Tibialis anterior and soleus muscles, representing fast- and slow-twitch muscles respectively, were analyzed by histology and immunofluorescence to assess fiber atrophy, fibrosis, lipid accumulation, satellite cell pool and fiber type composition. Quadriceps muscles (n=3 per group) were used for RNA-seq analysis. ResultsWhile histological analyses revealed severe fiber atrophy and increased fibrosis in hSOD1G93A mice, satellite cell numbers were preserved or mildly increased in a muscle and treatment onset dependent manner. iFOXO treatment did not improve motor performance, survival or attenuate muscle atrophy. Transcriptomic profiling indicated that genotype was the predominant driver of gene expression changes, while iFOXO produced only subtle, treatment onset dependent effects on pathways related to oxidative stress responses, mitochondrial function and adaptive metabolism. ConclusionOverall, FOXO inhibition alone showed limited therapeutic benefit in the hSOD1G93A ALS mouse model. These findings highlight the dominant influence of ALS driven molecular alterations over pharmacological modulation and emphasize the need for combinatorial therapeutic strategies targeting multiple disease mechanisms, including those preserving nerve health.

neuroscience↗

bioRxiv2026

Targeted 3'-end RNA sequencing uncovers cryptic polyadenylation in Huntington's disease linked to somatic instability and CAG repeat purity

Huntingtons disease (HD) is a progressive neurodegenerative disorder caused by expanded CAG repeats in the first exon of the HTT gene, which encodes for huntingtin (HTT) protein. Full-penetrance is established at 40 repeats, but beyond, somatic repeat instability in the brain and CAG repeat purity modulate disease onset and severity. Previous studies have described that expanded repeats induce the incomplete splicing of HTT intron 1 to express the most pathogenic HTT isoform, known as HTT1a. Yet, the lack of a robust and sensitive method to evaluate HTT RNA-misprocessing has limited our understanding of HTT1a expression in HD pathophysiology. Here we describe a targeted RNA sequencing approach, known as 3-end targeted RNA sequencing or 3TRS, to simultaneously quantify multiple HTT transcripts generated by canonical and cryptic polyadenylation in several HD models. We show that activation of HTT cryptic polyadenylation is highly selective and requires long and uninterrupted CAG repeat expansions. In HD knock-in mice and human postmortem brain, cryptic HTT expression strongly correlates with brain-specific somatic repeat instability, supporting a model where ultralong and unstable CAG repeats drive toxicity by activating HTT RNA-misprocessing. Overall, 3TRS provides a robust framework to investigate HTT1a biogenesis and expression and to evaluate HTT-lowering therapeutic strategies. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/697463v2_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@168d8e1org.highwire.dtl.DTLVardef@76ba3forg.highwire.dtl.DTLVardef@bdaf93org.highwire.dtl.DTLVardef@151e581_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2025

A New Approach to Modeling LGMDR1: Pyrvinium-Treated capn3b crispant Zebrafish

The lack of an accurate animal model for LGMDR1 is a major obstacle to therapeutic development. While murine models do not replicate the human gene expression profile, zebrafish offers a promising alternative. We generated a capn3b mutant zebrafish, which showed minimal phenotypic changes. However, when this model was treated with pyrvinium, a Wnt signaling inhibitor, its gene expression patterns mimic those observed in LGMDR1 patients, reinforcing the role of the Wnt pathway in LGMDR1 pathology. This pharmacologically enhanced model, despite lacking a clear phenotype in young larvae, could serve as a valuable tool for identifying potential therapeutic targets upon further investigation and validation.

molecular biology↗

bioRxiv2025

Assessment of the pharmacological and safety profile of the small molecule MP-004 after topical eye drops administration

MP-004 is a novel small molecule under development as a non-invasive therapeutic for inherited retinal dystrophies (IRDs), including retinitis pigmentosa. Here, we evaluated its ocular concentration and safety profile following topical administration in three animal species --mouse, rabbit, and pig--. MP-004 formulation with 0.3% hyaluronic acid significantly enhanced retinal concentration in mice compared to non-formulated compound (6.67 vs 1.27 {micro}g/g at 4 h). MP-004 reached therapeutically relevant retinal concentrations in all species tested, with minimal systemic exposure: in mice, levels detected in serum were lower than 5 ng/mL while in rabbits, the compound was undetectable in blood and peripheral tissues 12 h post-dose. Seven-day repeated-dose toxicity studies in mice and rabbits showed no systemic or ocular toxicity. In rabbits, only transient ocular redness was observed post-administration, with no evidence of corneal damage or systemic adverse effects. Hematological and biochemical parameters in both species remained within normal limits. Importantly, retinal and optic nerve concentrations remained detectable in rabbits 7 days after final dosing, while the compound was eliminated systemically, supporting prolonged target tissue retention. These findings demonstrate that MP-004 is well tolerated and achieves effective retinal concentrations via topical delivery, overcoming a major barrier in retinal drug development. The favorable pharmacokinetic and safety profile across species, including anatomically relevant models, supports MP-004s advancement toward regulatory preclinical studies and clinical translation as a non-invasive therapy for IRDs.

pharmacology and toxicology↗

bioRxiv2025

Computational Analysis of ELOVL6 Structure and Inhibition for Rational Drug Design

ELOVL6 is a key enzyme in long-chain fatty acid elongation, catalyzing the conversion of C16 fatty acids into C18 fatty acids. While its role in lipid metabolism is well established, recent studies have linked ELOVL6 to metabolic and neurodegenerative diseases, making it an attractive therapeutic target. However, the absence of a resolved crystal structure and limited mechanistic understanding of its inhibition pose significant challenges for drug discovery. In this study, we employ a multi-tiered computational approach, including structure prediction, molecular dynamics (MD) simulations, and free energy calculations, to investigate the structural basis of ELOVL6 function and inhibition. We identify the most thermodynamically favorable substrate binding pathway and characterize key conformational changes associated with ligand binding. By analyzing potential inhibitor binding pockets, we determine that known inhibitors preferentially target the active site, and we validate their binding affinities against experimental data. Additionally, by comparing ELOVL6 with homologous elongases, we pinpoint potentially key amino acid residues responsible for selectivity, providing insights that could guide structure-based drug design. Our findings establish a mechanistic framework for rational inhibitor development, offering a foundation for future efforts in optimizing ELOVL6-targeting therapeutics.

bioinformatics↗

bioRxiv2025

Enhanced muscle uptake of chemically optimized miR-23b antisense oligonucleotides as lead compounds for Myotonic Dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a multisystemic disorder caused by CTG repeat expansions in DMPK. Mutant transcripts containing expanded CUG repeats form ribonuclear foci that sequester muscleblind-like splicing regulator (MBNL) proteins, key regulators of RNA splicing and metabolism. This functional depletion leads to widespread mis-splicing and persistence of fetal transcript profiles, which underlie muscle weakness, myotonia, and muscle atrophy. In addition, miR-23b is upregulated in DM1 muscle and further represses MBNL1 translation, amplifying molecular defects. We developed chemically optimized miRNA-targeting antisense oligonucleotides (antimiRs) to inhibit miR-23b and restore functional MBNL1 levels. Using a multi-step screening process, we evaluated antimiRs with varying sequences, lengths, chemical modifications, and lipid conjugations. A key optimization was a 3-oleic acid conjugation combined with specific chemical modifications, which enhanced muscle uptake and efficacy. Lead candidates showed strong activity in preclinical models (HSALR and DMSXL mice, and human myoblasts), increasing MBNL1 levels, correcting mis-splicing, improving muscle strength, and reducing myotonia. They also exhibited efficient biodistribution to skeletal muscle, a critical DM1-affected tissue. In vitro toxicology indicated a favorable safety profile with minimal immune or renal toxicity. The antimiR mechanism was conserved in rat and pig fibroblasts. Overall, two lead antimiRs emerged as promising therapeutic candidates for DM1, with improved pharmacokinetics, tissue targeting, and safety, supporting the potential of microRNA-based approaches to correct key molecular defects in this disorder.

genetics↗

bioRxiv2025

Characterisation of DMPK and MBNL1 expression in cell models of Myotonic Dystrophy: A platform for drug screening

Myotonic dystrophy type I (DM1) is caused by CTG repeat expansions in the DMPK gene leading to mRNA toxicity and sequestration of the splicing regulator MBNL1, affecting many tissues. We have developed an in vitro screening platform based on ddPCR and in-cell western to quantify these mRNAs and proteins and characterised more than 20 cell models to define DM1 biomarkers that could be useful for drug screening. DMPK protein levels were reduced in DM1-immortalised myoblasts and myotubes, but not in fibroblasts, while MBNL1 protein was consistently lower in all DM1 myogenic cultures, whether primary or immortalised. Myogenic differentiation of cultures led to an increase in DMPK mRNA expression, which was translated into increased MBNL1 sequestration in foci. We further corroborated the platforms ability to assess therapeutic outcomes, evaluating the effect of a DMPK gapmer ASO and one siRNA: while the gapmer increased MBNL1 protein levels, the siRNA had no significant effect on MBNL1 release. Our platform and the in-depth characterisation of some of the most used models would be of use to the DM1 research community. Significance statementMyotonic dystrophy type I (DM1) is a multisystemic disease with a complex pathogenesis and multiple outcome measures for drug assessment in vitro. In the last years, the increasing number of new potential therapies targeting DM1 in clinical trials has increased the need for robust and rapid evaluation of preclinical candidates, as well as in-depth knowledge of the cell models used. Here, we present a new cell-based platform that enables robust quantification of DMPK and MBNL1 in cell culture for cell model characterisation and drug screening. Indeed, we highlight the differences observed in DMPK and MBNL1 protein quantification in primary fibroblasts and myotubes, immortalised fibroblasts, myoblasts and myotubes. We then, we performed a proof-of-concept drug evaluation of potential therapeutic strategies targeting DMPK, showing the most suitable for targeting the DMPK expanded transcript.

cell biology↗

bioRxiv2024

Topical administration of novel FKBP12 ligand MP-004 improves retinal function and structure in retinitis pigmentosa models.

PurposeThis study evaluates the therapeutic potential of MP-004, a novel FKBP12 ligand, in the treatment of inherited retinal dystrophies (IRDs). MP-004 targets FKBP12/RyR interaction, which is disrupted in several neurological disorders with underlying oxidative stress. MethodsThe toxicity and efficacy of MP-004 were examined in vitro in 661W cells. Efficacy was evaluated in phototoxic and H2O2-induced damage using impedance assays, calcium igaing and in situ PLA. In vivo, MP-004 efficacy was evaluated in the rd10 mouse model of retinitis pigmenetosa (RP) by topical ocular instillation. Retinal function was assessed by electroretinography (ERG), visual acuity was measured using a water maze test, and retinal structure was analyzed morphometrically. ResultsMP-004 exhibited low toxicity (LD50: 1.22 mM) and effectively protected 661W cells from phototoxicity (EC50: 30.6 nM). Under oxidative stress conditions, MP-004 preserved FKBP12.6/RyR2 interaction, partially restored endoplasmic reticulum calcium stores and prevented cell death. In vivo, MP-004 significantly preserved retinal function in rd10 mice, with ERG wave amplitude increases of up to 50% in scotopic and 71% in photopic conditions, corresponding to rod and cone functions, respectively. Additionally, MP-004 improved visual acuity for low spatial frequency patterns, and preserved retinal structure with a 23% increase in outer nuclear layer thickness, and preservation in the number of rods and cones and their segment length. ConclusionsMP-004 shows promise as a therapeutic agent for RP, preserving retinal structure and function, likely through modulation of FKBP12.6/RyR2 interaction. Further studies are needed to explore its pharmacokinetics and efficacy in other IRD models.

neuroscience↗

bioRxiv2024

Energy scarcity and impaired mitochondrial translation induce perinuclear stress granule clustering

Many proteins linked to amyotrophic lateral sclerosis and fronto-temporal dementia (ALS-FTD) change their cellular location and coalesce in cytoplasmic inclusion bodies in the disease state; yet the factors that govern protein relocation and organization remain unclear. Here, we show that inhibition of glycolysis and mitochondrial protein synthesis causes many proteins involved in ALS-FTD to change location, and form a novel structure comprising a ring of stress granules encircling the aggresome, a focal microtubule-based structure beside the nucleus. A perinuclear ring of stress granules also forms in activated microglia of mice exposed to the glycolytic inhibitor, 2-Deoxy-D-glucose. We propose that the new arrangement increases the risk of the stress granules merging and converting from the liquid phase to the insoluble inclusion characteristic of ALS-FTD. Thus, our findings suggest that that compromised nutrient and energy metabolism can precipitate a molecular cascade that ultimately leads to the pathological hallmark of ALS-FTD the perinuclear inclusion body. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/578399v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@b32d48org.highwire.dtl.DTLVardef@161f848org.highwire.dtl.DTLVardef@f35c66org.highwire.dtl.DTLVardef@1375508_HPS_FORMAT_FIGEXP M_FIG C_FIG Inhibition of glycolysis and mitochondrial protein synthesis induces translocation of a swathe of ALS-FTD related proteins in primary human fibroblasts. The relocated proteins form concentric cytoplasmic rings (CCR) comprising stress granules, the Golgi and the aggresome, beside the nucleus. A perinuclear ring of stress granules forms in the mouse brain following intermittent nutrient restriction, with the glucose analog 2DG. The CCR is potentially a key intermediate step in the formation of pathological inclusions and so perturbed nutrient and energy metabolism encompassing impaired mitochondrial translation could precipitate the ALS-FTD disease cascade.

cell biology↗

bioRxiv2024

Lipid Dysregulation Unveil the Intricate Interplay of Lysosomal and Mitochondrial Changes in Frontotemporal Dementia with GRN Haploinsufficiency

This study investigates the cellular pathology resulting from haploinsufficiency of progranulin (PGRN) in frontotemporal dementia (FTD) associated with granulin (GRN) mutations. Utilizing fibroblasts from FTD patients carrying a distinctive GRN mutation (c.709-1G>A), we observed lysosomal and lipofuscin accumulation, impaired lysosomal function, compromised autophagic flux, and mitochondrial abnormalities. Notably, recombinant human progranulin (rhPGRN) treatment restored lysosomal acidification, mitigated mitochondrial defects, and demonstrated beneficial effects. FTD-GRN fibroblasts exhibited abnormal lipid metabolism with increased lipid droplet formation, influenced by GRN haploinsufficiency and modulated by rhPGRN. Under nutrient-rich conditions, lipid droplet dynamics were shaped by autophagy and mitochondrial processes, potentially due to impaired fatty acid oxidation. These findings highlight a direct association between GRN deficiency and altered lysosomal-mitochondrial interactions, influencing lipid metabolism and contributing to FTD pathogenesis. The documented lysosomal dysfunction, impaired autophagy, mitochondrial anomalies, and altered lipid metabolism collectively suggest a complex interplay of cellular processes in the development of FTD-GRN.

neuroscience↗

bioRxiv2024

Novel FKBP12 ligand promotes functional improvement in SOD1-G93A ALS mice

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease with limited treatment options. ALS pathogenesis involves intricate processes within motor neurons (MNs), characterized by dysregulated Ca2+ influx and buffering in early ALS-affected MNs. This study proposes the modulation of ryanodine receptors (RyRs), key mediators of intracellular Ca2+, as a therapeutic target. A novel class of novel FKBP12 ligands that show activity as cytosolic calcium modulators through stabilizing RyR channel activity, were tested in the SOD1G93A mouse model of ALS. Different outcomes were used to assess treatment efficacy including electrophysiology, histopathology, neuromuscular function, and survival. Among the novel FKBP12 ligands, MP-010 was chosen for its central nervous system availability. Chronic administration of MP-010 to SOD1G93A mice produced a dose-dependent preservation of motor nerve conduction, with the 61 mg/kg dose significantly delaying the onset of motor impairment. This was accompanied by improved motor coordination, increased innervated endplates, and significant preservation of MNs in the spinal cord of treated mice. Notably, MP-010 treatment significantly extended lifespan by an average of 10 days compared to vehicle. In conclusion, FKBP12 ligands, particularly MP-010, exhibit promising neuroprotective effects in ALS, highlighting their potential as novel therapeutic agents. Further investigations into the molecular mechanisms and clinical translatability of these compounds are needed for their application in ALS treatment.

neuroscience↗

bioRxiv2021

A novel Alex3/Gαq protein complex regulating mitochondrial dynamics, dendritic complexity, and neuronal survival

In neurons, mitochondrial dynamics and trafficking are essential to provide the energy required for neurotransmission and neuronal activity. Recent studies point to GPCR and G proteins as important regulators of mitochondrial dynamics and energy metabolism. Here we show that activation of Gq negatively regulates mitochondrial dynamics and trafficking in neurons. Gq interacts with the mitochondrial trafficking protein Alex3. By generating a CNS-specific armcx3 knock-out mouse line, we demonstrate that Alex3 is required for Gq effects on mitochondrial dynamics and trafficking, and dendritic growth. Armcx3-deficient mice present decreased OXPHOS complex and ER stress response protein levels, which correlate with increased neuronal death, motor neuron and neuromuscular synaptic loss, and severe motor alterations. Finally, we show that Alex3 disassembles from the Miro1/Gq complex upon calcium rise. These data uncover a novel Alex3/Gq complex that regulates neuronal mitochondrial dynamics and neuronal death and allows the control of mitochondrial functions by GPCRs.

cell biology↗

bioRxiv2020

Transcriptional Signatures of Synaptic Vesicle Genes Define Myotonic Dystrophy Type I Neurodegeneration

Despite significant research, the biological mechanisms underlying the brain degeneration in Myotonic Dystrophy Type I (DM1) remain largely unknown. Here we have assessed brain degeneration by measuring the volume loss (VL) and cognitive deficits (CD) in two cohorts of DM1 patients, and associating them to the large-scale brain transcriptome maps provided by the Allen Human Brain Atlas (AHBA). From a list of preselected hypothesis-driven genes, three of them appear to play a major role in degeneration: dystrophin (DMD), alpha-synuclein (SNCA) and the microtubule-associated protein tau (MAPT). Moreover, a purely data-driven strategy identified gene clusters enriched for key biological processes in the central nervous system, such as synaptic vesicle recycling, localization, endocytosis and exocytosis, and the serotonin and dopamine neurotransmitter pathways. Therefore, by combining large-scale transcriptome interactions with brain imaging and cognitive function, we provide a new more comprehensive understanding of DM1 that might help define future therapeutic strategies and research into this condition.

neuroscience↗