https://www.um.edu.mt/library/oar/handle/123456789/402 2026-10-31T22:08:28Z https://www.um.edu.mt/library/oar/handle/123456789/150671 Title: Motor dysfunction phenotypes in a drosophila model validate DAO as an ALS gene Authors: Tabone, Sylvana; Cacciottolo, Rebecca; Cauchi, Ruben J. Abstract: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterised by progressive motor neuron (MN) loss. Although rare pathogenic variants in the D-amino acid oxidase (DAO) gene have been proposed to cause familial ALS, inconsistent findings across mammalian models have hindered functional validation. Here, we establish and characterise a Drosophila model of DAO loss-of-function by targeting its highly conserved orthologue, Daao1. Constitutive Daao1 knockdown caused early developmental lethality, while surviving adult escapers exhibited profound flight and climbing impairments. Contrary to expectations, Daao1 deficiency did not elevate D-serine levels in larval or adult brains, and simultaneous knockdown of serine racemase (Srr), the enzyme responsible for D-serine synthesis, failed to rescue locomotor phenotypes. Tissue-specific silencing revealed that Daao1 is essential within both MNs and muscles, but not glia, for maintaining motor performance. RNA-seq of Daao1-deficient flies uncovered widespread transcriptional dysregulation affecting metabolism, peptide transport, immune activation and developmental pathways, accompanied by alternative splicing changes in genes required for neuronal morphology and synaptic organisation. Consistent with these molecular alterations, neuromuscular junctions (NMJs) displayed reduced axonal branching and bouton numbers, indicating disrupted neuromuscular connectivity. Remarkably, ubiquitous expression of human DAO rescued lethality and motor defects, demonstrating functional conservation and supporting a role for DAO in maintaining neuromuscular health. Together, our findings reveal a previously unrecognised, D-serine-independent role for DAO in neuromuscular integrity and provide functional evidence connecting DAO dysfunction to ALS-relevant phenotypes. The DAO-ALS Drosophila model provides a powerful platform for mechanistic studies and for evaluating human DAO variants of uncertain significance in ALS. 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/150670 Title: Large-scale exome analyses reveal new rare variant contributions in amyotrophic lateral sclerosis Authors: Hop, Paul J.; Kooyman, Maarten; Kenna, Brendan J.; Zwamborn, Ramona A. J.; van Eijk, Kristel R.; Wang, Yan; van Dijk, Charlotte H.; Bekema, Erwin; van Rheenen, Wouter; Beele, Paul; van Vugt, Joke J. F. A.; Al Khleifat, Ahmad; Iacoangeli, Alfredo; Cooper-Knock, Johnathan; Smith, Bradley N.; Topp, Simon; van der Kooi, Anneke J.; Fominykh, Vera; Drory, Vivian; Lerner, Yossef; Shovman, Yehuda; Rowe, Dominic B.; Williams, Kelly L.; McLaughlin, Russell L.; Hurt, Jessica; Huang, Yunfeng; Chen, Chia-Yen; Tsai, Ellen; Runz, Heiko; Aronica, Eleonora; Groen, Ewout J. N.; van Es, Michael A.; Jeroen Pasterkamp, R.; Farhan, Sali M. K.; Garton, Fleur C.; McRae, Allan F.; McCombe, Pamela A.; Henderson, Robert D.; Fan, Dongsheng; Šlachtová, Lenka; Høyer, Helle; Nishimura, Agnes L.; Cauchi, Ruben J.; Brylev, Lev; Rogelj, Boris; Koritnik, Blaž; Zidar, Janez; Salas, Teresa; Mora Pardina, Jesus S.; Gotkine, Marc; Povedano, Monica; Corcia, Philippe; Vourc'h, Patrick; Couratier, Philippe; Weber, Markus; Kiernan, Matthew C.; Pamphlett, Roger; Blair, Ian P.; de Carvalho, Mamede; Başak, Nazli A.; Ingre, Caroline; Andersen, Peter M.; Zinman, Lorne; Rogaeva, Ekaterina; MacKenzie, Ian R.; Dupré, Nicolas; Rouleau, Guy A.; Traynor, Bryan J.; Ticozzi, Nicola; Chiò, Adriano; Silani, Vincenzo; Hardiman, Orla; Phatnani, Hemali; Harms, Matthew B.; Dalgard, Clifton L.; Glass, Jonathan D.; Landers, John E.; Van Damme, Philip; Morrison, Karen E.; Shaw, Pamela J.; van den Berg, Leonard H.; Kenna, Kevin P.; Veldink, Jan H. Abstract: Amyotrophic lateral sclerosis (ALS) is a heritable disorder where rare variants with low-to-moderate penetrance are thought to dominate genetic risk. To identify such rare variants, we harmonized and analyzed exome data from 22 cohorts, totaling 17,919 individuals with ALS and 200,703 controls across discovery and replication phases. Rare variant analyses identified several new risk genes, with replication confirming association of YKT6 and supporting HTR3C, GBGT1 and KNTC1. We also provide strong, independent validation for genes with limited previous evidence: ARPP21, DNAJC7 and CFAP410. Notably, in ARPP21, we identified a new high-effect variant (p.P747L) and confirmed that p.P563L is an ALS-associated variant leading to an aggressive disease course. Beyond new discoveries, our analyses largely recapitulated the known genetic architecture of ALS, identifying risk variants in over 20% of cases and supporting a cumulative oligogenic risk model. These findings highlight new translational targets and show that rare variant analyses capture substantially more genetic risk than common variant genome-wide association studies. 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/150669 Title: Epstein-Barr virus in multiple sclerosis pathogenesis : the path towards mechanistically faithful models Authors: Mizzi, Kathryn; Cauchi, Ruben J. Abstract: Multiple Sclerosis (MS) is a chronic, disabling autoimmune disease of the central nervous system (CNS). While its aetiology is multifactorial, compelling evidence now implicates Epstein-Barr virus (EBV) as a primary aetiological agent. This review summarises the extensive epidemiological and mechanistic data supporting a causal link between EBV infection and MS. Epidemiological studies demonstrate that EBV infection confers >30-fold increased risk for MS, with seroconversion preceding the onset of neuroaxonal damage. The leading proposed mechanism is molecular mimicry, where antibodies and T cells targeting the EBV nuclear antigen 1 (EBNA1) cross-react with CNS proteins, such as GlialCAM, initiating autoimmune-mediated demyelination. This process is modulated by synergistic interactions with genetic risk factors, and environmental factors like smoking and adolescent obesity. A critical evaluation of the experimental models used to investigate this connection is presented. In vitro systems using patient-derived cells have confirmed dysregulated immune responses to EBV antigens, while in vivo models ranging from murine experimental autoimmune encephalomyelitis (EAE) and humanised mice to non-human primate models with homologous γ-herpesviruses have been instrumental in demonstrating the role of EBV in breaking immune tolerance and driving neuroinflammation. Despite their utility, each model possesses limitations, underscoring the need for next-generation model systems that more accurately recapitulate the complex interplay between the virus, host genetics, and the CNS environment. Future research focused on refining these models is crucial for developing targeted EBV-based therapeutics, such as vaccines or antiviral agents, to prevent or treat MS. 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/150668 Title: ALS : a field in motion Authors: Cauchi, Ruben J.; Tosolini, Andrew P. Abstract: Amyotrophic lateral sclerosis (ALS) is a multifactorial neurodegenerative disorder driven by complex interactions among genetic, environmental, developmental, and resilience-related factors. The studies in this Scientific Reports Collection highlight major advances across diverse domains that collectively broaden our understanding of ALS pathogenesis. Genetic insights emphasise the need for functional validation, as shown by the non-pathogenic behaviour of the KIF5A P986L variant in Drosophila. Neuroimaging findings reveal hypothalamic atrophy in primary lateral sclerosis, underscoring widespread extra-motor involvement. Epidemiological analyses propose that early-life exposures may form the initial steps in a multistage pathway to ALS, while geographic correlations between ALS and multiple sclerosis suggest shared environmental determinants. Experimental model innovations demonstrate selective muscle preservation in SOD1-G93A mice and introduce electrical impedance myography as a sensitive detection method in zebrafish. Mechanistic work shows that stress influences ALS through PI3K/Akt and focal adhesion pathways, linking environment to cellular vulnerability. Finally, cognitive and brain reserve emerge as important modifiers of disease expression and progression. Together, these studies illustrate ALS as a multisystem, lifespan-spanning disorder shaped by both vulnerability and resilience. Their integration offers a forward-looking framework for advancing biomarker discovery, mechanistic research, and therapeutic development in ALS. 2025-01-01T00:00:00Z