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Alström syndrome (AS) is an inherited rare ciliopathy characterised by multi-organ dysfunction and premature cardiovascular disease. This may manifest as an infantile-onset dilated cardiomyopathy with significant associated mortality. An adult-onset restrictive cardiomyopathy may also feature later in life. Loss of function pathogenic variants in ALMS1 have been identified in AS patients, leading to a lack of ALMS1 protein. The biological role of ALMS1 is unknown, particularly in a cardiovascular context. To understand the role of ALMS1 in infantile cardiomyopathy, the reduction of ALMS1 protein seen in AS patients was modelled using human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), in which ALMS1 was knocked out. MuscleMotion analysis and calcium optical mapping experiments suggest that ALMS1 knockout (KO) cells have increased contractility, with altered calcium extrusion and impaired calcium handling dynamics compared to wildtype (WT) counterparts. Seahorse metabolic assays showed ALMS1 knockout iPSC-CMs had increased glycolytic and mitochondrial respiration rates, with ALMS1 knockout cells portraying increased energetic demand and respiratory capacity than WT counterparts. Using senescence associated β-galactosidase (SA-β gal) staining assay, we identified increased senescence of ALMS1 knockout iPSC-CMs. Overall, this study provides insights into the molecular mechanisms in AS, particularly the role of ALMS1 in infantile cardiomyopathy in AS, using iPSC-CMs as a 'disease in a dish' model to provide insights into multiple aspects of this complex disease., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Alström syndrome (AS) is characterised by metabolic deficits, retinal dystrophy, sensorineural hearing loss, dilated cardiomyopathy and multi-organ fibrosis. Elucidating the function of the mutated gene, ALMS1, is critical for the development of specific treatments and may uncover pathways relevant to a range of other disorders including common forms of obesity and type 2 diabetes. Interest in ALMS1 is heightened by the recent discovery of its involvement in neonatal cardiomyocyte cell cycle arrest, a process with potential relevance to regenerative medicine. ALMS1 encodes a ~ 0.5 megadalton protein that localises to the base of centrioles. Some studies have suggested a role for this protein in maintaining centriole-nucleated sensory organelles termed primary cilia, and AS is now considered to belong to the growing class of human genetic disorders linked to ciliary dysfunction (ciliopathies). However, mechanistic details are lacking, and recent studies have implicated ALMS1 in several processes including endosomal trafficking, actin organisation, maintenance of centrosome cohesion and transcription. In line with a more complex picture, multiple isoforms of the protein likely exist and non-centrosomal sites of localisation have been reported. This review outlines the evidence for both ciliary and extra-ciliary functions of ALMS1.