Characterisation of infantile cardiomyopathy in Alström syndrome using ALMS1 knockout induced pluripotent stem cell derived cardiomyocyte model

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.