Calcium mishandling in absence of primary mitochondrial dysfunction drives cellular pathology in Wolfram Syndrome
Publication: Nature.com | Publication Date: March 16, 2020
Authors: Chiara La Morgia, Alessandra Maresca, Giulia Amore, Laura Ludovica Gramegna, Michele Carbonelli, Emanuela Scimonelli, Alberto Danese, Simone Patergnani, Leonardo Caporali, Francesca Tagliavini, Valentina Del Dotto, Mariantonietta Capristo, Federico Sadun, Piero Barboni, Giacomo Savini, Stefania Evangelisti, Claudio Bianchini, Maria Lucia Valentino, Rocco Liguori, Caterina Tonon, Carlotta Giorgi, Paolo Pinton, Raffaele Lodi & Valerio Carelli
Abstract
Wolfram syndrome (WS) is a recessive multisystem disorder defined by the association of diabetes mellitus and optic atrophy, reminiscent of mitochondrial diseases. The role played by mitochondria remains elusive, with contradictory results on the occurrence of mitochondrial dysfunction. We evaluated 13 recessive WS patients by deep clinical phenotyping, including optical coherence tomography (OCT), serum lactic acid at rest and after standardized exercise, brain Magnetic Resonance Imaging, and brain and muscle Magnetic Resonance Spectroscopy (MRS). Finally, we investigated mitochondrial bioenergetics, network morphology, and calcium handling in patient-derived fibroblasts. Our results do not support a primary mitochondrial dysfunction in WS patients, as suggested by MRS studies, OCT pattern of retinal nerve fiber layer loss, and, in fibroblasts, by mitochondrial bioenergetics and network morphology results. However, we clearly found calcium mishandling between endoplasmic reticulum (ER) and mitochondria, which, under specific metabolic conditions of increased energy requirements and in selected tissue or cell types, may turn into a secondary mitochondrial dysfunction. Critically, we showed that Wolframin (WFS1) protein is enriched at mitochondrial-associated ER membranes and that in patient-derived fibroblasts WFS1 protein is completely absent. These findings support a loss-of-function pathogenic mechanism for missense mutations in WFS1, ultimately leading to defective calcium influx within mitochondria.
Batjargal, K., Tajima, T., Jimbo, E.F. et al. Effect of 4-phenylbutyrate and valproate on dominant mutations of WFS1 gene in Wolfram syndrome. J Endocrinol Invest 43, 1317–1325 (2020). Retrieved February 16, 2024, from https://doi.org/10.1007/s40618-020-01228-2.