Loss-of-function mutations in MICU1 cause a brain and muscle disorder linked to primary alterations in mitochondrial calcium signaling

Mitochondrial Ca 2+ uptake has key roles in cell life and death. Physiological Ca 2+ signaling regulates aerobic metabolism, whereas pathological Ca 2+ overload triggers cell death. Mitochondrial Ca 2+ uptake is mediated by the Ca 2+ uniporter complex in the inner mitochondrial membrane, which comprises MCU, a Ca 2+ -selective ion channel, and its regulator, MICU1. Here we report mutations of MICU1 in individuals with a disease phenotype characterized by proximal myopathy, learning difficulties and a progressive extrapyramidal movement disorder. In fibroblasts from subjects with MICU1 mutations, agonist-induced mitochondrial Ca 2+ uptake at low cytosolic Ca 2+ concentrations was increased, and cytosolic Ca 2+ signals were reduced. Although resting mitochondrial membrane potential was unchanged in MICU1-deficient cells, the mitochondrial network was severely fragmented. Whereas the pathophysiology of muscular dystrophy and the core myopathies involves abnormal mitochondrial Ca 2+ handling, the phenotype associated with MICU1 deficiency is caused by a primary defect in mitochondrial Ca 2+ signaling, demonstrating the crucial role of mitochondrial Ca 2+ uptake in humans. © 2014 Nature America, Inc