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Neurological disorders are linked to mitochondrial dysfunction and calcium overload. Mitochondrial calcium uptake is mediated by the mitochondrial calcium uniporter (mtCU), regulated by MICU1, which can be either homodimerized or heterodimerized with MICU2 or MICU3. Though MICU2 is scarce in the adult brain, MICU2 loss in patients leads to a neurodevelopmental disorder. We hypothesized that MICU2 is required for developmental calcium signaling and neuronal migration. MICU2 is present in the developing mouse brain but disappears by maturation, contrasting with other mtCU subunits that increase. MICU2 loss in mice does not affect cytoplasmic calcium but augments the mitochondrial matrix calcium rise in primary cortical neurons, leading to neuronal overmigration in the cortex and behavioral changes at 2 but not 12 months. Consistently, mitochondrial calcium uptake is not significantly affected in the adult animal cortex. MICU2-deficient patient fibroblasts copy the mitochondria-confined calcium alteration in developing neurons. Thus, MICU2 is important during neurodevelopment, likely by regulating the mtCU, and is eliminated by brain maturation.
Berezhnaya et al. (Fri,) studied this question.