Mitochondrial Dysfunction and Calcium Dysregulation in Leigh Syndrome Induced Pluripotent Stem Cell Derived Neurons

Abstract

Leigh syndrome (LS) is the most frequent infantile mitochondrial disorder (MD) and is characterized by neurodegeneration and astrogliosis in the basal ganglia or the brain stem. At present, there is no cure or treatment for this disease, partly due to scarcity of LS models. Current models generally fail to recapitulate important traits of the disease. Therefore, there is an urgent need to develop new human in vitro models. Establishment of induced pluripotent stem cells (iPSCs) followed by differentiation into neurons is a powerful tool to obtain an in vitro model for LS. Here, we describe the generation and characterization of iPSCs, neural stem cells (NSCs) and iPSC-derived neurons harboring the mtDNA mutation m.13513G>A in heteroplasmy. We have performed mitochondrial characterization, analysis of electrophysiological properties and calcium imaging of LS neurons. Here, we show a clearly compromised oxidative phosphorylation (OXPHOS) function in LS patient neurons. This is also the first report of electrophysiological studies performed on iPSC-derived neurons harboring an mtDNA mutation, which revealed that, in spite of having identical electrical properties, diseased neurons manifested mitochondrial dysfunction together with a diminished calcium buffering capacity. This could lead to an overload of cytoplasmic calcium concentration and the consequent cell death observed in patients. Importantly, our results highlight the importance of calcium homeostasis in LS pathology.

Metabolism navigates neural cell fate in development, aging and neurodegeneration

“…This might lead to a general instability of neuronal cell identity and a block of maturation. Consequently, these neurons are locked in an immature state and thus more prone to programmed cell death, a feature that is exclusive for precursor cells and immature neurons ( Galera-Monge et al, 2020 ; Kole et al, 2013 ). Taken together, oxidative phosphorylation deficiencies are often compensated by residual mitochondrial function, but, in conditions with severe oxidative phosphorylation impairments, increased glycolytic activity hinders the development of mature neurons.…”

Dental Pulp-Derived Mesenchymal Stem Cells for Modeling Genetic Disorders

“…The third reason is the establishment of disease models [ 109 , 110 ]. Several iPSCs have been successfully established from patients with LS carrying mtDNA mutations and differentiated into muscles and neurons for analysis [ 111 , 112 ]. However, reprogramming to establish iPSCs may affect the nuclear genome and mtDNA stability and the patient-specific heteroplasmic state associated with uneven mitochondrial segregation during reprogramming [ 113 , 114 , 115 ].…”

Modelling Mitochondrial Disease in Human Pluripotent Stem Cells: What Have We Learned?

“…Mutations in more than 75 genes (both nDNA and mtDNA encoded) can result in Leigh syndrome [ 135 ]. Thus far, investigations have been reported for Leigh syndrome iPSC-derived neuronal cell types possessing mutations in: MT-ATP6 [ 98 , 136 ], MT-ND5 [ 102 ], NDUFS4 and SURF1 [ 137 ], and SCO2 [ 99 ].…”