Alpers' syndrome is an early-onset neurodegenerative disorder usually caused by biallelic pathogenic variants in the gene encoding the catalytic subunit of polymerase-gamma (POLG), which is essential for mitochondrial DNA (mtDNA) replication. The disease is progressive, incurable, and inevitably it leads to death from drug-resistant status epilepticus. The neurological features of Alpers' syndrome are intractable epilepsy and developmental regression, with no effective treatment; the underlying mechanisms are still elusive, partially due to lack of good experimental models. Here, we generated the patient derived induced pluripotent stem cells (iPSCs) from one Alpers' patient carrying the compound heterozygous mutations of A467T (c.1399G>A) and P589L (c.1766C>T), and further differentiated them into cortical organoids and neural stem cells (NSCs) for mechanistic studies of neural dysfunction in Alpers' syndrome. Patient cortical organoids exhibited a phenotype that faithfully replicated the molecular changes found in patient postmortem brain tissue, as evidenced by cortical neuronal loss and depletion of mtDNA and complex I (CI). Patient NSCs showed mitochondrial dysfunction leading to ROS overproduction and downregulation of the NADH pathway. More importantly, the NAD+ precursor nicotinamide riboside (NR) significantly ameliorated mitochondrial defects in patient brain organoids. Our findings demonstrate that the iPSC model and brain organoids are good in vitro models of Alpers' disease; this first-in-its-kind stem cell platform for Alpers' syndrome enables therapeutic exploration and has identified NR as a viable drug candidate for Alpers' disease and, potentially, other mitochondrial diseases with similar causes.

Centre for International Health University of Bergen Bergen Norway

Department of Clinical Medicine University of Bergen Bergen Norway

Department of Clinical Molecular Biology Akershus University Hospital University of Oslo Oslo Norway

Department of Head and Neck Cancer Surgery West China Hospital of Stomatology Sichuan University Chengdu China

Department of Molecular Medicine Institute of Basic Medical Sciences University of Oslo 0317 Oslo Norway

Department of Neurology Beijing Tongren Hospital Capital Medical University Beijing China

Department of Neurology Haukeland University Hospital Bergen Norway

Department of Paediatrics and Inherited Metabolic Disorders 1st Faculty of Medicine Charles University Prague Czech Republic

Department of Pediatric Research Oslo University Hospital Oslo Norway

Institute of Immunology Oslo University Hospital Oslo Norway

KG Jebsen Center for Parkinson's disease University of Bergen Bergen Norway

National Advisory Unit for Congenital Metabolic Diseases Oslo University Hospital Oslo Norway

Neuro SysMed Center of Excellence for Clinical Research in Neurological Diseases Haukeland University Hospital Bergen Norway

Norwegian Center for Stem Cell Research University of Oslo 0317 Oslo Norway

State Key Laboratory of Oral Diseases National Clinical Research Center for Oral Diseases West China School of Stomatology Sichuan University Chengdu China

The Norwegian Centre on Healthy Ageing Oslo Norway

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