Dissecting the neuronal pathology of Leigh syndrome using patient-derived neurons and brain organoids

• Applicants: Dr. Sidney Cambridge; Professor Alessandro Prigione, Ph.D.
• Subject Area: Experimental Models for the Understanding of Nervous System Diseases ; Molecular and Cellular Neurology and Neuropathology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 551389629

Leigh syndrome (LS) is a fatal mitochondrial disease in children. It causes movement defects and intellectual disabilities, and the disease course rapidly deteriorates following episodes of metabolic stress. LS typically impairs dopaminergic neurons in the basal ganglia and midbrain regions in the central nervous system. No causative treatment is currently available, and the mechanisms underlying the neuronal pathology are not well understood. One gene frequently mutated in LS patients is SURF1, which encodes for a mitochondrial protein involved in energy metabolism. Animal models of SURF1 deficiencies do not recapitulate the patient defects, hindering the development of therapeutic interventions. We recently demonstrated that dopaminergic neurons and cortical brain organoids from engineered or patient-derived human pluripotent stem cells (iPSCs) carrying SURF1 mutations reproduce features seen in patients, including defective bioenergetics and neuronal dysfunctions. In particular, we identified an aberrant morphological branching pattern in SURF1-mutant neurons. We now propose to investigate in more detail the underlying mechanisms to determine possible links between impaired neuronal branching and cellular bioenergetics. We will employ human dopaminergic neurons in two-dimensional (2D) cultures and region-specific midbrain organoids (3D) as experimental models for LS. First, defects in neuronal branching and activities will be characterized and validated in midbrain organoids. Second, we will test the hypothesis that aberrant mitochondrial anchoring and trafficking may represent a link between defective bioenergetics and impaired neuronal morphogenesis. We will genetically interfere with these processes using a new transfection approach that we found to work effectively in neurons. Using this method, we will next conduct a short interfering (si)RNA knockdown screen based on the ‘druggable genome’ (around 800 genes) to identify potential genetic modifiers and their corresponding FDA-approved drugs that could promote the branching capacity of impaired LS neurons. Lastly, we will evaluate the effects of these modifiers on morphology and function of 2D dopaminergic neurons and 3D midbrain organoids. We will also analyze their role in response to various forms of metabolic stress to mimic the metabolic decompensation observed in patients. Our collaborative project has the potential to generate new mechanistic insights into the human neuronal pathology of LS, and might open the way to interventional strategies for this incurable pediatric disease with highly unmet medical needs.

• DFG Programme: Research Grants