m.3243A > G-Induced Mitochondrial Dysfunction Impairs Human Neuronal Development and Reduces Neuronal Network...

Area of Science:

• Neuroscience
• Cell Biology
• Genetics

Background:

• Mitochondrial diseases frequently cause neurological and psychiatric issues.
• Understanding how mitochondrial dysfunction impacts neural structure and function is limited by a lack of suitable in vitro models.
• The m.3243A > G variant in mitochondrial DNA is a common cause of MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes).

Purpose of the Study:

• To create and characterize an in vitro model of neuronal mitochondrial dysfunction using patient-derived cells.
• To investigate the effects of mitochondrial dysfunction on neuronal development, structure, and network activity.

Main Methods:

• Induced pluripotent stem cell (iPSC) technology was used to generate excitatory cortical neurons (iNeurons).
• Neurons were derived from patients with the m.3243A > G MELAS variant, creating an isogenic background with differing levels of mitochondrial heteroplasmy (normal vs. impaired function).
• Neuronal maturation, dendritic complexity, synapse formation, and network activity (via micro-electrode array) were assessed.

Main Results:

• Neurons with high mitochondrial heteroplasmy showed significant mitochondrial dysfunction.
• These neurons displayed delayed maturation, reduced dendritic complexity, and fewer excitatory synapses compared to controls.
• Network recordings revealed decreased overall activity and synchronous network bursting.

Conclusions:

• Mitochondrial dysfunction in neurons leads to impaired energy metabolism and compromised structural and functional integrity.
• These neuronal and network deficits are potential primary causes for the neuropsychiatric manifestations observed in mitochondrial diseases.
• Patient-derived iNeurons provide a valuable model for studying mitochondrial disease pathogenesis.