Disease-specific phenotypes in iPSC-derived neural stem cells with POLG mutations

Area of Science:

• Genetics
• Neuroscience
• Cell Biology

Background:

• Mutations in the POLG gene impair mitochondrial DNA (mtDNA) replication, leading to severe diseases with neurological symptoms.
• Studying neuronal defects in these POLG-related disorders is challenging due to limited access to human brain tissue.

Purpose of the Study:

• To establish a human stem cell model that recapitulates the molecular and biochemical defects in neurons caused by POLG mutations.
• To investigate the mechanisms underlying neuronal dysfunction in POLG-related diseases.

Main Methods:

• Generation of induced pluripotent stem cells (iPSCs) from patient cells with POLG mutations.
• Differentiation of iPSCs into neural stem cells and dopaminergic neurons.
• Analysis of mtDNA content, mitochondrial complex I activity, reactive oxygen species (ROS) production, cellular senescence, NAD+ metabolism, and mitophagy.

Main Results:

• Neural precursors derived from POLG-mutant iPSCs exhibited molecular and biochemical phenotypes mirroring patient brain tissue.
• Neurons generated from these stem cells showed mtDNA loss, reduced complex I activity, increased ROS, and cellular senescence.
• Dysfunctional mitochondrial NAD+ metabolism and activated mitophagy via the BNIP3 pathway were observed in cells with compound heterozygous POLG mutations.

Conclusions:

• This study presents the first human stem cell model capable of replicating neuronal defects associated with POLG mutations.
• The findings provide crucial insights into how mitochondrial dysfunction and mtDNA alterations impact neuronal fate and disease progression.