Mitochondrial respiratory dysfunction caused by a heteroplasmic mitochondrial DNA mutation blocks cellular...

Area of Science:

• Cellular and Molecular Biology
• Genetics and Genomics
• Mitochondrial Biology

Background:

• Mitochondrial dysfunction arises from pathogenic mutations in mitochondrial tRNA genes, manifesting only above specific mutant mitochondrial DNA (mtDNA) proportions.
• The precise mutant mtDNA levels impacting cellular lineage determination remain largely uncharacterized.
• Mitochondrial respiratory dysfunction is a key consequence of certain mtDNA mutations, such as the m.3243A>G heteroplasmy in the MT-TL1 gene.

Purpose of the Study:

• To investigate the impact of mitochondrial respiratory dysfunction, driven by m.3243A>G heteroplasmy, on cellular reprogramming and induced pluripotent stem cell (iPSC) generation.
• To determine the specific proportions of mutant mtDNA that affect cellular reprogramming processes.

Main Methods:

• Generation of induced pluripotent stem cells (iPSCs) from cells harboring varying proportions of the m.3243A>G mutation in the MT-TL1 gene.
• Assessment of mitochondrial respiratory function in relation to mutant mtDNA heteroplasmy levels.
• Evaluation of the pluripotent state of established iPSCs, including those with high mutant mtDNA loads.

Main Results:

• Induced pluripotent stem cell (iPSC) generation was significantly inhibited only at high mutant mtDNA proportions (≥ 90% m.3243A>G).
• The degree of induced mitochondrial respiratory dysfunction correlated strongly with these high mutant mtDNA proportions.
• All successfully generated iPSCs, even those with nearly 100% m.3243A>G heteroplasmy, exhibited an embryonic stem cell-like pluripotent state.

Conclusions:

• Loss of mitochondrial physiological integrity due to mutant mtDNA acts as a barrier to cellular rejuvenation during reprogramming.
• The maintenance of the pluripotent state in iPSCs is not compromised by high levels of mutant mtDNA.
• These findings highlight a dissociation between the efficiency of reprogramming and the stability of pluripotency in the context of mitochondrial dysfunction.