Complex I is essential for embryonic stem cell proliferation through NADH-mediated redox signaling

Loss of mitochondrial respiratory Complex I via Ndufs1 knockout in mouse embryonic stem cells profoundly reduces proliferation rates while preserving pluripotent identity.

• Why it matters: The specific roles of respiratory complex components in regulating ESC self-renewal are unclear, despite known links between mitochondrial metabolism and ESC fate decisions.
• What they did: Using CRISPR/Cas9 to generate Ndufs1-knockout mouse ESCs, the study measured proliferation and cell-cycle dynamics by flow cytometry, mitochondrial physiology and redox state by multiple dyes/assays, and pluripotency by immunostaining, Western blotting, teratoma formation, and directed differentiation.
• The result: Ndufs1 deficiency induced mitochondrial reductive stress with decreased cellular NAD/NADH ratio and elevated ROS, and cytosolic NADH accumulation limited proliferation independently of energy depletion or excessive ROS, activating the integrated stress response and suppressing the NRF2/PGC-1/SOD2 antioxidant axis.