Cuproptosis causes meiotic metaphase I arrest by disrupting mitochondrial functions in oocytes

Abstract Proper oocyte maturation is critical for female fertility, yet whether cuproptosis, a recently identified copper-dependent cell death pathway, affects meiotic maturation remains unknown. Here, we show that Cu(II)-elesclomol (ELC-Cu(II)) treatment induces dose-dependent metaphase I arrest of mouse oocytes. This arrest results from spindle assembly checkpoint activation caused by defective spindle organization and impaired kinetochore-microtubule attachments. We demonstrate that ELC-Cu(II) triggers changes in canonical cuproptosis markers, including intracellular copper accumulation, FDX1 downregulation, and protein aggregation. Meanwhile, treated oocytes exhibit mitochondrial dysfunction characterized by reduced membrane potential and decreased ATP levels. Integrated transcriptomic and proteomic profiling reveals a predominantly post-transcriptional response, with 223 differentially expressed proteins, while transcriptomic profiles show minimal changes. Pathway analysis identifies dysregulation of lipoic acid metabolism and iron-sulfur cluster biosynthesis as key features. Targeted knockdown of the key lipoyltransferase LIPT1 fails to rescue the meiotic defect, whereas supplementation with the NAD + precursor nicotinamide mononucleotide (NMN) improves mitochondrial function and partially restores polar body extrusion. These findings establish cuproptosis as a mechanism linking copper toxicity to mitochondrial impairment and meiotic failure in oocytes, and suggest NAD + metabolism as a potential therapeutic target for protecting oocyte quality.