Inhibition of BLM helicase disrupts organelle function and oocyte maturation in goats.

During the first meiotic division, oocytes inevitably undergo physiological DNA double-strand breaks (DSBs), which are primarily repaired through Bloom (BLM) helicase-mediated homologous recombination repair (HRR). This study investigated the consequences of BLM helicase suppression on meiotic maturation in goat oocytes, revealing that BLM helicase exhibited nuclear-predominant expression over cytoplasmic localization during meiosis I/meiosis II stages and colocalized with spindle fibers. Functional impairment of BLM helicase blocked oocyte maturation, accompanied by dysregulated expression of cumulus expansion-related genes, downregulation of oocyte paracrine factors, elevated reactive oxygen species accumulation, compromised mitochondrial function, upregulated endoplasmic reticulum stress-responsive genes, impaired autophagolysosomal activity, and disrupted Golgi distribution and ribosome function, though mitochondrial fusion and fission remained unaffected. Transcriptomics and reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis further demonstrated that the inhibition of BLM significantly downregulated expression of HRR-associated genes (REC8, PPP4C) while upregulating non-homologous end joining-associated genes (DCLRE1B, ERCC4), suggesting that BLM helicase deficiency may shift DSB repair from HRR to error-prone non-homologous end joining. Consistently, immunofluorescence staining revealed a significant increase in the DNA damage response factor phosphorylated ATM and the repair protein RAD51, indicating that BLM inhibition induces substantial DNA damage in oocytes. These results demonstrate that BLM plays a critical role in maintaining nuclear genomic stability in oocytes. This study highlights BLM helicase as a critical regulator of organelle homeostasis during meiotic progression and provides novel mechanistic insights into its multifaceted roles in oocyte maturation.