Luo, S.-M. | Search bioRxiv

bioRxiv2023

FMNL2 regulates actin for ER and mitochondria distribution in oocyte meiosis

During mammalian oocyte meiosis, spindle migration and asymmetric cytokinesis are unique steps for the successful polar body extrusion. The asymmetry defects of oocytes will lead to the failure of fertilization and embryo implantation. In present study we reported that an actin nucleating factor formin-like 2 (FMNL2) played critical roles in the regulation of spindle migration and organelle distribution. Our results showed that FMNL2 mainly localized at the oocyte cortex and periphery of spindle. Depletion of FMNL2 led to the failure of polar body extrusion and large polar bodies in oocytes. Live-cell imaging revealed that the spindle failed to migrate to the oocyte cortex, which caused polar body formation defects, and this might be due to the decreased polymerization of cytoplasmic actin by FMNL2 depletion. Furthermore, mass spectrometry analysis indicated that FMNL2 was associated with mitochondria and endoplasmic reticulum-related proteins, and FMNL2 depletion disrupted the function and distribution of mitochondria and endoplasmic reticulum, showing with decreased mitochondrial membrane potential and the occurrence of endoplasmic reticulum stress. Microinjecting Fmnl2-EGFP mRNA into FMNL2-depleted oocytes significantly rescued these defects. Thus, our results indicate that FMNL2 is essential for the actin assembly, which further involves into meiotic spindle migration and ER/mitochondria functions in mouse oocytes.

developmental biology↗

bioRxiv2020

Double-strand breaks can induce DNA replication and damage amplification in G2 phase-like oocytes of mice

Break-induced DNA replication (BIR) have been detected not only in the genome of rare disease patients but also in cancer cells, however, the mechanisms of BIR formation havent been explained in details. In the late G2 phase-like mouse oocytes, we found DNA double-strand breaks (DSBs) could induce Rad51 dependent small-scale DNA replication. In addition, we also found the DSBs could be amplified in mouse oocytes, and the amplification could be inhibited by Rad51 inhibitor IBR2 and DNA replication inhibitor ddATP. Lastly, we found the DSB repair was relatively inefficiency in hybrid mouse oocytes compared with that of the purebred mouse oocytes. We found DSBs could induce BIR more easier in hybrid mouse oocytes, indicating the DNA repair in oocytes could be affected by the sequence differences between homologous chromatids. In summary, our results indicated that the condensed chromatin configuration in late G2 phase and the sequence similarity between broken DNA and template DNA are causing factors of BIR in mammalian genome, and the DNA damage could be amplified in late G2 phase cells.

genetics↗