College of Animal Science and Technology, Nanjing Agricultural University, Weigang 1, Nanjing, China.
Biol Reprod. 2020 May 26;102(6):1203-1212. doi: 10.1093/biolre/ioaa033.
Formin-like 3 (FMNL3) is a member of the formin-likes (FMNLs), which belong to the formin family. As an F-actin nucleator, FMNL3 is essential for several cellular functions, such as polarity control, invasion, and migration. However, the roles of FMNL3 during oocytes meiosis remain unclear. In this study, we investigated the functions of FMNL3 during mouse oocyte maturation. Our results showed that FMNL3 mainly concentrated in the oocyte cortex and spindle periphery. Depleting FMNL3 led to the failure of polar body extrusion, and we also found large polar bodies in the FMNL3-deleted oocytes, indicating the occurrence of symmetric meiotic division. There was no effect of FMNL3 on spindle organization; however, we observed spindle migration defects at late metaphase I, which might be due to the decreased cytoplasmic actin. Microinjecting Fmnl3-EGFP mRNA into Fmnl3-depleted oocytes significantly rescued these defects. In addition, the results of co-immunoprecipitation and the perturbation of protein expression experiments suggested that FMNL3 interacted with the actin-binding protein FASCIN for the regulation of actin filaments in oocytes. Thus, our results provide the evidence that FMNL3 regulates FASCIN for actin-mediated spindle migration and cytokinesis during mouse oocyte meiosis.
formin 样蛋白 3（FMNL3）是formin 样蛋白（FMNLs）家族的一员，属于formin 家族。作为 F-肌动蛋白核酶，FMNL3 对于细胞的多种功能至关重要，如极性控制、侵袭和迁移。然而，FMNL3 在卵母细胞减数分裂中的作用尚不清楚。在这项研究中，我们研究了 FMNL3 在小鼠卵母细胞成熟过程中的作用。我们的结果表明，FMNL3 主要集中在卵母细胞皮质和纺锤体周围。耗尽 FMNL3 导致极体挤出失败，并且我们还发现 FMNL3 缺失的卵母细胞中有大的极体，表明发生了对称的减数分裂。FMNL3 对纺锤体组织没有影响；然而，我们观察到在中期 II 末期纺锤体迁移缺陷，这可能是由于细胞质肌动蛋白减少所致。将 Fmnl3-EGFP mRNA 微注射到 FMNL3 耗尽的卵母细胞中可显著挽救这些缺陷。此外，共免疫沉淀和蛋白表达实验的扰动结果表明，FMNL3 与肌动蛋白结合蛋白 FASCIN 相互作用，以调节卵母细胞中的肌动蛋白丝。因此，我们的结果提供了证据表明，FMNL3 通过调节 FASCIN 来调节肌动蛋白介导的纺锤体迁移和卵母细胞减数分裂中的胞质分裂。
