NDC1 is required for nuclear pore complex organization and meiotic progression in mouse oocytes

Nuclear pore complexes (NPCs) mediate nucleocytoplasmic transport. NDC1 is a transmembrane nucleoporin involved in NPC assembly, but its role in mammalian oocyte meiosis remains unclear. In this study, we demonstrated that NDC1 was essential for normal oocyte maturation. Using Gdf9 -Cre to delete Ndc1 in mouse oocytes, we found that Ndc1 loss caused female sterility, delayed germinal vesicle breakdown, meiosis I arrest, and severe spindle defects. Ndc1 cKO oocytes showed a marked loss of ALADIN protein and nuclear envelope signal, reduced nuclear envelope enrichment of NUP160, and fewer morphologically identifiable NPCs. Abnormal ALADIN and NUP160 localization was already evident in growing oocytes from postnatal day 14 mice. Nuclear accumulation of Cyclin B1 and an SV40 NLS reporter was delayed in Ndc1 cKO oocytes, although nuclear import was not completely blocked. Ndc1 deletion also altered the distribution of the RBD-mCherry RanGTP reporter and endogenous importin β. During early spindle assembly, TPX2 fluorescence in the spindle region and phosphorylated PLK1 fluorescence at acentriolar microtubule organizing centers increased, whereas phosphorylated Aurora A fluorescence at these sites decreased. These findings show that NDC1 is required for normal NPC organization and meiotic progression in mouse oocytes. Impaired nuclear import and changes in several spindle regulators may contribute to the meiotic defects after Ndc1 loss.