Spatio-temporal requirements of Aurora kinase A in mouse oocytes meiotic spindle building

Meiotic spindles are critical to ensure proper chromosome segregation during gamete formation. Oocytes lack centrosomes and use alternative microtubule nucleation pathways for spindle building. However, how these mechanisms are regulated is still unknown. Aurora kinase A (AURKA) is necessary and sufficient for oocyte meiosis in mouse because Aurka KO oocytes arrest in meiosis I [1] and AURKA compensates for loss of Aurkb/Aurkc [2]. AURKA is required early in pro-metaphase I to trigger microtubule organizing center fragmentation, a step necessary to effectively build a bipolar spindle. Moreover, in double Aurkb/Aurkc knockouts, AURKA localizes to spindles and chromatin to support meiosis. Although these mouse models were useful for foundational studies, we were unable to resolve AURKA spatial and temporal functions. Here we provide high-resolution analyses of AURKA requirements during multiple steps of meiotic spindle building and identify the subcellular populations that carry out these functions. By combining mouse genetics and pharmacological approaches we show that AURKA is specifically required in early spindle building and later for spindle stability, whereas AURKC is specifically required in late pro-metaphase. Through expression of targeted AURKA constructs expressed in triple Aurora kinase knockout oocytes and high-resolution live imaging, we demonstrate that the spindle pole population of AURKA is the predominate pool that controls meiotic spindle building and stability.