Haspin kinase regulates microtubule-organizing center clustering and stability through Aurora kinase C in mouse oocytes

Abstract

Meiotic oocytes lack classic centrosomes and, therefore, bipolar spindle assembly depends on clustering of acentriolar microtubuleorganizing centers (MTOCs) into two poles. However, the molecular mechanism regulating MTOC assembly into two poles is not fully understood. The kinase haspin (also known as GSG2) is required to regulate Aurora kinase C (AURKC) localization at chromosomes during meiosis I. Here, we show that inhibition of haspin perturbed MTOC clustering into two poles and the stability of the clustered MTOCs. Furthermore, we show that AURKC localizes to MTOCs in mouse oocytes. Inhibition of haspin perturbed the localization of AURKC at MTOCs, and overexpression of AURKC rescued the MTOC-clustering defects in haspin-inhibited oocytes. Taken together, our data uncover a role for haspin as a regulator of bipolar spindle assembly by regulating AURKC function at acentriolar MTOCs in oocytes.

The Mitotic Protein Kinase Haspin and Its Inhibitors

“…Inhibition of Haspin by 5-ITu showed a failure to organize microtubules and an increase in microtubule organizing centers (MTOCs) as well as an impaired localization of Aurora C at this location. These results suggested a new role for Haspin in the regulation of MTOCs clustering during meiosis and Aurora C localization at MTOC supporting the idea of different functions of Haspin in meiosis compared to mitosis [30].…”

“…GFP:Haspin co-localizes with chromatin and H3T3ph during all meiotic stages [29,30]. Notably, H3T3ph levels were increased with overexpression of exogenous Haspin, thus confirming that Haspin phosphosphorylates H3T3 in oocytes.…”

“…Haspin was also weakly detected as filamentous aggregates on the spindle. At anaphase I/telophase I transition, Haspin is translocated from chromosomes to midbody [29,30].…”

“…Furthermore, Haspin phosphorylation on H3T3 has been shown to be required for Aurora C kinase proper localization during meiosis [29,46]. During meiosis I, in contrast to mitosis, where Haspin is involved in CPC targeting to centromeres, Haspin regulates Aurora C localization to the inter-chromatid axis [29,30]. Inhibition of Haspin by 5-ITu showed a failure to organize microtubules and an increase in microtubule organizing centers (MTOCs) as well as an impaired localization of Aurora C at this location.…”

The chromosomal basis of meiotic acentrosomal spindle assembly and function in oocytes

“…AURKC localizes to centromeres and chromosome arms during metaphase I and is restricted to centromeres at metaphase II, whereas AURKB localizes to microtubules (Balboula and Schindler 2014; Sharif, et al 2010; Shuda, et al 2009). A recent finding is that AURKC is recruited to spindle poles by Haspin kinase and is required for MTOC clustering (Balboula, et al 2016). However, in oocytes from Aurkc −/− mice, AURKB compensates, adopting AURKC localization and activity (Balboula and Schindler 2014; Schindler, et al 2012).…”