Unlike mitotic spindles, oocyte meiotic spindles assemble in the absence of centrosomes. This phenomena sparks two interesting questions: 1) how do these acentrosomal spindles arise and 2) what dictates their bipolarity? To better understand acentrosomal oocyte meiotic spindle assembly in C. elegans, we are investigating the requirements for cls-2, a member of the CLASP family of microtubule binding proteins, and the kinesin-14 family members klp-15/16.
Using feeding RNAi mediated knockdown of cls-2 and spinning disk confocal microscopy, we have observed a requirement for CLS-2 during oocyte meiotic spindle assembly, consistent with a previous study1. Interestingly, when using a GFP fusion to the spindle pole marker ASPM-1, we often see only a single focus of GFP::ASPM-1 signal, implying that CLS-2 may play an important role in either establishing or maintaining spindle bipolarity.
The Drosophila orthologue of klp-15/16, non-claret disjunctional (ncd), has been shown to play a role in oocyte meiotic spindle pole assembly, with split or extra poles forming in ncd(-) mutants. However, a role for this kinesin family in C. elegans has not been reported. Using feeding RNAi mediated knockdown of klp-15/16 and spinning disk confocal microscopy, with our GFP::ASPM-1 pole marker, we observed what appears to be diffuse early spindle poles and a late establishment of spindle bipolarity, indicating that a role for this kinesin family in oocyte meiotic spindle pole assembly may be conserved across species.
1. Dumont J, Oegema K, Desai A. Nat Cell Biol. 2010;12(9):894-901.