Chromosome segregation without spindle microtubules. Peter Vilmos^1*, Szilard Szikora^1,2, Ferenc Jankovics¹, Ildiko Kristo¹, Laszlo Henn¹, Miklos Erdelyi¹. 1) Dept Genetics, Biological Research Center, Szeged, Hungary; 2) Dept Biology, University of Szeged, Szeged, Hungary.

   The prevailing view today is that during eukaryotic cell division chromosome segregation is carried out by spindle microtubules. However, circumstantial evidences support the idea that an actin microfilament-based spindle matrix might play direct role in chromosome movements. To get better insight into the role actin plays in chromosome segregation, we have examined the effect of the depolymerization of F-actin, Tubulin or both during mitosis by using real-time fluorescent in vivo microscopy in early Drosophila melanogaster embryos. Our data show that F-actin together with the microtubules is responsible for the compaction and alignment of the mitotic chromosomes and that it is required for the formation of the microtubule spindles. Moreover, we found that actin filaments are actively participating in chromosome segregation and that the structure marked by the spindle matrix component Chromator might be responsible for chromosome segregation observed in the absence of the mitotic spindle. Our results provide new evidences that actin filaments generate force for chromosome segregation during mitosis.