DNA (blue) is not essential (right) for normal spindle assembly and division (top to bottom) in fly germ cells.
The authors stumbled upon chromosome-independent cell division during a screen for meiosis mutants in Drosophila. Two of the mutants they identified, fusolo and solofuso, had chromosome segregation defects that led to secondary spermatocytes lacking chromosomes. Nonetheless, these male germ cells constructed normal centrosome-nucleated astral arrays and a typical central spindle, appropriately containing the cell cleavage protein Aurora B. A contractile ring including the usual components of the cytokinetic apparatus (such as F-actin and myosin II) formed around the midzone in the mutants, and cytokinesis progressed as in wild-type cells.
Unlike in fly spermatocytes, in all other systems studied so far,...
