Fig. 1. klp67A mutant primary spermatocytes lack robust central spindles and midbodies. (A) Late anaphase cells isolated from klp67A mutants or wild-type (inset) testes. Microtubules are in green, DNA in blue and the centriole marker Centrin in red. During late anaphase control cells form a symmetrical central spindle that spans the cell's equator. In klp67A mutants the central spindles are diminished and asymmetrical with microtubule bundles positioned on a single side of the cell (white arrowhead) or concentrating in the interior but lacking at the periphery (white arrow). Some centrosome-associated MTs can be abnormally long and run along the periphery (black arrowhead). In other cells, the spindles become bent or S-shaped (black arrow). (B) In control cells constriction of the contractile ring results in the formation of a dense midbody connecting the two daughter cells (inset). This structure was rarely observed in the mutant cells, which although partially constricted lacked discreet microtubule bundles at this later stage. Note how most cells homogenously contain individual, disorganised microtubules but that in some instances few microtubules are visible at the equator (arrowhead). Bar, 10 µm.