FOCAL POINT  Two groups investigate how the microcephaly-associated protein Asp organizes mitotic spindles. (Top row, left to right) Gohta Goshima and Ami Ito reveal that Asp focuses spindle poles by cross-linking microtubule minus ends at the poles and within the spindle. Spindle microtubules (red) are focused at the poles in Drosophila S2 cells expressing full-length Asp (green, left) but unfocused in cells that instead express a C-terminally truncated version of the protein (green, right). Meanwhile (bottom row, left to right), Nasser Rusan, Todd Schoborg, and colleagues reveal that the association of calmodulin with Asp’s C-terminal domain is crucial for the proteins’ mutual function in pole focusing and centrosome attachment. In the neuroblasts of an asp-null fly, pole focusing is restored by full length Asp (left) but not by an Asp mutant unable to bind calmodulin (right). Calmodulin is not required for Asp’s ability to promote brain growth, however.

PHOTO COURTESY OF THE AUTHORS