Protocadherins bring cells together

Shining new light on the function of Aurora A A urora A isn’t exactly a mystery protein, but researchers have struggled to determine its function. Hégarat et al. discovered that the kinase helps line up mitotic chromosomes and spurs disassembly of microtubules during anaphase, in collaboration with its cousin Aurora B. Studies on various cell types have furnished contradictory answers about what Aurora A does. Some work suggests that it’s necessary to fashion a bipolar spindle. Other research indicates that absence of the protein stalls the cell in G2, leads to incorrectly aligned chromosomes, or prevents division. To try to nail down the protein’s function, Hégarat et al. deleted the Aurora A gene from cells shortly before mitosis. Although most of the Aurora A–lacking cells constructed a bipolar spindle, their chromosomes often didn’t line up properly. The cells could complete mitosis, but the daughter cells frequently had missing or extra chromosomes, indicating that Aurora A helps to attach kinetochores to opposite spindle poles before chromosome separation. Given Aurora A’s location on the centrosome, how it contributes to chromosome alignment isn’t clear. The scientists also followed cells that lacked Aurora A and Aurora B activity. Early in anaphase, spindle microtubules begin to break down, helping to tug the chromosomes apart. But in the doubly defi cient cells, the microtubules didn’t depolymerize, and chromosomes failed to separate. This result suggests that Aurora A and Aurora B team up to spur microtubule breakdown. Hégarat, N., et al. 2011. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201105058.