last updated April 2013
Managing the great cell divide
A massive screen of enzymes reveals a pathway that helps ensure that dividing cells each receive their fair share of chromosomes
In every cell division, the genetic material must be partitioned equally, with each ‘daughter cell’ receiving a copy of each chromosome. This is coordinated by structures called spindles, which form at either end of the cell and use protein fibers to reel in the chromosomes. Immediately prior to cell division, spindles must arrange precisely in orderly pairs at the center of the cell. Now, recent work from a team led by Fumiko Toyoshima at Japan’s Kyoto University has revealed a key mechanism that mammalian cells use to achieve this positioning1.
Enzymes called kinases play a key management role in the cell, issuing important instructions to other proteins, Toyoshima’s team began by observing the effects of eliminating expression of different kinases on spindle orientation in cultured cells. This work revealed that the ABL1 kinase helps organize the spindles along an axis parallel to the surface on which cells are growing.
Subsequent experiments revealed that ABL1 regulates localization of two other spindle-alignment proteins, NuMA and LGN. Without ABL1, NuMA fails to accumulate near the cell membrane while LGN gathers there in excess, and the spindles become markedly misoriented. Given that both ABL1 and spindle misalignment have been linked to cancer, further characterization of this pathway may prove clinically useful in the future.