Oriented divisions, fate decisions.

During development, the establishment of proper tissue architecture depends upon the coordinated control of cell divisions not only in space and time, but also direction. Execution of an oriented cell division requires establishment of an axis of polarity and alignment of the mitotic spindle along this axis. Frequently, the cleavage plane also segregates fate determinants, either unequally or equally between daughter cells, the outcome of which is either an asymmetric or symmetric division, respectively. The last few years have witnessed tremendous growth in understanding both the extrinsic and intrinsic cues that position the mitotic spindle, the varied mechanisms in which the spindle orientation machinery is controlled in diverse organisms and organ systems, and the manner in which the division axis influences the signaling pathways that direct cell fate choices.