Cell migration and orientated cell division contribute to the spatial distribution of cells. Careful analysis of fly wild-type and mutant embryonic organ precursors for orientation of cell division implicates such orientation in determining organ morphology and points to planar cell-polarity genes as important players in this process.

The authors analysed the orientation of cell divisions in marked clones within imaginal discs — the epithelial, embryonic precursors of adult fly organs. They found a correlation between the orientation of cell divisions and the shape of the clones (and ultimately the adult organs); the correlation persisted throughout development.

Planar cell-polarity genes are known to define the polarity of cells within an epithelium, and flies that carry mutations in members of this family, such as dachsous and fat, have abnormally shaped organs. The authors show that this dismorphology is associated with changes in the orientation of cell division.

This work might have uncovered a general mechanism of organ morphogenesis: there is a correlation between the orientation of cell division and the shape of different organs and, importantly, planar cell-polarity genes are well-conserved throughout evolution. We now need specifically targeted experiments to confirm this possibility.