Modeling Planarian Regeneration: A Primer for Reverse-Engineering the Worm
Figure 3
Planaria restore their AP polarity similarly to bar magnets.
(A) A bar magnet restores the original polarity after being cut transversally. (B) Similarly, after bisecting a worm, polarity is restored correctly in each fragment. Note that even though cells on either side of the amputation plane were direct neighbors before the cut, the ones facing posterior make a completely different structure (a tail) than the ones facing anterior (a head). The drastically different fates of cells with essentially the same positional information suggest models based on non-local control of orientation [8].