Fig. 7. Schematic comparison of cell sorting processes occuring during hindbrain segmentation and striatal compartmentalization. (A) In the developing hindbrain, neural cells generated from adjacent rhombomeric segments express repulsive ephrin ligands (in red) or Eph receptors (in green) in a mutually exclusive pattern. This allows a strict restriction of cell intermingling that results in the characteristic segmented pattern of the rhombomeres. (B) In the developing striatum, striosome neurons (S) are generated first (t1) and express high levels of ephrin ligands (in red) and low levels of Eph receptors (in green). Matrix neurons are generated later (t2) and express high levels of receptors and low levels of ligands. Matrix and striosome cells first intermix and then partially segregate, through the effects of bidirectional interactions, to form the mature mosaic pattern of the striatum (t3). See text for further discussion.