Figure 10
From: Semaphorin-6A controls guidance of corticospinal tract axons at multiple choice points
A model for corticospinal tract (CST) guidance at the inferior olive (io) and decussation. CST axons (blue) express PlxnA4. At the level of the olive they are constrained medially in wild-type animals by the expression of Sema6A (cyan, top left). (Note that the olives also express PlxnA4.) Further caudally, this allows the CST axons to respond to cues for decussation (bottom left). In Sema6A or PlxnA4 mutants (right) the CST axons are not constrained by the inferior olives and a proportion of axons adopt a more lateral position or extend within the olives themselves (top right). At the level of the decussation (bottom right) many CST axons are too far away from the midline to respond to decussation cues and continue to extend in a ventrolateral position. Those that remain near the midline may decussate normally.