Fig. 7. The molecular mechanisms by which CBF1 controls the expression of topographic molecules. (A) Schematic representation of modes of actions of CBF1. Ephrin A5 and ephrin A2 are controlled by CBF1 through transcriptional repression and a DNA binding-independent mechanism, respectively. However, the others are controlled through the dual mechanisms of CBF1. One Ephephrin system is controlled as a set by each mode of CBF1 action. (B) Expressional regulation of asymmetrically distributed molecules along the NT axis by CBF1. CBF1 and Ventroptin repress expression of BMP2 by inhibiting BMP signaling as an interrupter and antagonist, respectively, and induce ephrin A2 expression. However, CBF1 represses the transcription of negative regulators, X and Y. When CBF1 is absent, X downregulates ephrin A5 expression, and Y represses expression of SOHo1 and GH6. When CBF1 is present, X and Y are downregulated, and the expression of ephrin A5, SOHo1 and GH6 is induced. SOHo1 and GH6 inhibit the expression of EphA3. EphA3 and ephrins are directly implicated in the control of axon guidance. CBF1 also represses CBF2 expression. However, downstream target genes of CBF2 have not been identified so far. See text for details.