Fig. 9.

A model for regulation of the morphogenesis of Purkinje cell dendrites by PTN-PTPζ signaling. 1, PTN is produced by Bergmann glia. 2, Before binding to the transmembrane (receptor) form of PTPζ (rPTPζ), PTN may be pooled by binding to the secreted form of PTPζ (Phosphacan) in the extracellular matrix of the ML.3, PTN is suggested to bind with rPTPζ on Bergmann glia. 3′, The possibility that PTN directly binds with rPTPζ on Purkinje cells cannot be excluded. 4, PTPζ signaling controls the formation or maintenance, or both, of the GLAST-positive lamellate processes of Bergmann glia, the mechanism of which is not known at present. 4′, The existence of a GLAST-independent mechanism cannot be excluded. 5, 6, GLAST regulates the extracellular levels of glutamate, which can induce growth or retraction of Purkinje cell dendrites. D, Tyrosine phosphatase domain.