These findings suggest that the signal transductions mediated by CS proteoglycans are involved in the directed outgrowth of neurites, although it is not known what kinds of CS proteoglycans contribute to these phenomena. a glutamate transporter inhibitor also induced the irregular morphogenesis of Purkinje cell dendrites. Altogether, these findings suggest that PTN-PTP signaling regulates the morphogenesis of Purkinje cell dendrites and that the mechanisms underlying that rules involve the GLAST activity in Bergmann glial processes. having a single primary dendrite extending in only one direction. This suggests that the polarity of Purkinje cells is determined by alternative mechanisms. Recently, Yamada et al. (2000)found that the lamellate processes of Bergmann glia surrounded the differentiating dendritic trees of Purkinje cells, and more importantly, the growing suggestions of Purkinje cell dendrites came into the external granular coating (EGL) by contacting DKK2 the rod-like processes of Bergmann glia. These observations suggest that the Bergmann gliaCPurkinje cell connection is definitely involved in the directed growth and dedication of polarity of Purkinje cell dendrites. Phosphacan/6B4 proteoglycan, a chondroitin sulfate (CS) proteoglycan indicated mainly in the CNS, is definitely distributed round the cell surface of Purkinje cells during dendritic outgrowth (Maeda et al., 1992). Phosphacan corresponds to the extracellular website of PTP/RPTP, a receptor-type protein tyrosine phosphatase composed of an N-terminal carbonic anhydrase-like website, a fibronectin type III website, a serine-, glycine-rich website, a transmembrane section, and two intracellular tyrosine phosphatase domains (Maurel et al., 1994;Peles et al., 1998). Phosphacan and the transmembrane-type molecules are generated by alternate splicing, and all the splice Mitochonic acid 5 variants are synthesized as CS proteoglycans (Maurel et al., 1994; Nishiwaki et al., 1998; Peles et al., 1998). Pleiotrophin (PTN) and midkine (MK), closely related heparin-binding growth factors, bind to PTP/phosphacan with high affinity and result in signal transduction of this receptor (Maeda et al., 1996, 1999). The CS portion of PTP/phosphacan takes on an essential part in binding to PTN and MK, and the removal of CS chains from PTP/phosphacan resulted in a marked decrease of the binding affinity to PTN and MK and in the loss of transmission transduction (Maeda et al., 1996, 1999; Qi et al., 2001). Although Purkinje cells and Bergmann glia communicate PTP/phosphacan (Canoll et al., 1993; Snyder et al., 1996), PTN and MK distribute along Bergmann glial materials in postnatally developing cerebellum (Matsumoto et al., 1994; Wewetzer et al., 1995). These manifestation patterns suggest that PTN/MK secreted by Bergmann glia binds with PTP on Purkinje cells or Bergmann glia, or both. Therefore, the signaling of PTP/phosphacan and PTN/MK could be involved in cellCcell connection between Purkinje cells and Bergmann glia. In this study, we hypothesized that PTN-PTP signaling is definitely involved in the Bergmann gliaCPurkinje cell connection required for the morphogenesis of Purkinje cell dendrites. To test this hypothesis, we used organotypic slice cultures of postnatal rat cerebellum, which preserve the cytoarchitecture of the cerebellar cortex and reproduce the series of processes in cerebellar cortical development (Tanaka et al., 1994). Using this system, we found that the perturbation of PTN-PTP signaling resulted in a Mitochonic acid 5 marked increase in the number of Purkinje cells with irregular dendrites, such as multiple and disoriented main dendrites, showing that PTN-PTP signaling is definitely involved in the morphogenesis of Purkinje cell dendrites. Furthermore, we acquired evidence suggesting Mitochonic acid 5 that Bergmann glia play important tasks in these mechanisms. Materials and Methods (DIV). The cultures were incubated at 33C in 5% CO2/95% air flow. Because a large number of cells degenerated in the bottom part (medium side) of the slice cultures, we analyzed the top half (air part) to obtain data in the present study. test. for 15 min at 4C, the supernatants (15 g protein) were.