Thus, we speculate that protein 4.1, which binds to CASK, promotes the formation of actin/spectrin microfilaments and induces PF protrusions. Nrx also serves as a presynaptic receptor for neuroligins and leucine-rich receptor family members, such as LRRTM1 and LRRTM2 (de Wit et al., 2009; Ko et al., 2009; Siddiqui et al.,

2010). Nevertheless, although triple neuroligin knockout mice exhibit lethal impairments in synaptic transmission, the density of synaptic contact is not altered (Varoqueaux et al., 2006). Since Cbln1 and GluD2 work as a hexamer and a tetramer, respectively, we speculate that the Cbln1-GluD2 complex may induce larger Nrx clusters that may have specific effects on the presynaptic sites. Alternatively, presynaptic proteins other than Nrx may be specifically recruited by the Cbln1-GluD2 complex. We also found that neuronal activity and VAMP2-dependent Selleckchem NSC 683864 exocytosis are essential for the axonal structural changes. Membrane fusion by VAMP2-mediated exocytosis Cobimetinib datasheet has been shown to be essential for the morphological changes in axonal growth cones (Tojima et al., 2007). Such machinery may work together with Nrx-dependent actin rearrangement to induce local PF protrusions.

It is also suggested that Nrx expression and localization themselves are regulated by local transmitter release (Fu and Huang, 2010). These possibilities should be tested in the future to clarify the mechanisms by which PFs undergo structural modifications. aminophylline In addition to Cbln1 and GluD2, other family

proteins, such as Cbln2, Cbln4, and GluD1, are widely expressed in the various brain regions outside the cerebellum (Iijima et al., 2007; Miura et al., 2006). Because Cbln1 also binds to GluD1, and Cbln2 binds GluD1 and GluD2, Cblns-GluDs signaling may function as a global regulator of synapse formation (Matsuda and Yuzaki, 2011). Interestingly, encapsulation of the spines by the axonal terminals has been described in other brain regions during development (Saito et al., 1997). Further studies are warranted to determine whether presynaptic structural changes are induced by Cbln-GluD signaling in various synaptic types, and if so, what mechanisms underlie Cbln-GluD signaling. For details, refer to Supplemental Experimental Procedures. All procedures relating to the animal care and treatment conformed to the institutional guidelines. Electroporation into EGL in vivo was performed as previously described (Konishi et al., 2004). DNA solution was injected into supracerebellar space using glass micropippetes at P7. Forceps-type electrodes were attached to the mouse head and electric pulses (120V, 50 ms, 5 pulses) were applied. To label granule cells in slices, electroporation was performed ex vivo. PCs in the slices were labeled using biolistics. All procedures relating to the animal care and treatment conformed to the institutional guidelines.