, 2011 and Jossin and Cooper, 2011), most likely by sequestering cytoplasmic binding partners MK-8776 cell line of endogenous cadherins. Deletion of the binding site for p120ctn within DN-Cdh (Figure 6B) released the dominant-negative effect (Figures 6E and 6F), likely because p120ctn was no longer sequestered, indicating that p120ctn binding to Cdh2 is important for glia-independent somal translocation. The nectin/afadin complex does not bind p120ctn directly, but does so via the small guanosine triphosphatase (GTPase) Rap1, which binds to both afadin and p120ctn (Figure 6A) (Hoshino et al., 2005 and Sato et al., 2006). We hypothesized

that Rap1 might be the crucial link between nectin3 and afadin and Cdh2 and p120ctn pairs. Several lines of evidence support this model. First, Rap1 is required for glia-independent somal translocation, and overexpression

of Cdh2 can rescue the migration defect caused by Rap1 loss of function, demonstrating that Cdh2 acts downstream of Rap1 in this process (Franco et al., 2011). In addition, we now show that a constitutively active form of Rap1 rescued the migration defect caused by nectin3 knockdown (Figures 6C and 6D). Finally, an afadin construct lacking the Rap1 binding site (Figure 6B) acted as a dominant negative and disrupted radial migration Cobimetinib mouse (Figures 6G and 6H). Taken together, our data suggest that nectin3 in migrating neurons recruits an afadin/Rap1 complex that regulates Cdh2 function via p120ctn, thereby promoting leading-process attachment in the MZ and glia-independent somal translocation. At adherens

junctions, cadherins are recruited between neighboring cells through nectin and afadin to form stable adhesions. We therefore reasoned that CR cells might also express Cdh2 that acts in concert with nectin1 to mediate interactions with neurons. Indeed, Cdh2 was expressed in CR cells (Figures 7A and 7B). For functional tests, we electroporated the cortical hem at E11.5 with Dcx-iGFP or Dcx-DN-Cdh-iGFP GPX6 then electroporated the neocortical VZ of the same embryos at E13.5 with Dcx-mCherry to label migrating neurons. By E17.5, GFP+ CR cells had migrated into the neocortical MZ (Figure 7C), while mCherry+ radially migrating neurons populated the emerging CP (Figure 7D). Expression of DN-Cdh did not inhibit the migration of CR cells within the MZ (Figure 7C), but the positions of radially migrating neurons were significantly altered (Figures 7D and 7E). Neurons in controls migrated into the upper CP, whereas large numbers of neurons remained in the lower CP following expression of DN-Cdh in CR cells (Figures 7D and 7E). In addition, neurons in controls had leading processes that branched extensively in the MZ, but branch density was decreased following expression of DN-Cdh in CR cells (Figures 7F and 7G).