To examine the effects of integrin α5β1 in the eventual pattern of neuronal alignment in the mature cortex, we performed sequential in utero electroporation (Sekine et al., 2011). We introduced a GFP-expression vector at E14.5 to label the earlier-born neurons. Since the

find more length of the cell cycle at this stage is about 15–16 hr (Takahashi et al., 1995), we electroporated a control vector, an integrin α5 KD vector, or an integrin β1 KD vector along with an mCherry-expressing vector 16 hr after the first electroporation to label the later-born neurons in the same cortex. At P7, when all the neuronal layers are established, the control-control case showed a clearly segregated birthdate-dependent inside-out pattern (Figures 7A and 7A′). In contrast, this highly segregated inside-out pattern of neuronal alignment was significantly disrupted in the control-integrin α5 KD or control-integrin β1 KD cases (Figures 7B–7D). These data suggest that the terminal translocation failure JQ1 supplier caused by integrin α5 or β1 KD results in the disruption of the final pattern of neuronal positioning in the mature cortex. The bidirectional interactions between migrating cells and their surrounding environment are fundamental for the establishment of functional multicellular organ systems,

and are also closely involved in the pathogenesis of several diseases such as metastases and inflammatory diseases. In many cases, environmental factors play central roles to influence the behaviors of migrating cells in a spatiotemporal manner. Integrin receptors are also important for this bidirectional interaction, because integrins can transmit the signals between the outside and inside of the

cells (Hynes, 2002). In this study, we identified that Reelin, as an extrinsic factor, switches the function of Rap1 during terminal translocation and thereby activates integrin α5β1 through the biologically conserved inside-out signaling cascade (Shattil et al., AZD7545 2010). We also found that this integrin activation changes the neuronal migration mode by promoting neuronal adhesion to the ECM protein, such as fibronectin, and that this interplay between migrating neurons and the ECM is crucial to establish the eventual birthdate-dependent layering pattern of neurons in the mature cortex (Figure 8). The roles of the integrin family in the neuronal migration in the neocortex have been under debate (Belvindrah et al., 2007; Anton et al., 1999; Dulabon et al., 2000; Magdaleno and Curran, 2001; Schmid et al., 2004; Sanada et al., 2004; Luque, 2004; Marchetti et al., 2010). It was reported using knockout mice that integrin β1 in neurons was not required for layer formation (Belvindrah et al., 2007), whereas integrin α3, which heterodimerizes only with integrin β1, was expressed below the CP and was required for neuronal migration (Anton et al., 1999; Dulabon et al., 2000; Schmid et al., 2004).