We determined that the overexpression of WT-DISC1 led to a small increase in cAMP levels; however, it was not statistically significant (Figure S3B). Evaluation of the different
DISC1 variants in this assay further revealed no difference in cAMP levels compared with GFP controls. Therefore, our data suggest that the DISC1 variants do not specifically regulate cAMP levels in a dominant-negative manner. Taken together, the analysis of human LCLs demonstrates that the R264Q variant directly regulates Wnt signaling by regulating the activation of Wnt signaling proteins. Since all of our studies suggest the S704C variant does not affect Wnt signaling or neural progenitor proliferation, we hypothesized this variant might regulate another Wnt-independent
neurodevelopmental event. Since this variant lies in the C terminus of DISC1, which interacts with selleck compound the neuronal migration genes Ndel1 and Dix domain containing 1 (Dixdc1), we asked whether it alters the migration the newborn neurons. Using in utero electroporation, we tested the ability of WT-DISC1 versus the DISC1 variants to rescue the neuronal migration defect caused by downregulation of DISC1. We found that first, expression of human WT-DISC1 rescues the GFP-positive cells that are normally arrested in the intermediate and subventricular zones due to DISC1 downregulation, restoring their migration to the upper layers of the cortex, similar to control shRNA (Figure 6A). We then tested the different DISC1 find more variants in this paradigm and found that the A83V, R264Q, and L607F variants functioned similar to WT-DISC1 Endonuclease and
also restored the migration of arrested GFP-positive cells to the upper cortical layers (Figure 6A). However, we determined that the S704C variant was not able to completely restore migration, since there a significant number of GFP cells still remaining in the VZ/SVZ and IZ compared with the other conditions, suggesting this C-terminal variant is required for neuronal migration (Figure 6A). Given that we found the S704C variant affects neuronal migration, we asked whether overexpression of this variant alone could cause a neuronal migration defect in a dominant-negative fashion. We overexpressed the different DISC1 variants and found that only the S704C variant disrupted neuronal migration compared with the other DISC1 variants, demonstrating S704C has consistent effects on migration using two different experimental paradigms (Figure S4). To determine the mechanism by which the S704C variant inhibited migration, we hypothesized this variant might have disrupted interaction with Ndel1 and/or Dixdc1, and therefore tested the ability of all the variants to bind these molecules. Interestingly, we found that there was reduced binding between the S704C variant and Dixdc1, but not Ndel1 (Figures 6B and 6C), whereas all other DISC1 variants all had equal interaction with Ndel1 and Dixdc1.