However, the Ser704Cys (S704C) variant does not affect Wnt signaling but does inhibit neuronal migration via a cytoskeleton signaling pathway. These results provide insight into the normal function of DISC1 genetic variation, and suggest that brain structural and functional phenotypes associated selleck chemical with DISC1 variants may arise due to their disruptive effects on specific signaling pathways during brain development. To discover different human DISC1
variants, we performed deep-sequencing of all DISC1 exons (exome sequencing) on 717 individuals (166 bipolar disorder, 203 schizophrenia, and 369 control individuals). We initially identified common and rare DISC1 variants within this sample set and subsequently genotyped additional healthy individuals and patients as part of a larger study (∼16,500 individuals). From the identified variants, we selected a subset of rare and
common variants to determine their impact on canonical Wnt signaling (Table 1 and data not shown). We focused on the common variants R264Q, L607F, BMS-387032 nmr and S704C specifically since they have been associated with brain structural and psychiatric behavioral phenotypes. We also tested the function of different rare DISC1 variants that were closer to the N terminus since this is one of the regions of DISC1 that binds to GSK3β (data not shown) (Mao et al., 2009). We specifically focused on assaying the function of one rare variant for all experiments, A83V, in order to test its ability to bind GSK3β and modulate Wnt signaling and neural progenitor proliferation. Furthermore, although our initial DISC1 exome sequencing suggested some common and rare variants might be enriched in SZ or BPD populations, larger genotyping efforts revealed there was no statistically significant bias for variants associated with SZ or BPD. To determine if DISC1 variants regulate Wnt
signaling, we performed in vitro assays to measure Wnt-induced T Cell Factor/Lymphoid Enhancer Factor (TCF/LEF) transcriptional activity. We have previously reported that overexpressing mouse wild-type (WT)-mDISC1 can significantly Sodium butyrate potentiate 16 hr Wnt-induction of TCF/LEF activity in HEK293 cell lines (Mao et al., 2009). Using this result as our reference, we tested whether the human DISC1 variants also potentiated TCF/LEF activity similarly to WT-human DISC1 (WT-DISC1). Interestingly, we found that the majority of the rare DISC1 variants, including A83V, and the common R264Q and L607F variants unable to potentiate TCF/LEF activity compared with WT-DISC1, as they performed no different than GFP controls (Figure 1A, data not shown). However, the S704C common polymorphism was able to significantly potentiate activity, suggesting that it does not display loss of function activity. It is possible these results could arise due to differences in expression levels of the different hDISC1 variants.