Abstract
Background: Disrupted-in-schizophrenia 1 (DISC1) regulates neurogenesis and is a genetic risk factor for major psychiatric disorders. However, how DISC1 dysfunction affects neurogenesis and cell cycle progression at the molecular level is still unknown. Here, we investigated the role of DISC1 in regulating proliferation, migration, cell cycle progression and apoptosis in mouse neural stem/progenitor cells (MNSPCs) in vitro.Methods: MNSPCs were isolated and cultured from mouse fetal hippocampi. Retroviral vectors or siRNAs were used to manipulate DISC1 expression in MNSPCs. Proliferation, migration, cell cycle progression and apoptosis of altered MNSPCs were analyzed in cell proliferation assays (MTS), transwell system and flow cytometry. A neurogenesis specific polymerase chain reaction (PCR) array was used to identify genes downstream of DISC1, and functional analysis was performed through transfection of expression plasmids and siRNAs.Results: Loss of DISC1 reduced proliferation and migration of MNSPCs, while an increase in DISC1 led to increased proliferation and migration. Meanwhile, an increase in the proportion of cells in G0/G1 phase was concomitant with reduced levels of DISC1, but significant changes were not observed in the number MNSPCs undergoing apoptosis. Paired box gene 5 (Pax5), sex determining region Y-box 2 (Sox2), delta-like1 (Dll1) and Neurogenin2 (Neurog2) emerged as candidate molecules downstream of DISC1, and rescue experiments demonstrated that increased or decreased expression of either molecule regulated proliferation and migration in DISC1-altered MNSPCs.Conclusion: These results suggest that Pax5, Sox2, Dll1 and Neurog2 mediate DISC1 activity in MNSPC proliferation and migration.
Highlights
Until recently, many psychiatric disorders were undefined at the molecular level
Using room temperature (RT)-polymerase chain reaction (PCR), decreases in endogenous mRNA levels of disruptedin-schizophrenia 1 (DISC1), Paired box gene 5 (Pax5), sex determining region Y-box 2 (Sox2), Dll1 and Neurog2 were observed in mouse neural stem/progenitor cells (MNSPCs)
We found that in CAGDISC1 MNSPCs, up-regulation of Pax5 increased proliferation by 2.7%, 9.8%, and 12.3% after 24 h, 48 h and 72 h. These results suggest that Pax5 regulates the proliferation of MNSPCs independent of DISC1 (Figures 3D–F)
Summary
Many psychiatric disorders were undefined at the molecular level. These included schizophrenia (SZ; Le Strat et al, 2009), bipolar disorder (Blackwood et al, 2001b), major depressive disorder (Brandon et al, 2009) and epilepsy (Fournier et al, 2009, 2010). The molecular interaction network involving DISC1 has been referred to as the ‘‘DISC1 interactome’’ and plays a major role in neurogenesis and neural development (Figure 1A; Camargo et al, 2007; Korth, 2009) Members of this network include DISC1 binding partners such as Nuclear distribution protein nudE-like 1 (NDEL1), Fasciculation and elongation protein zeta-1 (FEZ1), lissencephaly (LIS1), Glycogen synthase kinase 3 beta (GSK3β), Girdin, Dixdc (Dixin), Growth factor receptor-bound protein 2 (Grb2), Ras homolog enriched in the brain 1 (Rheb1) and intracellular/extracellular signaling pathways, such as the AKT-mTOR, ERK, GSK3β, Wnt, NMDA-R, Reelin and GABA pathways (Fournier et al, 2010; Kang et al, 2011, 2015; Kim et al, 2012; Wu et al, 2013). We investigated the role of DISC1 in regulating proliferation, migration, cell cycle progression and apoptosis in mouse neural stem/progenitor cells (MNSPCs) in vitro
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