Increased DA secretion from SZ hiPSC neurons is consistent w

Increased DA secretion from SZ hiPSC neurons is consistent with the ability of current antipsychotics, functioning as D2 DA receptor antagonists, to ameliorate the positive symptoms of SZ (Seeman, 1987; Coyle and Konopask, 2012; Eyles et al., 2012). Interestingly, because current antipsychotics lack efficacy for improving the cognitive dysfunction of SZ (Heinrichs and Zakzanis, 1998; Young et al., 2012; Coyle and Konopask, 2012), it is possible that neurotransmitters other than DA contribute to SZ such as those identified in hiPSC neuronal models. Other neurotransmitter systems involved in SZ may include glutamate (Snyder and Gao, 2013; Menniti et al., 2013), serotonin (Meltzer et al., 2012), and GABA (Volk and Lewis, 2013). It will be advantageous in future studies to characterize the activity-dependent release of these other neurotransmitter systems in SZ hiPSC neurons. Great progress has been achieved in recent years in development of hiPSC neuronal systems to model human order tranylcypromine diseases (Kiskinis and Eggan, 2010; Brennand et al., 2011; Young and Goldstein, 2012; Peitz et al., 2013). The ability to investigate the critical property of activity-dependent neurotransmitter release from hiPSC neurons derived from patients afflicted with mental disorders and neurological diseases can provide knowledge of chemical neurotransmitter mechanisms in brain disorders.
Experimental Procedures
Acknowledgments
Introduction In recent years, the idea of directly converting one somatic cell type into another has attracted substantial attention because it offers a valuable source for cells that are difficult to access (Vierbuchen and Wernig, 2011). However, a major drawback linked to current strategies is the fact that they are based on ectopic expression of key developmental genes that often have to be stably integrated into the genome. Despite the possibilities to tightly control ectopic gene expression, such genetic modifications may have undesired effects. Small molecules specifically modifying key signaling pathways provide a powerful tool to enhance conversion or even replace reprogramming genes. Recently, the generation of pluripotent stem cells in mouse by small molecules has been reported (Hou et al., 2013). However, chemical conversion of human cells has thus far only been demonstrated for the generation of endodermal cells (Pennarossa et al., 2013).
Results
Discussion In our approach, conversion to Schwann cells was induced by sequential treatment with defined compounds. First, a brief VPA treatment step probably resulted in an erase of epigenetic signatures making cells more amenable for cell-fate changing signals—a process that may also be involved in gene-free iPS generation or transdifferentiation into endodermal cells (Hou et al., 2013; Pennarossa et al., 2013). Fate determination toward transient precursors was achieved by treatment with CB inhibiting AMPK, MSK1, PKA, ROCK2, PKGa, and SGK1. Several studies of these signaling pathways allow assumptions regarding the mechanistic regulation of the conversion process. Because upregulation of SGK1 correlates with cell death in neurodegenerative disease (Schoenebeck et al., 2005), its inhibition might enhance the survival of cells that converted toward a neural fate. Moreover, CB might abolish a metabolic barrier mediated by AMPK signaling, which is known to prevent reprogramming processes (Vazquez-Martin et al., 2012). ROCK2 inhibition evokes a proliferative, stem cell-like phenotype (Terunuma et al., 2010), promotes emigration of neural crest cells (Groysman et al., 2008), and has neuroprotective effects (Ding et al., 2009). These effects might also support fibroblast conversion into neural precursors and iSCs. Additionally, our approach included small molecule-based inhibition of TGF-β, BMP, and GSK3 signaling, a strategy known to direct differentiation of ESCs to neuroepithelial and/or neural crest fates (Chambers et al., 2009; Menendez et al., 2011).