Cord Blood-derived neurons by ectopic expression of SOX2 and c-MYC

Abstract 2350

The finding that the epigenome of differentiated cells can be reset to a pluripotent state indicates that any somatic cell may potentially change or reverse its already established developmental identity through the delivery of appropriate instructive signals. Here we show the possibility of generating mature and functional neurons from Cord Blood (CB) cells without reprogramming into a pluripotent state. In particular, we demonstrate that the ectopic expression of two transcription factors (SOX2, c-MYC) as well as only one factor (SOX2) allows the generation of proliferating neural progenitor cells starting from CB CD133+ cells. Given its important role in neural stem cell activity, we first tested if only SOX2 was sufficient to induce the conversion of CB cells into neural progenitor cells. Three weeks after retrovirus infection, we observed the formation of a few colonies showing an iPS morphology, although they were negative for pluripotency markers (OCT4, NANOG, SSEA4). However, these colonies homogenously expressed multiple neural markers (TJU1, GFAP, MAP2, PAX6, NF) and we called them CB-inducible neural cells (CB-iNCs). Since, it is known that c-MYC has a role in controlling self-renewal and proliferation of neural progenitor cells, we therefore tested the neuron-inducing activity of SOX2 in combination with c-MYC. The data showed that the presence of c-MYC increased the efficiency 20 fold. In addition, we have demonstrated that CB-iNCs were able to differentiate into functional mature neurons in vitro and in vivo. The expression of the mature synaptic marker, synapsin, and both excitatory (VGLUT-1) as well as inhibitory markers (GABA), indicated that CB-derived neurons had the protein machinery necessary to fire action potentials. To investigate if CB-derived neurons had functional membrane properties similar to neurons, we performed patch-clamp recording and calcium transient assays. The results confirmed that CB-derived neurons could form functional synapses and generate action potentials. Finally, an in vivo assay, where CB-derived neurons were injected into dentate girus of mice hippocampus, demonstrated that these cells were able to engraft, differentiate as well as extend processes along the corpus callosum, one month after transplantation. Next we compared the global gene expression analysis of CB CD133+ cells, CB-iNCs and CB-derived mature neurons. The results indicated that CB-derived neurons have a neural transcription profile similar to neurons derived from human ES. In addition, to gain further insight into the role of SOX2 during the conversion process, we investigated whether genes up-regulated in CB-iNCs, which are known to have potential SOX2 binding sites were also bound by SOX2 in our CB-iNCs. Using Chromatin immunoprecipitation (ChIP) we found evidence that SOX2 was bound to NEUROD1, DCX, NAV2, MASH1 and CHD7 genes. All these data suggest that the ectopic expression of SOX2 and c-MYC as well as only SOX2 can rapidly convert CB cells into function neurons. The possibility to generate functional neurons starting from CB cells, in an efficient and easy way, could offer a novel and powerful system for studying human cellular identity and plasticity.