TGF-beta and Notch pathway in cell fate decision of adult neural stem cells from the subventricular zone.

PATRICIA MATHIEU; ANA M. ADAMO

Congreso; 44th Annual Meeting of the Society for Neuroscience; 2014

Adult neural stem cells (aNSC) are capable to differentiate into neurons, astrocytes and oligodendrocytes throughout life. Notch and transforming growth factor beta 1 (TGF-beta) signaling pathways play critical roles in controlling cell fate. Previously it was demonstrated that TGF-beta is pro-neurogenic on hippocampal aNSC and it was reported that might interact with Notch pathway in different cellular types. Therefore the aim of our work is to study the effect of this cytokine on the generation of specific cell types from aNSC of the subventricular zone (SVZ) and its interaction with the Notch pathway. In order to study TGF-beta and Notch pathway interaction in neuronal differentiation of aNSC we cultured the cells obtained from the SVZ of Wistar adult rats at 3% oxygen tension in cell culture media containing 2% B27 supplement and 20ng/ml basic fibroblast growth factor (FGF-2) to support neuronal differentiation. After 48 h of plating, cells were fixed and an immunocytochemistry was performed. Most of cells in the aNSC cultures were Nestin and glial fibrillary acidic protein (GFAP) positive whereas a low percentage of cells expressed neuronal markers as beta III tubulin (Tuj1) or microtubule-associated protein 2 (MAP2). The treatment of the aNSC with TGF-beta during four days significantly increased the percentage of Tuj1 positive cells demonstrating the pro-neurogenic effect of this cytokine on neural progenitor cells of the adult SVZ. Besides, this pro-neurogenic effect was not related to cell proliferation. Shortly after TGF-beta exposure of aNSC cultures there was an increase in the expression of Notch ligand Jagged1 and a target gene of Notch pathway activation, Hes1. The expression of Ascl1, a pro-neurogenic gene, was not modified 6 h after TGF-beta exposure, and there was a slight increase after 24 h of incubation with the cytokine. Moreover the presence of a gamma-secretase inhibitor blocks the increase in Hes1 expression and the pro-neurogenic effect of TGF-beta. These results suggest that the effect of TGF-beta in cell fate decision could be in part due a change in Notch pathway activation. Currently we are exploring the effect of TGF-beta in glial differentiation of aNSC from SVZ working at atmospheric oxygen tension and with the addition of epidermal growth factor in order to enhance glial differentiation.