Microarray Analyses Support a Role for Nurr1 in Resistance to Oxidative Stress and Neuronal Differentiation in Neural Stem Cells

Abstract

Nurr1 is an orphan nuclear receptor required for the development of midbrain dopaminergic neurons. To better understand the molecular consequences of Nurr1 expression, we compared the transcriptomes of two independent control and Nurr1-expressing NSC lines using Affymetrix cDNA microarrays. These data reveal the regulation of genes involved in promoting cell survival (trophic/growth factors and stress response genes) and in preventing cell death (decreased caspase-3 and caspase-11 expression). We found that conditioned medium from Nurr1-expressing NSC lines enhanced the survival of midbrain dopaminergic neurons in primary cultures and that Nurr1-expressing NSC lines themselves were more resistant to oxidative stress. These findings are accompanied by a dynamic pattern of gene regulation that is consistent with a role for Nurr1 in promoting both the acquisition of brain-region-specific identity (Engrailed-1) and neuronal differentiation (tubulin beta III). Interestingly, our gene expression profiles suggested that tenascin-C was regulated by Nurr1 in developing dopaminergic neurons. This was further confirmed in vitro and in Nurr1 knockout mice where low levels of tenascin-C mRNA were observed. Analysis of tenascin-C-null mice revealed an increase in the number of Nurr1(+) cells that become tyrosine hydroxylase-positive (TH(+)) dopaminergic neurons at embryonic day 11.5, suggesting that tenascin-C normally delays the acquisition of TH by Nurr1(+) precursors. Thus, our results confirm the presence of both secreted and cell-intrinsic survival signals modulated by Nurr1 and suggest that Nurr1 is a key regulator of both survival and dopaminergic differentiation.