Transcriptional profiling by RNA-seq in Dbx2-overexpressing cultures of adult neural progenitors

In selected tissutal niches of the adult mouse brain, such as the subventricular zone (SVZ) underlying the lateral ventricles, neurogenesis persists thanks to a population of quiescent neural stem cells, which can be activated (aNSCs) by extrinsic stimuli to initiate proliferation and generate a neurogenic lineage consisting of transit amplifying progenitors (TAPs), neuroblasts (NBs) and newborn neurons. This process is markedly reduced during aging, which might contribute to the cognitive decline of elderly subjects. Recent studies suggest that the aged niche environment may decrease the pool of proliferating neural/stem progenitor cells (NSPCs), and hence adult neurogenesis, by causing transcriptomic changes that favour NSC quiescence over activation. The transcription factors that mediate these changes, however, remain largely unclear. We previously found that the homeobox gene Dbx2 is upregulated in NSPCs of the aged mouse SVZ and can inhibit the growth of young adult NSPC cultures. Here, we show that Dbx2 expression is downregulated by Epidermal Growth Factor Receptor signalling, which promotes NSPC proliferation and decreases in the aged SVZ. By means of transgenic NSPC lines, we also show that Dbx2 inhibits NSPC proliferation by hindering the G1/S and the G2/M transition. Furthermore, we exploit RNA sequencing of transgenic NSPCs to elucidate the transcriptional networks modulated by Dbx2. Among the top hits, we report the downregulation of several gene categories implicated in cell cycle progression. Accordingly, we find that Dbx2 function is negatively correlated with the transcriptional signatures of proliferative NSPCs (aNSCs, TAPs and early NBs). Altogether, these results point to Dbx2 as a potential molecular node relaying the extracellular anti-neurogenic input of the aged niche to the NSPC transcriptome. Overall design: mRNA profiles of transgenic NSPC lines with constitutive expression of a Dbx2 transgene, eight biological replicates for each experimental group.