In the adult mammalian brain, production of new neurons persists in two neural stem/progenitor cell (NSPC) niches that are located in the subventricular zone (SVZ) of the lateral ventricles and in the subgranular zone of the hippocampus, respectively. Adult neurogenesis decreases with ageing, and this may significantly contribute to age-associated decline in brain function and to the increased frequency of neurological conditions in elderly patients. Despite the potential importance of these findings for human health, the underlying molecular causes of the decline in neurogenesis upon ageing are still unknown. To gain insight into the intrinsic molecular changes taking place in NSPCs during ageing, we recently performed genome-wide analyses of the transcriptional profiles of NSPCs derived from the SVZ of adult (3 months old) and aged (18 months old) mice. This analysis led to the identification of a few hundred loci showing transcriptional changes between adult and aged NSPCs. Among them, we have focused on Dbx2, a homeobox gene significantly upregulated in aged NSPCs in comparison with adult NSPCs. We found that overexpression of Dbx2 in adult NSPCs in vitro recapitulates some of the phenotypic changes associated with NSPC ageing, such as decreased NSPC ability to grow in culture and altered expression of genes implicated in NSPC self-renewal and differentiation. The goal of the proposed project is to study the effects of the loss-of-function of this gene in aged NSPCs and, in particular, to address whether Dbx2 inactivation can rescue the decreased growth capacity and the altered transcriptional profiles of aged NSPCs. Dbx2 function will be knocked down in aged NSPCs in vitro by transfecting them with plasmids expressing short-hairpin RNAs. The effects of this manipulation will be characterised through a variety of technical approaches including cell proliferation and cell viability assays and molecular markers analyses by real-time PCR and immunocytochemistry.
For several decades, mammalian brain cell proliferation and neurogenesis were thought to be restricted to embryonic and early postnatal life, with later brain function relying on the neurons produced during an early developmental window. A different model emerged twenty years ago, however, with the discovery of two adult stem cell niches in the SVZ of the lateral ventricles and the SGZ of the hippocampus, where neural NSPCs persist and generate new neurons during adult life.
Adult neurogenesis decreases with ageing, and this may significantly contribute to age-associated decline in brain function and to the increased frequency of neurological conditions in elderly patients. Despite the potential importance of these findings for human health, the underlying molecular causes of the decline in neurogenesis upon ageing are still largely unknown. Because NSPC self-renewal and lineage differentiation are characteristically altered during ageing, this raises the possibility that age-associate changes in the transcriptional regulation of NSPCs may have an important and unexplored role in neurogenic decline during ageing.
This study will provide important insight into the molecular differences between adult and aged NSPCs, and will identify altered pathways and regulators that may underlie the changes in self-renewal and neurogenic capacity that characterise the ageing brain. Importantly, the NSPC culture system employed for this project provides a tractable model for future studies to investigate the cellular and functional changes occurring in aged NSPCs based on the knowledge of their transcriptional signatures and the identification of key transcriptional regulators associated with NSPC ageing.