Gene expression profiling of shRNA transduced rat hippocampal neurons

Sirtuin 6 (SIRT6), a member of the sirtuin family, acts as nicotinamide adenine dinucleotide-dependent protein deacetylase, mono-adenosine diphosphate-ribosyltransferase, and fatty acid deacylase and plays critical roles in inflammation, aging, glycolysis, and DNA repair. Accumulating evidence has suggested that SIRT6 is involved in brain functions such as neuronal differentiation, neurogenesis, and learning and memory. However, the precise molecular roles of SIRT6 during neuronal circuit formation are not well understood. In this study, we attemped to elucidate the molecular roles of SIRT6 on neurite development using a primary culture of hippocampal neurons. We observed that SIRT6 was abundantly localized in the nucleus, and its expression was markedly increased during neurite outgrowth and synaptogenesis. Using shRNA-mediated SIRT6 knockdown, we showed that the dendritic length and number of dendrite branches were significantly reduced in SIRT6 knockdown neurons. Microarray and subsequent gene ontology analysis revealed that reducing SIRT6 caused the downregulation of immediate early genes (IEGs) and alteration of several biological processes including MAPK (ERK1/2) signaling. We found that nuclear accumulation of phosphorylated ERK1/2 was significantly reduced in SIRT6 knockdown neurons. Overexpression of SIRT6 promoted dendritic length and branching, but the mutants lacking deacetylase activity had no significant effect on the dendritic morphology. Collectively, the presented findings reveal a role of SIRT6 in dendrite morphogenesis and suggest that SIRT6 may act as an important regulator of the ERK1/2 signaling pathway that mediates IEG expression, which leads to dendritic development. To understand the molecular function of SIRT6 in neuronal morphogenesis, we performed microarray analysis using total RNA isolated from shRNA transduced rat hippocampal neurons.