NPAS3 Regulates Transcription and Expression of VGF: Implications for Neurogenesis and Psychiatric Disorders

Abstract

Neuronal PAS domain protein 3 (NPAS3) and VGF (VGF Nerve Growth Factor (NGF) Inducible) are important for neurogenesis and psychiatric disorders. Previously, we have demonstrated that NPAS3 regulates VGF at the transcriptional level. In this study, VGF (non-acronymic) was found regulated by NPAS3 in neuronal stem cells. However, the underlying mechanism of this regulation remains unclear. The aim of this study was to explore the correlation of NPAS3 and VGF, and their roles in neural cell proliferation, in the context of psychiatric illnesses. First, we focused on the structure of NPAS3, to identify the functional domain of NPAS3. Truncated NPAS3 lacking transactivation domain was also found to activate VGF, which suggested that not only transactivation domain but other structural motifs were also involved in the regulation. Second, Mutated enhancer box (E-box) of VGF promoter showed a significant response to this basic helix-loop-helix (bHLH) transcription factor, which suggested an indirect regulatory mechanism for controlling VGF expression by NPAS3. κB site within VGF promoter was identified for VGF activation induced by NPAS3, apart from direct binding to E-box. Furthermore, ectopically expressed NPAS3 in PC12 cells produced parallel responses for nuclear factor kappa-light-chain-enhancer of activated B cells [NF-κB (P65)] expression, which specifies that NPAS3 regulates VGF through the NF-κB signaling pathway. Over-expression of NPAS3 also enhances the cell proliferation, which can be blocked by knockdown of VGF. Finally, NPAS3 was found to influence proliferation of neural cells through VGF. Therefore, downstream signaling pathways that are responsible for NPAS3-VGF induced proliferation via glutamate receptors were explored. Combining this work and published literature, a potential network composed by NPAS3, NF-κB, Brain-Derived Neurotrophic Factor (BDNF), NGF and VGF, was proposed. This network collectively detailed how NPAS3 connects with VGF and intersected neural cell proliferation, synaptic activity and psychiatric disorders.

H3.3 Barcoding of Nucleus Accumbens Transcriptional Activity Identifies Novel Molecular Cascades Associated with Cocaine Self-administration in Mice

“…VGF, which curiously is not an acronym, codes for a peptide that shares similarities with the granin family of secreted proteins (Borges et al, 2013). The expression of VGF is upregulated by neurotrophins, including BDNF (Alder et al, 2003), and VGF increases hippocampal neurogenesis (Thakker-Varia et al, 2007;Yang et al, 2016) and synaptic plasticity (Alder et al, 2003). Moreover, VGF KO mice have impaired spatial and fear memory (Bozdagi et al, 2008;Lin et al, 2015).…”

Single-cell interactomes of the human brain reveal cell-type specific convergence of brain disorders

“…For example, we found that glutamate signaling genes (GRIN1, GRIN2A, and GRIN2B) and AMPA receptors (GRIA1 and GRIA2), are highly influential in the neuronal networks. For glial cells, we found that NPAS3, which plays a regulatory role in neurogenesis (Sha et al 2012;Yang et al 2016) , influences the networks of cell types with proliferative capacity (OPC and astrocyte). In microglia we found Hypoxia-Inducible Factor (HIF)-1A, a gene that responds to a decrease in cellular oxygen availability, and which has been shown to mediate microglial activation affecting neuron function (Lu et al 2006) .…”

Molecular analysis of NPAS3 functional domains and variants

“…Microarray studies in human cells identified hundreds of target genes differentially regulated by expression of NPAS3, however, which are direct targets was not assessed [ 25 ]. Of the genes identified in this study, VGF (non-acronymic) has been shown to be regulated by NPAS3 in a manner dependent on constructs proximal to the promoter region [ 25 , 26 ]. Neither physical association with the promoter region, nor the contribution of ARNT to this regulation were assessed.…”