Activity-dependent regulation of inhibitory synapse development by Npas4

Abstract

Neuronal activity regulates the development and maturation of excitatory and inhibitory synapses in the mammalian brain. Several recent studies have identified signalling networks within neurons that control excitatory synapse development. However, less is known about the molecular mechanisms that regulate the activity-dependent development of GABA (γ-aminobutyric acid)-releasing inhibitory synapses. Here we report the identification of a transcription factor, Npas4, that plays a role in the development of inhibitory synapses by regulating the expression of activity-dependent genes, which in turn control the number of GABA-releasing synapses that form on excitatory neurons. These findings demonstrate that the activity-dependent gene program regulates inhibitory synapse development, and suggest a new role for this program in controlling the homeostatic balance between synaptic excitation and inhibition.

Neuronal Per Arnt Sim (PAS) Domain Protein 4 (NPAS4) Regulates Neurite Outgrowth and Phosphorylation of Synapsin I

“…To measure neurite outgrowth, hippocampal neurons were dissociated and prepared from E16 to E17 mouse embryos of Npas4 knock-out (KO) or wild-type (WT) littermates as described above. Npas4 KO mice were kindly donated by Dr. Greenberg (13). The longest Tau-positive axonal length was measured at DIV 3.…”

“…Chromatin Immunoprecipitation Assay (ChIP Assay)-Neuro2a cells (3.9 ϫ 10 7 cells, 10 cm dish) were seeded, and 96 h later the medium was replaced with DM, and the cells were cultured for 48 h. Primary cultured cortical neurons (4.0 ϫ 10 7 cells, 10-cm dish) on DIV 4 were treated with tetrodotoxin and AP5 (an N-methyl-D-aspartate receptor antagonist) followed by KCl according to the protocol of Lin et al (13). A ChIP assay was performed with a Simple Chip Enzymatic Chromatin IP kit (Cell Signaling Technology) following the manufacturer's manual.…”

“…An Npas4 promoter was used as a positive control (13). The ChIP assay revealed that NPAS4 binds to promoter regions of Cdk5 and NeuN in DM-treated Neuro2a cells (Fig.…”

“…Npas3 has been identified as a candidate gene associated with schizophrenia, learning disabilities, and bipolar disorder (5,10), and it is known to play a role in hippocampal neurogenesis (1,11). NPAS4 is a neuron-specific transcription factor (12), and the Npas4 expression level in the hippocampus is regulated by cerebral ischemic insults, the AMPA receptor agonist and kainic acid (13)(14)(15). Lin et al (13) have reported that NPAS4 regulates the development of GABAergic inhibitory synapses in an activity-dependent manner and suggested its homeostatic role in the balance between excitatory and inhibitory neuronal activities in the brain.…”

MeCP2: Making sense of missense in Rett syndrome

“…T308A mice showed normal levels of depolarization-induced expression of most immediate-early genes (Arc, Fos, Nptx2 and Adcyap1). However, mRNA levels of two genes, Npas4, which plays an important role in inhibitory synaptic maturation and plasticity [8,9], and Bdnf, which is activated by Npas4, were reduced in T308A knock-in neurons compared to wild-type controls. Prolonged dark-rearing of adult mice followed by 6 h of light exposure also demonstrated attenuation of Npas4 and Bdnf induction in visual cortex.…”