Crtc1 Activates a Transcriptional Program Deregulated at Early Alzheimer's Disease-Related Stages

Abstract

Cognitive decline is associated with gene expression changes in the brain, but the transcriptional mechanisms underlying memory impairments in cognitive disorders, such as Alzheimer's disease (AD), are largely unknown. Here, we aimed to elucidate relevant mechanisms responsible for transcriptional changes underlying early memory loss in AD by examining pathological, behavioral, and transcriptomic changes in control and mutant ␤-amyloid precursor protein (APP Sw,Ind ) transgenic mice during aging. Genome-wide transcriptome analysis using mouse microarrays revealed deregulation of a gene network related with neurotransmission, synaptic plasticity, and learning/memory in the hippocampus of APP Sw,Ind miceafterspatialmemorytraining.Specifically,APP Sw,Ind miceshowchangesonacAMP-responsiveelementbindingprotein(CREB)-regulated transcriptional program dependent on the CREB-regulated transcription coactivator-1 (Crtc1). Interestingly, synaptic activity and spatial memory induces Crtc1 dephosphorylation (Ser151), nuclear translocation, and Crtc1-dependent transcription in the hippocampus, and these events are impaired in APP Sw,Ind mice at early pathological and cognitive decline stages. CRTC1-dependent genes and CRTC1 levels are reduced in human hippocampus at intermediate Braak III/IV pathological stages. Importantly, adeno-associated viral-mediated Crtc1 overexpression in the hippocampus efficiently reverses A␤-induced spatial learning and memory deficits by restoring a specific subset of Crtc1 target genes. Our results reveal a critical role of Crtc1-dependent transcription on spatial memory formation and provide the first evidence that targeting brain transcriptome reverses memory loss in AD.

[P3–175]: Crtc1 Function During Memory Encoding Is Disrupted in Neurodegeneration

“…A role of CRTC1 in associative memory is further supported by previous findings indicating that spatial memory training induces CRTC1 nuclear translocation in the hippocampus (35), and that CRTC1 overexpression in the dorsal hippocampus enhances contextual fear memory (30,31) (Figure 6C). In agreement, contextual learning induces CREB-mediated transcription in CA1/CA3 hippocampus, whereas cued fear-conditioning activates CREB in the amygdala (23).…”

“…Do CRTC1-dependent transcription changes contribute to associative memory deficits in neurodegeneration? CRTC1-dependent transcriptional deficits were recently associated with early pathological and memory changes in APP mice and a rat AD model that do not develop neurodegeneration (35,68). Pharmacological activation of CREB signaling has been useful to reverse memory and synaptic deficits in AD mice (69)(70)(71).…”

“…Adeno-associated virus (AAV2/10) from rhesus macaque (AAVrh.10) containing Crtc1-myc under the -actin promoter was generated by subcloning pcDNA3-Crtc1-myc (27) into pVAX1 (Thermo Fisher Scientific, USA) and pGV-IRES2-GFP vectors as described (35). For viral injections, 4-4.5 month-old mice (n= 6-8 mice/group) were anesthetized with isofluorane and injected bilaterally into the dorsal hippocampus with AAV-GFP or AAV-Crtc1-myc (3 μl; 5.1x10 11 gc/ml; 0.5 μl/min).…”

“…Fragmented chromatin (200-500 bp) was analyzed using the High Sensitivity DNA Kit (Agilent Technologies). Chromatin immunoprecipitation (2.5 μg) was performed overnight in diluted ChIP buffer (0.1% SDS, 1,1% Triton X-100) with or without rabbit anti-CRTC1 and CREB antibodies (Cell Signaling) (35). Input and immunoprecipitated DNA were decrosslinked and amplified by real-time qPCR using specific primers, and the fold enrichment was calculated over an irrelevant region.…”

“…Previous studies have shown that CRTC1 activation is mediated by activity-dependent CRTC1 dephosphorylation and nuclear translocation (31,35,41). We first investigated the regulation of (50 fold) and Nr4a3 (4 fold) (P< 0.001, one-way ANOVA; Figure 2B).…”