Identification of CAMTA1 target genes in the adult mouse hippocampus. Mus musculus

The formation of long-term memory requires signaling from the synapse to the nucleus to mediate neuronal activity-dependent gene transcription. Synapse-to-nucleus communication is initiated by influx of calcium ions through synaptic NMDA receptors and/or L-type voltage-gated calcium channels and involves the activation of transcription factors by calcium/calmodulin signaling in the nucleus. Recent studies have drawn attention to a new family of transcriptional regulators, the so-called calmodulin-binding transcription activator (CAMTA) proteins. CAMTAs are expressed at particularly high levels in the mouse and human brain, and we reasoned that, as calmodulin-binding transcription factors, CAMTAs may regulate the formation of long-term memory by coupling synaptic activity and calcium/calmodulin signaling to memory-related transcriptional responses. This hypothesis is supported by genetic studies that reported a correlation between CAMTA gene polymorphisms or mutations and cognitive capability in humans. Here, we show that acute knock-down of CAMTA1, but not CAMTA2, in the hippocampus of adult mice results in impaired performance in two memory tests, contextual fear conditioning and object-place recognition test. Short-term memory and neuronal morphology were not affected by CAMTA knock-down. Gene expression profiling in the hippocampus of control and CAMTA knock-down mice revealed a number of putative CAMTA1 target genes related to synaptic transmission and neuronal excitability. Patch clamp recordings in organotypic hippocampal slice cultures provided further evidence for CAMTA1-dependent changes in electrophysiological properties. In summary, our study provides experimental evidence that confirms previous human genetic studies and establishes CAMTA1 as a regulator of long-term memory formation. Overall design: We compared the mRNA expression profile of three groups, i.e. mice infected with a recombinant adeno-associated virus (rAAV) expressing a non-targeting control shRNA, mice infected with a rAAV expressing Camta1 targeting shRNA sequence A, and mice infected with a rAAV expressing Camta1 targeting shRNA sequence B. Three animals were used per group.