Lee B.H. Shim J.Y. Moon H.C. Kim D.W. Kim, Ji won Yook J.S. Kim, Jinhyun Park H.Y. 2024-01-12T03:01:33Z 2024-01-12T03:01:33Z 2022-08-03 2022-07 0027-8424 https://pubs.kist.re.kr/handle/201004/76667 Memories are thought to be encoded in populations of neurons called memory trace or engram cells. However, little is known about the dynamics of these cells because of the difficulty in real-time monitoring of them over long periods of time in vivo. To overcome this limitation, we present a genetically encoded RNA indicator (GERI) mouse for intravital chronic imaging of endogenous Arc messenger RNA (mRNA)―a popular marker for memory trace cells. We used our GERI to identify Arc-positive neurons in real time without the delay associated with reporter protein expression in conventional approaches. We found that the Arc-positive neuronal populations rapidly turned over within 2 d in the hippocampal CA1 region, whereas ∼4% of neurons in the retrosplenial cortex consistently expressed Arc following contextual fear conditioning and repeated memory retrievals. Dual imaging of GERI and a calcium indicator in CA1 of mice navigating a virtual reality environment revealed that only the population of neurons expressing Arc during both encoding and retrieval exhibited relatively high calcium activity in a context-specific manner. This in vivo RNA-imaging approach opens the possibility of unraveling the dynamics of the neuronal population underlying various learning and memory processes. English National Academy of Sciences Real-time visualization of mRNA synthesis during memory formation in live mice Article 10.1073/pnas.2117076119 1 Proceedings of the National Academy of Sciences of the United States of America, v.119, no.27 Proceedings of the National Academy of Sciences of the United States of America 119 27 Y scie scopus 000838706400014 2-s2.0-85133835584 Multidisciplinary Sciences Science & Technology - Other Topics IN-VIVO GENE-EXPRESSION CELLULAR RESOLUTION PLACE CELLS EXPERIENCE DYNAMICS ARC CONSOLIDATION REACTIVATION ENSEMBLES Arc mRNA vivo imaging virtual reality memory trace engram