A loss-of-function study of CRTC1 in hippocampal neurons at basal state and during long-term synaptic plasticity

• Main Author: Lim, Agnes Fang Yi
• Other Authors: Ch’ng Toh Hean
• Format: Theses and Dissertations
• Language: English
• Published: 2019
• Subjects: Science::Biological sciences
• Online Access: https://hdl.handle.net/10356/85237; http://hdl.handle.net/10220/49191
• Institution: Nanyang Technological University

Encoding of long-term memory in neurons requires gene expression and protein synthesis. CREB, a well-characterised stimulus-induced transcription factor, is implicated in gene transcription supporting long-term plasticity. Several studies showed that CRTC1 is an important co-activator for CREB activity. Although CRTC1 is most abundantly expressed in the brain, its function during memory formation remains poorly understood. Studies have revealed that CRTC1 could modulate long-term plasticity in the hippocampus, but extensive use of a conditional deletion strategy has never been performed. Hence, the overall aim of this project is to rigorously examine the impact of nuclear CRTC1 translocation and transcription in regulating long-term memories. We investigated the role of CRTC1 in hippocampal neurons by knocking out CRTC1 protein expression using the lentiCRISPR/Cas9 system that we established. Our results indicate that basal loss of CRTC1 reduced the number of inhibitory synaptic protein expression in hippocampal neurons, therefore leading to enhanced action potential firing and reduced mIPSCs. We report that the loss of excitatory synaptic protein expression only occurred in bicuculline-stimulated cultures. We also show that chemically-induced long-term potentiation and depression triggered CRTC1 nuclear accumulation in hippocampal neurons. During long-term plasticity, loss of CRTC1 perturbed the overall transcription of several CREB-mediated immediate early genes. In particular, the expression of an important regulator of excitatory-inhibitory balance in the hippocampal neurons, Npas4, is reduced. Hence, we speculate that CRTC1 is crucial for the regulation of multiple CREB-mediated target gene transcription, including Npas4 and that loss of Npas4 expression perhaps contributes to the reduction in inhibition.