Project description:Extinction learning refers to the phenomenon that a previously learned response to an environmental stimulus, for example the expression of an aversive behavior upon exposure to a specific context, is reduced when the stimulus is repeatedly presented in the absence of a previously paired aversive event. Extinction of fear memories has been implicated with the treatment of anxiety disease but the molecular processes that underlie fear extinctionare only beginning to emerge. Here we show that fear extinction initiates up-regulation of hippocampal insulin-growth factor 2 (Igf2) and down-regulation of insulin-growth factor binding protein 7 (Igfbp7). In line with this observation we demonstrate that IGF2 facilitates fear extinction, while IGFBP7 impairs fear extinction in an IGF2-dependent manner. Furthermore, we identify one cellular substrate of altered IGF2-signaling during fear extinction. To this end we show that fear extinction-induced IGF2/IGFBP7-signaling promotes the survival of 17-19 day-old newborn hippocampal neurons. In conclusion, our data suggests that therapeutic strategies that enhance IGF2-signaling and adult neurogenesis might be suitable to treat disease linked to excessive fear memory. We employed mice to investigate fear extinction in the hippocampus-dependent contextual fear conditioning paradigm. To this end, male C57BL/6J mice were exposed to the fear conditioning box (context) followed by an electric foot-shock which elicits the acquisition of conditioned contextual fear. For extinction training animals were repeatedly reexposed to the conditioned context on consecutive days (24h interval) without receiving the footshockagain (extinction trial, E). This procedure eventually results in the decline of the aversive freezing behavior. Mice that were exposed to the conditioning context without receiving fear conditioning training served as control groups. To gain a better understanding of the molecular processes underlying fear extinction we performed a genome-wide analysis of the hippocampal transcriptome during fear extinction. In the employed paradigm fear extinction is a gradual process. To capture the longitudinal course of fear extinction we decided to perform hippocampal microarray analysis at two time points: (1) After the first extinction trial (E1) when animals display high levels of aversive freezing behavior and (2) at the extinction trial on which the freezing behavior was significantly reduced when compared to E1. This extinction trial, in the case of this experiment E5, we termed “extinction trial low freezing” (ELF). Mice that were exposed to the conditioning context without receiving fear conditioning training served as control groups (3). For all three groups we hybridized 5 samples (biological replicates).
Project description:LncRNAs are involved in critical processes for cell homeostasis and function. However, it remains largely unknown whether and how the transcriptional regulation of long noncoding RNAs results in activity-dependent changes at the synapse and facilitate formation of long-term memories. Here, we report the identification of a novel lncRNA, SLAMR, that becomes enriched in CA1- but not in CA3-hippocampal neurons upon contextual fear conditioning. SLAMR is transported to dendrites via the molecular motor KIF5C and recruited to the synapse in response to stimulation. Loss of function of SLAMR reduced dendritic complexity and impaired activity-dependent changes in spine structural plasticity. Interestingly, the gain of function of SLAMR enhanced dendritic complexity, and spine density through enhanced translation. Analyses of the SLAMR interactome revealed its association with CaMKIIa protein through a 220-nucleotide element and its modulation of CaMKIIa activity. Furthermore, loss-of-function of SLAMR in CA1 selectively impairs consolidation but neither acquisition, recall, nor extinction of fear memory and spatial memory. Together, these results establish a new mechanism for activity dependent changes at the synapse and consolidation of contextual fear memory.
Project description:Quantitative proteomic analysis was used to identify the proteins associated with a formation of fear memory in mice. The proteins from the hippocampal region were isolated from three groups of trained aminals representing aquisition, consolidation and retrieval of a contextual fear conditioning. The samples were digested by trypsin, analyzed by LC-MSMS followed by protein identification and label-free quantitation using MaxQuant 1.3.0.5. Each group consisted of three individuals and each sample was processed in two technical replicates.
Project description:The goal of our study was to assess whether the experience can regulate specific lncRNAs within the hippocampus and their role in associative memory. To address this, we carried out unbiased analyses of gene expression in CA1-hippocampal neurons to identify lncRNA changes induced by contextual fear conditioning (CFC).
Project description:Extinction learning refers to the phenomenon that a previously learned response to an environmental stimulus, for example the expression of an aversive behavior upon exposure to a specific context, is reduced when the stimulus is repeatedly presented in the absence of a previously paired aversive event. Extinction of fear memories has been implicated with the treatment of anxiety disease but the molecular processes that underlie fear extinctionare only beginning to emerge. Here we show that fear extinction initiates up-regulation of hippocampal insulin-growth factor 2 (Igf2) and down-regulation of insulin-growth factor binding protein 7 (Igfbp7). In line with this observation we demonstrate that IGF2 facilitates fear extinction, while IGFBP7 impairs fear extinction in an IGF2-dependent manner. Furthermore, we identify one cellular substrate of altered IGF2-signaling during fear extinction. To this end we show that fear extinction-induced IGF2/IGFBP7-signaling promotes the survival of 17-19 day-old newborn hippocampal neurons. In conclusion, our data suggests that therapeutic strategies that enhance IGF2-signaling and adult neurogenesis might be suitable to treat disease linked to excessive fear memory.
Project description:Among all voltage-gated calcium channels, the T-type Ca2+ channels encoded by the Cav3 genes are highly expressed in the hippocampus, which is associated with contextual, temporal and spatial learning and memory. However, the specific involvement of the Cav3.2 T-type Ca2+ channel in these hippocampus-dependent types of learning and memory remains unclear. To investigate the functional role of the 1H channel in learning and memory, we subjected Cav3.2 homozygous, heterozygous knockout and their wild-type littermates to hippocampus-dependent behavioral tasks, including trace fear conditioning (TFC), the Morris water-maze and passive avoidance. The Cav3.2-/- mice performed normally in the Morris water-maze and auditory trace fear conditioning tasks but were impaired in the context-cued trace fear conditioning, step-down and step-through passive avoidance tasks. Furthermore, long-term potentiation (LTP) could be induced for 180 minutes in hippocampal slices of WTs and Cav3.2+/- mice, whereas LTP persisted for only 120 minutes in Cav3.2-/- mice. To determine whether the hippocampal formation is responsible for the impaired behavioral phenotypes , we next performed experiments locally knock down function of the Cav3.2 T-type Ca2+ channel in the hippocampus. Wild-type mice infused with mibefradil exhibited similar behaviors as homozygous knockouts. Finally, microarray analyses indicated that Cav3.2-/- and WT mice presented distinct hippocampal transcriptome profiles. Taken together, our results demonstrate that retrieval of context-associated memory is dependent on the Cav3.2 T-type Ca2+ channel. After WT and Cav3.2 KO mice retrieval of context-associated memory, three right hippocampi of each group were dissected, pooled together and homogenized. The products of experimental and naive groups were used to acquire expression profiles of a total of 29,922 unique genes. Two replicates per group.
Project description:Among all voltage-gated calcium channels, the T-type Ca2+ channels encoded by the Cav3 genes are highly expressed in the hippocampus, which is associated with contextual, temporal and spatial learning and memory. However, the specific involvement of the Cav3.2 T-type Ca2+ channel in these hippocampus-dependent types of learning and memory remains unclear. To investigate the functional role of the 1H channel in learning and memory, we subjected Cav3.2 homozygous, heterozygous knockout and their wild-type littermates to hippocampus-dependent behavioral tasks, including trace fear conditioning (TFC), the Morris water-maze and passive avoidance. The Cav3.2-/- mice performed normally in the Morris water-maze and auditory trace fear conditioning tasks but were impaired in the context-cued trace fear conditioning, step-down and step-through passive avoidance tasks. Furthermore, long-term potentiation (LTP) could be induced for 180 minutes in hippocampal slices of WTs and Cav3.2+/- mice, whereas LTP persisted for only 120 minutes in Cav3.2-/- mice. To determine whether the hippocampal formation is responsible for the impaired behavioral phenotypes , we next performed experiments locally knock down function of the Cav3.2 T-type Ca2+ channel in the hippocampus. Wild-type mice infused with mibefradil exhibited similar behaviors as homozygous knockouts. Finally, microarray analyses indicated that Cav3.2-/- and WT mice presented distinct hippocampal transcriptome profiles. Taken together, our results demonstrate that retrieval of context-associated memory is dependent on the Cav3.2 T-type Ca2+ channel. After WT and Cav3.2 KO mice retrieval of context-associated memory, three left hippocampi of each group were dissected, pooled together and homogenized. The products of experimental and naive groups were used to acquire expression profiles of a total of 29,922 unique genes. Two replicates per group.