Genome-wide translational profiling of amygdala Crh-expressing neurons reveals role for CREB in fear extinction learning

Abstract

Fear and extinction learning are adaptive processes caused by molecular changes in specific neural circuits. Neurons expressing the corticotropin-releasing hormone gene (Crh) in central amygdala (CeA) are implicated in threat regulation, yet little is known of cell type-specific gene pathways mediating adaptive learning. We translationally profiled the transcriptome of CeA Crh-expressing cells (Crh neurons) after fear conditioning or extinction in mice using translating ribosome affinity purification (TRAP) and RNAseq. Differential gene expression and co-expression network analyses identified diverse networks activated or inhibited by fear vs extinction. Upstream regulator analysis demonstrated that extinction associates with reduced CREB expression, and viral vector-induced increased CREB expression in Crh neurons increased fear expression and inhibited extinction. These findings suggest that CREB, within CeA Crh neurons, may function as a molecular switch that regulates expression of fear and its extinction. Cell-type specific translational analyses may suggest targets useful for understanding and treating stress-related psychiatric illness.

Optogenetic Stimulation of Prelimbic Pyramidal Neurons Maintains Fear Memories and Modulates Amygdala Pyramidal Neuron Transcriptome

“…Finally, we observed that fear conditioning per se (in the presence of an adaptive extinction), without optogenetic stimulation, was not greatly associated with gene expression in amygdala pyramidal neurons ( Figure 6 D,E, Table 4 ), in line with PCA highlighting poor segregation between SHAM FEAR vs. SHAM NOT FEAR groups. This result is in line with those reported by McCullough and colleagues [ 41 ] who described a weak separation between the transcriptomes of fear- and not fear-conditioned animals. The authors discussed their findings as result of stress-induced translational changes due to the handling of animals and CS exposure.…”

“…The present findings indicate that impaired extinction is featured by specific changes of transcriptome that validate previous findings [ 41 ], provide targets for future translational research into cell type-specific control of fear extinction, and emphasize the key role of pyramidal neurons belonging to fear matrix. This type of comprehensive cell-type specific analysis may produce an important array of targets potentially useful for diagnosis, treatment, and prevention of fear-related disorders.…”

“…Among these, 3 DEGs (i.e., Brinp1 , associated to Fear response and Memory; Bcl2 , associated to Fear response; Agt , associated to Learning) were part of the most impacted genes (top twenty DEGs), and resulted strongly down regulated in OPTO FEAR group. Several genes previously associated with fear extinction in the literature [ 41 , 49 , 50 , 51 , 52 , 53 , 54 ] were present in OPTO FEAR group, as down regulated ( Apoe , Cacna1c , Creb1 , Homer1 ) or up regulated ( App , Arc ). Although not always the afore-mentioned genes have been associated specifically to amygdala activity, those down regulated have been positively associated with extinction, while those up regulated have been positively associated with fear memory retention.…”

“…Cell-type-specific transcriptome analysis represents cutting-edge tool to reveal targets useful for understanding and treating fear-related disorders. Differential gene expression and co-expression network analyses identified diverse networks activated or inhibited by fear learning vs. extinction, and upstream regulator analysis and viral vector-manipulations demonstrated that fear extinction is associated with reduced cAMP/Ca 2+ responsive element binding (CREB) expression [ 41 ].…”

“…In parallel, the top twenty KEGG terms were associated with processes related to several neurodegenerative diseases, metabolic pathways, production of lipids and proteins, and thyroid hormone and neurotrophin signaling. Remarkably, fear-associated enrichments have been related with dendritic and post-synaptic processes, while extinction-associated enrichments have been related with cellular metabolism and proliferation [ 41 ].…”