Multi‐omics analysis suggests enhanced epileptogenesis in the Cornu Ammonis 3 of the pilocarpine model of mesial temporal lobe epilepsy

Abstract

Mesial temporal lobe epilepsy (MTLE) is a chronic neurological disorder characterized by the occurrence of seizures, and histopathological abnormalities in the mesial temporal lobe structures, mainly hippocampal sclerosis (HS). We used a multi-omics approach to determine the profile of transcript and protein expression in the dorsal and ventral hippocampal dentate gyrus (DG) and Cornu Ammonis 3 (CA3) in an animal model of MTLE induced by pilocarpine. We performed label-free proteomics and RNAseq from laser-microdissected tissue isolated from pilocarpine-induced Wistar rats. We divided the DG and CA3 into dorsal and ventral areas and analyzed them separately. We performed a data integration analysis and evaluated enriched signaling pathways, as well as the integrated networks generated based on the gene ontology processes. Our results indicate differences in the transcriptomic and proteomic profiles among the DG and the CA3 subfields of the hippocampus. Moreover, our data suggest that epileptogenesis is enhanced in the CA3 region when compared to the DG, with most abnormalities in transcript and protein levels occurring in the CA3. Furthermore, our results show that the epileptogenesis in the pilocarpine model involves predominantly abnormal regulation of excitatory neuronal mechanisms mediated by N-methyl D-aspartate (NMDA) receptors, changes in the serotonin signaling, and neuronal activity controlled by calcium/calmodulin-dependent protein Amanda M. Canto and Alexandre H. B. Matos should be considered joint first author.

Neuroproteomics in Epilepsy: What Do We Know so Far?

“…By contrast, there was a downregulation in the WNT signaling pathway in the CA3. These findings also highlight the heterogeneity in the transcriptome and proteome of different hippocampal regions and areas (Canto et al, 2020).…”

“…In a very recent study performed by our group in 2020, we employed the pilocarpine model to broadly assess changes in the proteome and transcriptome of Wistar rats (Canto et al, 2020). We isolated different regions of the hippocampal formation, DG and CA3, as well as different areas (dorsal and ventral), using laser microdissection and determined their protein and transcriptional profiles-the transcriptomic study used next-generation sequencing, while the proteomic study used a label-free mass spectrometry approach.…”

“…These profiles displayed, in the hippocampus, enriched pathways commonly linked to the regulation of cell death (14-3-3 and HIPPO signaling), cellular plasticity (cytoskeletal dynamics and axonal guidance), and carbohydrate and amino acid metabolism (Keck et al, 2018). More recently, our group analyzed the proteome of the DG from perforant pathway-stimulated rats by LC-MS/MS; we identified different proteomic profiles for the DG layers (granular and molecular) and regions (ventral and dorsal; do Canto et al, 2020). In all layers and regions, there were two enriched pathways that are important for determining the molecular bases for epileptogenesis and the cellular changes observed: inflammation and energy metabolism.…”

“…In addition to these pathways and proteins, others were linked to specific DG layers and regions. Proteins such as PARK7 and connexin 31/gap junction were differentially regulation in the ventral portion of the DG, and RACK1 expressed opposite differential regulation in the dorsal and ventral part of the DG (do Canto et al, 2020).…”

Hippocampal CA3 Transcriptional Modules Associated with Granule Cell Alterations and Cognitive Impairment in Refractory Mesial Temporal Lobe Epilepsy Patients

“…Pathomorphological studies showed compromised neurogenesis and signi cant DG cell loss in RMTLE patients 10,11 and in vitro and animal model assays showed that the improper circuit control of DG-CA3 synapses leads to epilepsy, since DG acts as a "gate", protecting hippocampal circuits from overexcitation 12,13 . Multi-omics analyses performed in the pilocarpine rat model of MTLE suggested enhanced epileptogenesis in the CA3 region when compared to the DG, with most of the transcriptional and protein expression alterations occurring in CA3 14 . Additionally, the integrative study of CA3 transcriptional signatures and DG histopathology in hippocampal explants surgically obtained from RMTLE patients allowed our group, and others, to portrait the disease as a disturbed network of genegene interactions [15][16][17][18][19] .…”