Proteomic differences in the hippocampus and cortex of epilepsy brain tissue

Abstract

Epilepsy is a common neurological disorder affecting over 70 million people worldwide, with a high rate of pharmaco-resistance, diverse comorbidities including progressive cognitive and behavioral disorders, and increased mortality from direct (e.g., sudden unexpected death in epilepsy, accidents, drowning) or indirect effects of seizures and therapies. Extensive research with animal models and human studies provides limited insights into the mechanisms underlying seizures and epileptogenesis, and these have not translated into significant reductions in pharmaco-resistance, morbidities or mortality. To help define changes in molecular signaling networks associated with seizures in epilepsy with a broad range of etiologies, we examined the proteome of brain samples from epilepsy and control cases. Label-free quantitative mass spectrometry was performed on the hippocampal cornu ammonis 1-3 region (CA1-3), frontal cortex, and dentate gyrus microdissected from epilepsy and control cases (n = 14/group). Epilepsy cases had significant differences in the expression of 777 proteins in the hippocampal CA1-3 region, 296 proteins in the frontal cortex, and 49 proteins in the dentate gyrus in comparison to control cases. Network analysis showed that proteins involved in protein synthesis, mitochondrial function, G-protein signaling, and synaptic plasticity were particularly altered in epilepsy. While protein differences were most pronounced in the hippocampus, similar changes were observed in other brain regions indicating broad proteomic abnormalities in epilepsy. Among the most significantly altered proteins, G-protein subunit beta 1 (GNB1) was one of the most significantly decreased proteins in epilepsy in all regions studied, highlighting the importance of G-protein subunit signaling and G-protein–coupled receptors in epilepsy. Our results provide insights into common molecular mechanisms underlying epilepsy across various etiologies, which may allow for novel targeted therapeutic strategies.

Neuropathology in the North American sudden unexpected death in epilepsy registry

“… 35 , 36 Whole exome sequencing in surgical brain tissue from epilepsy patients that died from SUDEP implicate several gene variants that may increase risk of SUDEP. 58 , 59 We recently identified a number of protein differences between epilepsy and non-epilepsy control cases by localized proteomics in cortex and hippocampal CA1-3 and DG, 60 however found no significant protein differences when comparing SUDEP to epilepsy and few differences in the hippocampus of high-risk SUDEP MTLE cases with a prolonged PGES by RNAseq. 39 Future studies should validate molecular markers to better understand SUDEP risk and to potentially identify novel markers in brain tissue.…”

Proteomic differences in hippocampus and cortex of sudden unexplained death in childhood

“…Case history for the 19 control and 19 SUDC cases is summarized in Table 1 , detailed further in Tables 2 , 3 and Supplementary Table 1, online resource. Group sizes were determined based on the number of cases with significant findings as previously reported [ 33 , 50 , 65 ], including our previous study in epilepsy cases with similar methods [ 60 ].…”

“…Label-free quantitative MS was performed to identify differential protein expression, as described previously [ 43 , 60 ]. Proteins were extracted and digested in each brain region separately in random batches of 16 samples according to S-Trap protocol.…”

“…Our study identified differential expression of proteins in microdissected frontal cortex, hippocampal dentate gyrus (DG), and cornu ammonis (CA1-3) of SUDC cases and control cases with explained causes of death (COD). We evaluated autopsy formalin fixed paraffin embedded (FFPE) tissue to precisely microdissect brain regions from a section, the most readily available from archival autopsy material, and a robust source for proteomics analyses [ 12 – 15 , 20 , 30 , 43 , 60 ]. We identified the molecular signaling pathways associated with protein differences and how these protein changes correlated to SUDC clinical history and neuropathology.…”

Emerging Roles of Non-Coding RNA in Neuronal Function and Dysfunction

“…In Recent Advances in Neurochemistry the majority of instances, seizures can be controlled, however approximately 30% of cases are treatment resistant. Seizures arise from abnormal synchronous activity in hyperexcitable neuronal networks and while this can be attributed to altered electrophysiological properties of ion channels and neurotransmitter systems, converging lines of research have also indicated a central role for the regulation of protein translation [122,123].…”