Top Common Differentially Expressed Genes in the Epileptogenic Nucleus of Two Strains of Rodents Susceptible to Audiogenic Seizures: WAR and GASH/Sal.

Samara Damasceno,Faustino Marín,Manuel Javier Herrero-Turrión,Ricardo Gómez-Nieto,Norberto Garcia-Cairasco,Dolores E. Lopéz

doi:10.3389/fneur.2020.00033

Abstract

The Wistar Audiogenic Rat (WAR) and the Genetic Audiogenic Seizure Hamster from Salamanca (GASH/Sal) strains are audiogenic epilepsy models, in which seizures are triggered by acoustic stimulation. These strains were developed by selective reproduction and have a genetic background with minimal or no variation. In the current study, we evaluated the transcriptome of the inferior colliculus, the epileptogenic nucleus, of both audiogenic models, in order to get insights into common molecular aspects associated to their epileptic phenotype. Based on GASH/Sal RNA-Seq and WAR microarray data, we performed a comparative analysis that includes selection and functional annotation of differentially regulated genes in each model, transcriptional evaluation by quantitative reverse transcription PCR of common genes identified in both transcriptomes and immunohistochemistry. The microarray data revealed 71 genes with differential expression in WAR, and the RNA-Seq data revealed 64 genes in GASH/Sal, showing common genes in both models. Analysis of transcripts showed that Egr3 was overexpressed in WAR and GASH/Sal after audiogenic seizures. The Npy, Rgs2, Ttr, and Abcb1a genes presented the same transcriptional profile in the WAR, being overexpressed in the naïve and stimulated WAR in relation to their controls. Npy appeared overexpressed only in the naïve GASH/Sal compared to its control, while Rgs2 and Ttr genes appeared overexpressed in naïve GASH/Sal and overexpressed after audiogenic seizure. No statistical difference was observed in the expression of Abcb1a in the GASH/Sal model. Compared to control animals, the immunohistochemical analysis of the inferior colliculus showed an increased immunoreactivity for NPY, RGS2, and TTR in both audiogenic models. Our data suggest that WAR and GASH/Sal strains have a difference in the timing of gene expression after seizure, in which GASH/Sal seems to respond more quickly. The transcriptional profile of the Npy, Rgs2, and Ttr genes under free-seizure conditions in both audiogenic models indicates an intrinsic expression already established in the strains. Our findings suggest that these genes may be causing small changes in different biological processes involved in seizure occurrence and response, and indirectly contributing to the susceptibility of the WAR and GASH/Sal models to audiogenic seizures.

Highlights

Epilepsy is a neurological condition determined by enduring predisposition to generate seizures and by its neurobiological, cognitive, psychological, and social consequences [1, 2]
The animals were subdivided into four groups: [1] the naïve control group (Wistar N and Syrian N; n = 7 per strain); [2] the naïve audiogenic group (WAR N and GASH/Sal N; n = 7 per strain) corresponding to seizure-prone animals that did not receive any acoustic stimulation or developed any seizures; [3] the stimulated control group (Wistar S and Syrian S; n = 6 per strain), composed of Wistar rats and Syrian hamsters subjected to acoustic stimulation; and [4] the stimulated audiogenic group (WAR S and GASH/Sal S; n = 7 per strain) corresponding to seizure-prone animals that were subjected to acoustic stimulation and presented a convulsive episode
It is noteworthy that the category “transcription regulator activity” was found the third most represented in GASH/Sal, showing 11 differentially expressed genes, Early Growth Response 1, 2, 3, and 4 (Egr1; Egr2; Early Growth Response 3 (Egr3); Egr4), SERTA domain containing 1 (Sertad1), Neuronal PAS domain protein 4 (Npas4), TNF receptor associated factor 5 (Traf5), Kruppel-like factor 7 and 10 (Klf7; Klf10), and AP-1 transcription factor subunit (Jun; Junb), whereas in WAR, the same category was represented only by the Egr3 gene

Summary

Introduction

Epilepsy is a neurological condition determined by enduring predisposition to generate seizures and by its neurobiological, cognitive, psychological, and social consequences [1, 2]. Experimental animal models are indispensable for epilepsy research and can be developed through induction of seizures in wild-type animals or inbreeding genetically epilepsyprone animals [6, 7]. The genetically seizure-prone models are maintained using inbreeding protocols and have a genetic background with minimal or no variation. These models may provide important molecular and genetic clues to uncover the development of epilepsy and the occurrence of seizures. Among the genetic models of epilepsy, there are the audiogenic models whose animals are susceptible to seizures triggered by acoustic stimulation, named audiogenic seizures

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Conclusion