Transcriptome profiling of hippocampal CA1 after early-life seizure-induced preconditioning may elucidate new genetic therapies for epilepsy

Abstract

Injury of the CA1 subregion induced by a single injection of kainic acid (1 × KA) in juvenile animals (P20) is attenuated in animals with two prior sustained neonatal seizures on P6 and P9. To identify gene candidates involved in the spatially protective effects produced by early-life conditioning seizures we profiled and compared the transcriptomes of CA1 subregions from control, 1 × KA- and 3 × KA-treated animals. More genes were regulated following 3 × KA (9.6%) than after 1 × KA (7.1%). Following 1 × KA, genes supporting oxidative stress, growth, development, inflammation and neurotransmission were upregulated (e.g. Cacng1, Nadsyn1, Kcng1, Aven, S100a4, GFAP, Vim, Hrsp12 and Grik1). After 3 × KA, protective genes were differentially over-expressed [e.g. Cat, Gpx7, Gad1, Hspa12A, Foxn1, adenosine A1 receptor, Ca2+ adaptor and homeostasis proteins, Cacnb4, Atp2b2, anti-apoptotic Bcl-2 gene members, intracellular trafficking protein, Grasp and suppressor of cytokine signaling (Socs3)]. Distinct anti-inflammatory interleukins (ILs) not observed in adult tissues [e.g. IL-6 transducer, IL-23 and IL-33 or their receptors (IL-F2)] were also over-expressed. Several transcripts were validated by real-time polymerase chain reaction (QPCR) and immunohistochemistry. QPCR showed that casp 6 was increased after 1 × KA but reduced after 3 × KA; the pro-inflammatory gene Cox1 was either upregulated or unchanged after 1 × KA but reduced by ~70% after 3 × KA. Enhanced GFAP immunostaining following 1 × KA was selectively attenuated in the CA1 subregion after 3 × KA. The observed differential transcriptional responses may contribute to early-life seizure-induced pre-conditioning and neuroprotection by reducing glutamate receptor-mediated Ca2+ permeability of the hippocampus and redirecting inflammatory and apoptotic pathways. These changes could lead to new genetic therapies for epilepsy.

Analysis of gene variants in the GASH/Sal model of epilepsy

“…Discrepancies also occur in drug-induced animal models. No changes in Grik1 expression are observed in animal models induced by pilocarpine administration, whereas Grik1 is upregulated when inducing an injury in the CA1 subregion by a single injection of kainic acid in juvenile rats with previously sustained neonatal seizures [54,55]. Moreover, Cacna1a and Grick 1, together with Grin2c, participate in the glutamatergic synapse pathway, which is significantly enriched in the GASH/Sal model.…”

Neonicotinoid Insecticides Alter the Gene Expression Profile of Neuron-Enriched Cultures from Neonatal Rat Cerebellum

“…The Cacng1 gene expressed in human fetal and adult brain [43] and developing mouse cerebellum [44]. A mutation of this gene was also proposed as a candidate for epilepsy [45] and its expression in hippocampal CA1 is altered in drug-induced epilepsy [46]. Another common DE gene, F2rl2 (Par3) belongs to an important subfamily of GPCRs, that are correlated with various phases of neurodevelopment [47,48,49,50], including axon-dendrite differentiation [51].…”

Early life seizures: Evidence for chronic deficits linked to autism and intellectual disability across species and models

“…Altered HCN channel expression and function after HT ELS correlates with later SRS in this model (Dube et al, 2009a; Noam et al, 2011) but also could contribute to ASD/ID. Transcriptome profiling following ELS has also been pursued (Friedman et al, 2013; Theilhaber et al, 2013). It is likely that several of these alterations in cellular mechanisms contribute to the ASD/ID phenotype, while others are reactionary changes in response to ELS, SRS, ID and/or ASD and do not contribute to the phenotype.…”