Alterations in DNA 5-hydroxymethylation patterns in the hippocampus of an experimental model of chronic epilepsy

• Published in: Neurobiology of disease 2024-10, Vol.200, p.106638, Article 106638
• Main Authors: Bahabry, Rudhab, Hauser, Rebecca M., Sánchez, Richard G., Jago, Silvienne Sint, Ianov, Lara, Stuckey, Remy J., Parrish, R. Ryley, Ver Hoef, Lawrence, Lubin, Farah D.
• Format: Article
• Language: English
• Subjects: 5-Methylcytosine - analogs & derivatives; 5-Methylcytosine - metabolism; Adult; Animals; Bdnf; Disease Models, Animal; DNA Methylation; Epigenesis, Genetic; Epigenetics; Epilepsy; Epilepsy, Temporal Lobe - genetics; Epilepsy, Temporal Lobe - metabolism; Female; Hippocampus - metabolism; hMeDIP; Humans; Hydroxymethylation; Kainic Acid; Male; Rats; Rats, Sprague-Dawley; Sequencing; TET
• ISSN: 0969-9961; 1095-953X; 1095-953X
• DOI: 10.1016/j.nbd.2024.106638

Temporal lobe epilepsy (TLE) is a type of focal epilepsy characterized by spontaneous recurrent seizures originating from the hippocampus. The epigenetic reprogramming hypothesis of epileptogenesis suggests that the development of TLE is associated with alterations in gene transcription changes resulting in a hyperexcitable network in TLE. DNA 5-methylcytosine (5-mC) is an epigenetic mechanism that has been associated with chronic epilepsy. However, the contribution of 5-hydroxymethylcytosine (5-hmC), a product of 5-mC demethylation by the Ten-Eleven Translocation (TET) family proteins in chronic TLE is poorly understood. 5-hmC is abundant in the brain and acts as a stable epigenetic mark altering gene expression through several mechanisms. Here, we found that the levels of bulk DNA 5-hmC but not 5-mC were significantly reduced in the hippocampus of human TLE patients and in the kainic acid (KA) TLE rat model. Using 5-hmC hMeDIP-sequencing, we characterized 5-hmC distribution across the genome and found bidirectional regulation of 5-hmC at intergenic regions within gene bodies. We found that hypohydroxymethylated 5-hmC intergenic regions were associated with several epilepsy-related genes, including Gal, SV2, and Kcnj11 and hyperdroxymethylation 5-hmC intergenic regions were associated with Gad65, TLR4, and Bdnf gene expression. Mechanistically, Tet1 knockdown in the hippocampus was sufficient to decrease 5-hmC levels and increase seizure susceptibility following KA administration. In contrast, Tet1 overexpression in the hippocampus resulted in increased 5-hmC levels associated with improved seizure resiliency in response to KA. These findings suggest an important role for 5-hmC as an epigenetic regulator of epilepsy that can be manipulated to influence seizure outcomes. [Display omitted] •Reduced hippocampal DNA 5-hydroxymethylation levels were found in the hippocampus of people with temporal lobe epilepsy.•In the rodent experimental model of temporal lobe epilepsy, we recapitulated DNA 5-hydroxymethylation findings in human temporal lobe epilepsy.•Post-status epilepticus, the majority of genomic DNA 5-hydroxymethylation loss in the hippocampus occurs within intergenic regions.•Differential DNA 5-hydroxymethylation was found at gene regions involved in neuronal and synaptic regulation.•Manipulating TET1 expression in the rat hippocampus promotes seizure susceptibility and resiliency.