Phagocytic Function Analyses of GAB_BR-Related Microglia in Immature Developing Epileptic Brain Based on 10× Single-Nucleus RNA Sequencing Technology

<b>Background</b>: Epilepsy is a neurological disorder defined by the occurrence of epileptic seizures, which can significantly affect children, often leading to learning and cognitive impairments. Microglia, the resident immune cells of the central nervous system, are essential in clearing damaged neurons through phagocytosis. Notably, GAB_BR-associated microglia have been implicated in regulating phagocytic activity. Since the phagocytic function of microglia is critical in the pathogenesis of epilepsy, this study aims to investigate the role of GAB_BR-associated microglia in the development of the immature brain following epileptic seizures. <b>Methods:</b> Epilepsy was induced in a mouse model by the intraperitoneal injection of KA. Changes in the expression of the GAB_BR-related gene, GAB_BR2, in hippocampal microglia were analyzed using single-nucleus RNA sequencing (snRNA-seq). Cognitive and emotional changes in the mice were assessed through behavioral analyses. The expression of GAB_BR2 was semi-quantitatively measured using Western blotting, quantitative reverse transcription PCR, and immunofluorescence. Additionally, the spatial relationship between GAB_BR2 and hippocampal neurons was evaluated using Imaris software. <b>Results:</b> The snRNA-seq analysis revealed that GAB_BR2 expression was elevated in activated microglia in the hippocampus during chronic epilepsy compared to the early phase of seizures. Behavioral assessments demonstrated heightened anxiety levels and learning and memory impairments in the chronic epilepsy group compared to the control group. GAB_BR2 expression was upregulated in chronic epilepsy. Three-dimensional reconstruction analyses revealed a significantly increased contact volume between GAB_BR-associated microglia and neurons in the chronic epilepsy group compared to the control group. <b>Conclusions</b>: GAB_BR-associated microglia significantly contribute to the progression of immature brain diseases by promoting neuronal phagocytic activity.