Epigenetic Landscape of H3K27ac, H3K27me3, H3K4me1, and H3K4me3 Marks in Channel Catfish Following Βeta Glucan Exposure.

Epigenetic regulation plays a central role in shaping innate immune responses following immunostimulant exposure. In this study, we characterized the epigenetic landscape of four histone modifications, H3K27ac, H3K27me3, H3K4me1, and H3K4me3, in the anterior kidney of Ictalurus punctatus (channel catfish) following β-glucan exposure. Using chromatin immunoprecipitation sequencing (ChIP-seq), we generated chromatin state maps and examined the regulatory potential of these histone marks in relation to transcriptional responses. Genes showing increased expression associated with H3K4me3 up-peaks included regulators of metabolism, signaling, pathogen recognition, and immune regulation, while H3K27ac and H3K4me1 marks were linked to genes involved in apoptosis, cytoskeletal dynamics, autophagy, cell adhesion, and stress responses. In contrast, H3K27me3-associated gene repression appeared to fine-tune immune activation by selectively maintaining transcriptional restraint at specific loci. Further transcriptional regulatory-related genes were significantly enriched, suggesting metabolic adaptation following β-glucan exposure. Collectively, these findings define the epigenetic landscape of key histone marks in channel catfish following β-glucan exposure and reveal coordinated chromatin and transcriptional remodeling, consistent with mechanisms of trained immunity. This work provides novel insight into conserved epigenetic features of innate immune memory in teleost fish and supports the use of β-glucan as a functional immunomodulator in aquaculture.