Epigenetic Regulation of Adaptive Thermotolerance in Nigerian Indigenous Chicken Ecotypes: Mechanisms and Implications

This study investigates epigenetic mechanisms underlying adaptive thermotolerance in Nigerian indigenous chicken ecotypes compared with commercial broiler lines, developing an original understanding of epigenetically encoded heat adaptation that is relevant to climate-resilient poultry breeding. Nigerian indigenous chickens survive and reproduce under tropical heat conditions that severely compromise commercial broiler performance, but the molecular mechanisms of their thermal adaptation beyond simple genetic differences are unexplored. This study uses a comparative epigenomics approach, conducting whole genome bisulfite sequencing for DNA methylation profiling, ChIP-seq for active and repressive histone modifications, and ATAC-seq for chromatin accessibility analysis in hypothalamic, hepatic, and skeletal muscle tissues of indigenous ecotype chickens, commercial Ross 308 broilers, and their F1 crosses, before and during experimental heat stress (38 degrees Celsius for 6 hours daily for 14 days). Differential methylation analysis, chromatin state mapping, and transcription factor binding site enrichment are performed. Findings reveal significantly higher baseline methylation of heat stress-responsive gene promoters in commercial broilers compared to indigenous ecotypes, associated with greater transcriptional flexibility in indigenous birds during heat challenge. Heat shock protein 70, aquaporin, and uncoupling protein genes show epigenetically regulated expression differences that explain divergent thermal physiological responses. Stably heritable epigenetic marks are detected in F1 crosses following parental heat stress experience. The study contributes an original epigenomic thermotolerance model for Nigerian poultry and recommends epigenetic biomarker development for heat-resilient breeding.

Keywords: epigenetics, thermotolerance, Nigerian indigenous chickens, DNA methylation, heat stress.