Unique Genetic Responses Revealed in RNA-Seq from the Spleen of Chickens Stimulated with Lipopolysaccharide and Heat

Climate change and disease have large negative impacts on poultry production, but little is known about the interactions of these stressors in chickens. Fayoumi (heat and disease resistant) and broiler (heat and disease susceptible) chicken lines were stimulated at 22 days of age, using a 2x2x2 factorial design including: breed (Fayoumi or broiler), inflammatory stimulus [lipopolysaccharide (LPS) or saline], and heat (35°C or 25°C). Spleens were harvested 3.5 hours post stimulus and then analyzed for transcriptional changes using RNA-sequencing on the Illumina HiSeq 2500. Four individual cDNA libraries were sequenced per treatment. An average of 22 million reads were generated per library. We considered differentially expressed genes (DEG) with log₂ fold change ≥ 2 and FDR ≤ 0.05.

Stimulation with LPS induced more DEG in the broiler (N=283) than the Fayoumi (N=85), whereas heat treatment resulted in fewer DEG in broiler (N=22) compared to Fayoumi (N=107). The largest changes in gene expression were identified in the double stimulus (LPS+heat) for which broiler had many DEG (N=567) and the Fayoumi had even more (N=1471). Both breeds shared many DEG in response to LPS+heat (399). Further investigation into the unique Fayoumi response to the double stimulus, resulted in observed enriched pathways including apoptosis, steroid hormone biosynthesis, and cytokine-cytokine receptor interaction, and whereas the unique broiler response resulted in the observed enriched cytokine-cytokine receptor interaction pathway. The genes and pathways identified may serve as biomarkers for genetic selection for heat and disease tolerant chickens. Support: USDA-NIFA-AFRI grant and Hatch project #5358.