Transcriptional Profiling of the Chicken Liver during the Embryo-to-Hatchling Metabolic Transition

In the present study, we examined the hepatic transcriptome of chickens during the peri-hatch periodor the metabolic jump from chorioallantoic (embryo) to pulmonary (hatchling) respiration. Although our major interest was comparison of differentially-expressed genes between embryos and hatchlings, we made pairwise contrasts across six developmental ages. We collected the liver from four embryos at three ages (e16, e18 and e20) and four hatchling chicks at three ages (1, 3 and 9 days) post hatching. Liver samples (N=24) were used for extraction of total RNA which was then used for hybridization to 24 Affymetrix Chicken Genome Arrays. Ingenuity Pathways Analysis was used for functional annotation and mapping of differentially expressed (FDR0.05) genes to canonical pathways and gene interaction networks. We identified 1274 hepatic genes that were differentially expressed between embryos and hatchling chicks and of these, 284 genes are involved in lipid metabolism. The three most abundant found in liver of embryos were (MOGAT1, DIO3 and PDK4), whereas THRSP, FASN and DIO2 were greatly expressed in liver of hatchlings. Two functionally-distinct clusters of hepatic genes have emerged from our time-course transcriptional scans in the peri-hatch chicken. Cluster A genes are largely lipolytic with higher expression in the embryo, while Cluster B genes are mainly lipogenic and thermogenic with greater expression in liver of hatchlings. The present study describes the innate chorography of transcriptional responses of liver to the abrupt metabolic switch from aquatic ectothermy (embryos) to free-living endothermy (hatchling chicks).

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Cogburn LA, Trakooljul N, Chen C, Huang H, Wu CH, Carré W, Wang X, White HB 3rd