Ovary removal modifies liver message RNA profiles in single Comb White Leghorn chickens

Abstract

Ovaries produce sex hormones, and ovariectomized animals are often used as models for ovarian dysfunction. The liver is a vital organ involved in metabolism and immunity. In the present study, we conducted experiments to investigate the effects of ovariectomy on transcription and metabolic processes in the liver in chicken. Eight Single Comb White Leghorn (SCWL) female chickens were ovariectomized at 17 wk of age, and 8 intact SCWL females served as controls. At 100 wk of age, all chickens were euthanized. High-throughput transcriptome sequencing was performed on liver RNA obtained from ovariectomized and intact females. A total of 267 differentially expressed genes (DEG) were identified in our study. After analysis using DAVID functional annotation tool, one significant Kyoto Encyclopedia of Genes and Genomes pathway, the phosphatidylinositol signaling pathway, was clustered. Gene Ontology enrichment analysis yielded 46 significant Gene Ontology terms. Among terms describing biological processes, the glycerolipid metabolic and lipid localization processes were dominant. The anabolic genes, PEPCK and GK5, and the catabolic genes, VTG1; VTG2; PLD5; DGKQ; DGKE; and FABP3, were detected in ovariectomized chickens. Differentially expressed genes such as ENSGALG00000000162, IL-1Β, SVOPL, and CA12 implied that livers in ovariectomized chickens were subjected to strong inflammatory reactions, whereas defenses against endogenous materials were compromised. A comprehensive view of gene expression in the liver of ovariectomized chickens would advance our understanding of lipid metabolism, glycometabolism, and their relationships to pathologies induced by absence of the ovary. The identified DEG indicated that ovariectomy disturbed lipid metabolism in the liver and was accompanied by an increase in hepatic gluconeogenesis and reductions in phosphatidic acid synthesis and lipid carrier capacity.

Keywords: RNA-seq; liver mRNA profile; ovariectomy; single Comb White Leghorn chicken.

Figure 1

Differentially expressed genes in ovariectomized (Tr_O) vs. intact (Co_I) hens. (A) Volcano plot showing differentially expressed genes. The x-axis shows log₂ of the expression ratio, and the y-axis shows adjusted P-value. Red dots represent genes that are expressed at significantly higher levels in ovariectomized animals, and green dots represent genes with significantly lower relative expression. Genes classified as having no significant differences in gene regulation are represented using blue dots. (B) Venn diagram representing 267 DEG, identified in: ovariectomized and intact animals (250), ovariectomized animals only (1), and intact animals only (16). Abbreviation: DEG, differentially expressed gene.

Figure 2

Most significantly enriched GO terms associated with differentially expressed genes between ovariectomized and intact females. P-value of 0.05 and Fold Enrichment above 2 were used as threshold for significant enrichment. The x-axis shows the number of genes in each category. Red, biological processes; blue, cellular components; green, molecular functions.

Figure 3

Quantitative validation of differentially expressed genes between ovariectomized and intact females. (A) Relative expression for 8 selected genes. Black blocks mean gene relative expressions in ovariectomized group, grey blocks mean gene relative expressions in intact group. * means significant difference (P < 0.05). (B) Comparison of RT-qPCR and RNA-Seq results. Expression change folds of the 8 selected genes were calculated according to RNA-Seq and RT-qPCR results separately. Y-axis shows gene expression change folds of ovariectomized relative to intact group. Positive means gene expressions were increased in ovariectomized group. Negative means gene expressions were reduced in ovariectomized group. Red line shows gene expression change folds from RNA-Seq, blue line shows gene expression change folds from RT-qPCR.

Supplementary Figure S1

Pearson correlation between samples.