Abstract
Few studies have been conducted regarding the biological function and regulation role of gga-miR-221-5p in the liver. We compared the conservation of miR-221-5p among species and investigated the expression pattern of gga-miR-221-5p, validating the direct target genes of gga-miR-221-5p by dual luciferase reporter assay, the biological function of gga-miR-221-5p in the liver was studied by gga-miR-221-5p overexpression and inhibition. Furthermore, we explored the regulation of gga-miR-221-5p and its target genes by treatment with estrogen and estrogen antagonists in vivo and in vitro. The results showed that miR-221-5p was highly conserved among species, expressed in all tested tissues and significantly downregulated in peak-laying hen liver compared to pre-laying hen liver. Gga-miR-221-5p could directly target the expression of elongase of very long chain fatty acids 6 (ELOVL6) and squalene epoxidase (SQLE) genes to affect triglyceride and total cholesterol content in the liver. 17β-estradiol could significantly inhibit the expression of gga-miR-221-5p but promote the expression of ELOVL6 and SQLE genes. In conclusion, the highly conservative gga-miR-221-5p could directly target ELOVL6 and SQLE mRNAs to affect the level of intracellular triglyceride and total cholesterol. Meanwhile, 17β-estradiol could repress the expression of gga-miR-221-5p but increase the expression of ELOVL6 and SQLE, therefore promoting the synthesis of intracellular triglyceride and cholesterol levels in the liver of egg-laying chicken.
Highlights
IntroductionMicroRNAs (miRNAs) are small, endogenous, non-coding single-strand RNAs that post-transcriptionally regulate gene expression by binding to the 3 untranslated regions (3 UTR) of potentially hundreds of mRNAs. miRNAs are about 22 nucleotides (nt) in length [1,2], and the 2nd–8th nt of the 5 end of miRNA, named the seed region, are crucial for recognizing and binding to target genes [3,4]. miRNAs regulate their target mRNAs by mRNA molecule degradation or translation inhibition [5,6].Increasingly many investigations suggest that miRNAs are involved in various biological processes
MicroRNAs are small, endogenous, non-coding single-strand RNAs that post-transcriptionally regulate gene expression by binding to the 3 untranslated regions (3 UTR) of potentially hundreds of mRNAs. miRNAs are about 22 nucleotides in length [1,2], and the 2nd–8th nt of the 5 end of miRNA, named the seed region, are crucial for recognizing and binding to target genes [3,4]. miRNAs regulate their target mRNAs by mRNA molecule degradation or translation inhibition [5,6].Increasingly many investigations suggest that miRNAs are involved in various biological processes
The analysis of miRNA transcriptomes in Marek’s disease (MD) lymphoma showed that gga-miR-221-5p was significantly downregulated in MD lymphoma, and gga-miR-221-5p inhibited the proliferation of MDV-transformed lymphoid cell line (MSB1), suggesting that gga-miR-221-5p had an anti-cancer effect [27]
Summary
MicroRNAs (miRNAs) are small, endogenous, non-coding single-strand RNAs that post-transcriptionally regulate gene expression by binding to the 3 untranslated regions (3 UTR) of potentially hundreds of mRNAs. miRNAs are about 22 nucleotides (nt) in length [1,2], and the 2nd–8th nt of the 5 end of miRNA, named the seed region, are crucial for recognizing and binding to target genes [3,4]. miRNAs regulate their target mRNAs by mRNA molecule degradation or translation inhibition [5,6].Increasingly many investigations suggest that miRNAs are involved in various biological processes. Recent studies report that miRNAs exert a biological function in metabolic and endocrine pathways [7] and adipogenesis [8,9]. Emerging evidence shows that miRNAs act as key regulators for hepatic lipid metabolism. The liver-specific miR-122 in mammals is abundantly expressed in liver [10] and can control the hepatic fatty acids and cholesterol synthesis by repressing the expression of mRNAs involved in the cholesterol biosynthesis pathway [11]. MiR-33 can regulate the biological metabolism process of the liver by affecting cholesterol efflux and high-density lipoprotein metabolism [12]. Gga-miR-22-3p and gga-miR-101-2-5p are involved in the hepatic lipid metabolism by targeting the key factors Elovl and Apolipoprotein B (ApoB) of the lipid metabolism pathway [13,14]. Most of the studies about miRNA functions are mainly focused on mammals, the action mechanisms of most miRNAs in chicken are unclear
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