Genome-Wide Analysis of the FABP Gene Family in Liver of Chicken (Gallus gallus): Identification,Dynamic Expression Profile, and RegulatoryMechanism.

Wang Wang,Yang Yang,Kang Kang,Liu Liu,Tian Tian,Li Li,Yue Yue

doi:10.3390/ijms20235948

Wang Wang, Yang Yang + Show 5 more

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https://doi.org/10.3390/ijms20235948

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Abstract

The fatty acid-binding protein (FABP) gene family, which encodes a group of fatty acid-trafficking molecules that affect cellular functions, has been studied extensively in mammals. However, little is known about the gene structure, expression profile, and regulatory mechanism of the gene family in chickens. In the present study, bioinformatics-based methods were used to identify the family members and investigate their evolutionary history and features of gene structure. Real-time PCR combined with in vivo and in vitro experiments were used to examine the spatiotemporal expression pattern, and explore the regulatory mechanism of FABP genes. The results show that nine members of the FABP gene family, which branched into two clusters and shared a conserved FATTYACIDBP domain, exist in the genome of chickens. Of these, seven FABP genes, including FABP1, FABP3-7, and FABP10 were abundantly expressed in the liver of hens. The expression levels of FABP1, FABP3, and FABP10 were significantly increased, FABP5 and FABP7 were significantly decreased, and FABP4 and FABP6 remained unchanged in hens at the peak laying stage in comparison to those at the pre-laying stage. Transcription of FABP1 and FABP3 were activated by estrogen via estrogen receptor (ER) α, whilst FABP10 was activated by estrogen via ERβ. Meanwhile, the expression of FABP1 was regulated by peroxisome proliferator activated receptor (PPAR) isoforms, of which tested PPARα and PPARβ agonists significantly inhibited the expression of FABP1, while tested PPARγ agonists significantly increased the expression of FABP1, but downregulated it when the concentration of the PPARγ agonist reached 100 nM. The expression of FABP3 was upregulated via tested PPARβ and PPARγ agonists, and the expression of FABP7 was selectively promoted via PPARγ. The expression of FABP10 was activated by all of the three tested PPAR agonists, but the expression of FABP4-6 was not affected by any of the PPAR agonists. In conclusion, members of the FABP gene family in chickens shared similar functional domains, gene structures, and evolutionary histories with mammalian species, but exhibited varying expression profiles and regulatory mechanisms. The results provide a valuable resource for better understanding the biological functions of individual FABP genes in chickens.

Highlights

Fatty acids (FAs) serve in fat synthesis, assembly, and storage in different cellular substructures including the mitochondria, peroxisome, endoplasmic reticulum, lipid droplet, and nucleus [1]
The results suggest that two proteins, namely, CRABP1 (NP_001025710.1) and CRABP2 (XP_015153912.1), belong to the cellular retinoic acid-binding proteins (CRABPs) family, and three proteins; namely, RBP1 (NP_001264345.1), RBP2 (NP_001264346.1), and RBP7 (XP_417606.4), belong to the RBP family, with the five proteins clustered in a distinct group (Figure 1)
We found that FABP3 mRNA levels were positively affected byPPARβ and PPARγ agonists, the transcripts of FABP7 were only activated by tested PPARγagonists, and FABP10 responded positively to all tested peroxisome proliferator activated receptor (PPAR) agonists, but the expression levels of FABP1 declined continuously as the concentrations of WY14,643 and GW0,742, agonists of PPARα and PPARβ, respectively, increased, agreeing with the previous study which concluded that tested PPAR-isoform agonists can perform the actions mediated by PPARs and upregulate the expression of target genes at the transcriptional level [33].Previous studies demonstrated that PPARγ mRNA level is reduced upon exposure to high concentrations of PPARγ agonists (>10 μM), including rosiglitazone and pioglitazonein HepG2 cells [70]

Summary

Introduction

Fatty acids (FAs) serve in fat synthesis, assembly, and storage in different cellular substructures including the mitochondria, peroxisome, endoplasmic reticulum, lipid droplet, and nucleus [1] Their hydrophobic nature requires carrier protein assistance for FA transport.The FABP gene family can bind long-chain fatty acids (LCFAs) (C12-20), suppress the stain remover-like properties of FA, and traffic these ligands to various cellular compartments [2]. All vertebrate FABP genes possess four exons separated by three introns [7], and contain a classical three-element finger print domain shared by three motifs termed FATTYACIDBP 1-3 (Kyoto Encyclopedia of Genes and Genomes; PRINTS: PR00178) [8] These motifs have a low homology, they still share a similar β-barrel tertiary structure, which is designed to provide an internal cavity that serves as a binding site for hydrophobic ligands [9]. Under high-fat diet conditions, male FABP2-null mice exhibited increased hepatic triacylglycerol (TG) deposition, as compared to corresponding wild-type mice, which may be associated with the specific role of FABP2 in intestinal TG synthesis and/or transport [19]

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