Molecular characteristics of FABP3 and FABP4 genes and tissue expression analysis of Guanling cattle

【Objective】To investigate molecular characteristics of heart-type fatty acid binding protein（FABP3）and fatty acid binding protein（FABP4）genes and their expression in different age groups and different tissues in Guanling cattle，so as to provide a theoretical basis for revealing mechanism of fatty acid regulation by FABP3 and FABP4 genes in cattle.【Method】 The protein coding region（CDS）sequences of FABP3 and FABP4 genes in Guanling cattle were amplified by RT-PCR，and bioinformatics analysis was performed using online software such as ProtScale，ProtParam，SOPMA，SWISS-MODEL，TMHMM-2.0，SignalP-5.0 and NetPhos-3.1.The expression of FABP3 and FABP4 genes in various tissues of 3-day-old Guanyin calves，24-month-old Guanyin cattle（adults）and 24-month-old crossbred cattle（Guanyin cattle×Limousin cattle）was examined by quantitative real-time PCR（qRT-PCR）.【Result】 The CDS sequences of Guanling cattle FABP3 and FABP4 genes were 402 and 399 bp long，encoding 133 and 132 amino acid residues respectively.Their protein secondary and tertiary structures were mainly irregularly coiled and extended chains without transmembrane structural domains or signal peptide shear sites，and they were stable hydrophilic proteins.FABP3 and FABP4 amino acid sequences had 26 and 21 phosphorylation sites，respectively，among which threonine was more widely distributed； the proteins of FABP3 and FABP4 had interactions with FABP1，FABP6，peroxisome proliferator-activated receptor γ（PPARγ），lipoprotein lipase（LPL）and hormone-sensitive lipase（LIPE）.Phylogenetic trees based on amino acid sequence similarity between FABP3 and FABP4 showed that Guanling cattle were most closely related to yaks，followed by sheep，and more distantly related to chickens and zebrafish.FABP3 and FABP4 genes were differentially expressed in all tissues of Guanling and crossbred cattle.The relative expression of FABP3 gene was the highest in the heart and was significantly higher in adult Guanling cattle than in calves and crossbred cattle（P<0.01，the same below）； the relative expression of FABP4 gene was the highest in fat and was significantly higher in calves than in adult Guanling cattle.The relative expression of FABP4 gene was the highest in fat，and the relative expression in calves was significantly higher than that in adult Guanling cattle.【Conclusion】 FABP3 and FABP4 genes in Guanling cattle，genetically conserved，are expressed at higher levels in heart and fat，and they are closely related to fatty acid metabolism.