Cloning and tissue expression analysis of Guanling cattle FABP1 and FABP2 genes

【Objective】 The molecular characteristics of liver-type fatty acid binding protein（FABP1）and intestinaltype fatty acid binding protein（FABP2）genes and their expression in various tissues of cattle of different ages and breeds were clarified to provide a theoretical basis for subsequent studies on the mechanisms of the regulatory effects of FABP1 and FABP2 on bovine fatty acids.【Method】 The sequences of the coding regions（CDS）of FABP1 and FABP2 genes in Guanling cattle were amplified by RT-PCR，and bioinformatics analysis was performed by online softwares such as ProtParam， ProtScale， SOPMA， SWISS-MODEL， TMHMM-2.0， SignalP-5.0 and NetPhos-3.1， and the expression of FABP1 and FABP2 genes in various tissues of 3-day-old Guanling cattle（calves），24-month-old Guanling cattle（adults）and 24-month-old crossbred cattle（Guanling cattle×Limousin cattle）was examined by real-time fluorescence quantitative PCR.【Result】 The full-length CDS sequences of FABP1 and FABP2 genes were 384 and 399 bp，respectively，encoding 127 and 132 amino acid residues. The secondary and tertiary structures of their encoded proteins were dominated by random coil and extended chain without transmembrane structural domains and signal peptide shear sites，and they were hydrophilic stable proteins. The amino acid sequences of FABP1 and FABP2 contained 19 and 18 phosphorylation sites respectively，of which threonine was widely distributed in both amino acid sequences. Homology comparison and phylogenetic evolutionary analysis of the amino acid sequences of FABP1 and FABP2 showed that Guanling cattle were closely related to horses，sheep and goats，while they were more distantly related to chickens and ducks，and the similarities with other species were also above 75.0%. FABP1 and FABP2 genes were expressed in all tissues of cattle of different ages and breeds，among which，the relative expression of FABP1 gene was higher in liver and small intestine，and the relative expression of FABP1 gene in several tissues of calves and crossbred cattle was extremely significantly higher than that of adult Guanling cattle（P<0.01，the same below）. The FABP2 gene was highly expressed mainly in the small intestine，and the relative expression of FABP2 gene in the small intestine of adult Guanling cattle was extremely significantly higher than that of calves and significantly higher than that of crossbred cattle（P<0.05）.【Conclusion】FABP1 and FABP2 genes are highly conserved in Guanling cattle and are expressed in different age stages and tissues，especially in the liver and small intestine，so it is hypothesized that FABP1 and FABP2 genes synergistically regulate fatty acid anabolism in Guanling cattle.