| Transcription factors FoxO subfamily belong to the forkhead family. FoxO subfamily contains four members(FoxO1,FoxO3,FoxO4 and FoxO6).Transcriptional activity of FoxO proteins is regulated through insulin-phosphatidylinositol 3-kinase AKT/PKB signaling pathway.FoxO regulated proliferation and differentiation of myoblast and adipocytes.FoxO proteins were involved in muscular atrophy and skeletal muscle metabolism.The bovine FoxOs cDNA sequences were obtained by RT-PCR and sequencing. Nucleotide sequences of FoxO1 (2424bp),FoxO3 (1876bp) and FoxO4 gene(2211bp) encoded different amino acids,respectively. The bovine FoxO1, FoxO3, FoxO4 amino acid sequence of identities were higher with pig (93%,98%,93%), followed by the human (93%,96%,87%), mice (90%,94%,84%). Bioinformatics analysis showed that the physical and chemical properties of protein molecule of FoxO1, FoxO3, and FoxO4 wre similar,they were unstable acid protein. FoxO1, FoxO3 and FoxO4 had phosphorlation sites, N-glycosylation sites, O-glycosylation sites, but no transmembrane domain. The secondary structure mainly consisted of Alpha heli, extended strand and random coil. Conserved structure domain prediction found that all the three proteins had the Forkhead domain of 95 amino acid residues, a nuclear localization signal and nuclear export signal, and the possibility that the FoxO1, FoxO3, FoxO4 protein located in the nucleus was 94.1%.We adopted the real-time PCR technology to test the expression quantity of FoxO1, FoxO3 and FoxO4 gene of Simmental crossbred cattle in different tiusses.We also tested the expression quantity of FoxO1, FoxO3 and FoxO4 gene of Simmental crossbred cattle in different growth point. Relative expression quantity of FoxO1 gene was the highest in muscle tissues, followed in the subcutaneous fat, abdominal fat, heart, kidney, while the expression quantity was comparatively lower in spleen and liver. Expression of FoxO3 gene was high in muscle tissue as compared to other tissues, followed by heart and kidney, and low in liver, spleen, subcutaneous fat, and abdominal fat. Expression of FoxO4 gene was most abundant in muscle tissues. Expression pattern of FoxO1, FoxO3 and Fox04 gene varied in different tissues of in the growth of Simmental crossbred cattle. There was advantageous growth point for gene expression in acertain tissue. We analysed correlation of gene expression quantity and meat quality traits. The results indicated that FoxO1 gene was significantly negatively related with muscle fiber area.FoxO3 Expression was significantly related to muscle fiber density, fiber area and fiber diameter. FoxO4 expression was significantly positively correlated with muscle fiber diameter and muscle fiber area.The SNPs was detected in FoxOs gene with three bovine poplutions by direct sequencing.We found eight polymorphisms that were located in exon3 of FoxO1 (nt250370C>T,nt250433T>C,nt250463A>G,nt250499G>A,nt250544OA,nt250661T>C,nt 250920C＞T,nt251031G>A).The 8 SNP sites constituted 9 haplotypes,and H1 (CCAACTCG) and H3 (CCAACTCA) were the dominant haplotypes. The 9 haplotypes formed 15 diplotypes.The genetic effect analysis of FoxO1 gene diplotype and meat quality traits indicated that the diplotype had significant gentic effects on shear force,fibers diameter and fibers density. Diplotype H3H4 had the lowest shear force and muscle fiber diameter and the highest density of muscle fibers, thus it had a positive effect on the meat quality.Eight polymorphisms were identified in FoxO3 (nt 190010C＜T,nt189659C＞T, nt189656C＞T, nt189584G>A, nt189476C＞A, nt189302A>G, nt189233C＞T,nt188968G>C). Their locations were in exon2 of FoxO3.The 8 SNPs formed 12 haplotypes, and H1 (CCCGCACG) haplotype frequency was the highest, accounting for 71.25%. Thirteen diplotypes were obtained based on these 12 haplotypes. The genetic effect analysis of diplotype and meat quality traits indicated that the diplotype had significant gentic effects on intramuscular fat content,fibers diameter and fibers density. Diplotype H1H6 had the lowest shear force, the highest density of muscle fiber and the smallest muscle fiber diameter, and such diplotype had a positive effect on beef tenderness.Only one polymorphic site was detected in FoxO4 gene(nt454949 G> A), located in the exon2 region. There was two kinds of haplotypes that H1(G) haplotype frequency was much higher than the H2 (A). The genetic effect analysis of FoxO4 gene diplotype and meat quality traits indicated that the diplotype had significant gentic effects on fibers diameter and fibers density.Diplotype H2H2 had lower muscle fiber diameter and higher fiber density, and it had a positive effect on the meat quality. |
