Tissue Expression Pattern And Genetic Variation Analysis Of FOXA2Gene In Bovine

Genes and makers that have a great impact on growth traits need to be found firstly forcattle molecular maker-assisted breeding. FOXA2(forkhead box A2) is an importanttranscription factor which plays central roles in the tissue development, islet secretion, liverglucose and lipid metabolism and adipose differentiation. Currently, no research about cattleFOXA2gene was reported. Therefore, we adopted the real-time quantitative PCR to detect theexpression pattern of FOXA2gene at mRNA level in different periods of Qinchuan cattle andin different nutrient densities of Chinese Holstein, searching for its potential impact on cattlegrowth. After that, this study detected variations of FOXA2gene by DNA pool sequencing,polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methodsfrom five cattle breeds at population level, including Qinchuan, Nanyang, Jiaxian Red, Denanand Xiajia breeds. And then, we analyzed the genetic diversity of the four SNPs and theirassociation relationship with the growth traits of five Chinese cattle populations, findingmolecular makers which contribute to growth and development of cattle. This study may lay ascientific foundation for further marker-assisted selection of cattle and promotion of beefcattle. Main results were shown as following:(1) Tissue expression pattern analysis of Qinchuan FOXA2gene in different stagesThe relative expression of Qinchuan FOXA2gene of nine tissues in three periods (fetalbovine, calve and adult cattle) showed that its expression was affected by the tissue specificityand temporal specificity. At a stage, FOXA2gene expressed variously among tissues. It washighly expressed in the liver of all three stages and emerged in the lung at the fetal andnewborn stages, while the intestine had a second expression at the newborn stage. Its mRNAlevel was quite low in other tissues like stomach, muscle and adipose. Meanwhile, as for thesame tissue, we compared the FOXA2gene expression quantity among the three stages,finding that it changed significantly with age in tissues, except for heart tissue. Particularly,the expression was increased with the ages in the liver, spleen, and kidney. (2) Tissue expression pattern analysis of Chinese Holstein FOXA2gene in differentnutrient levelsThe expression of Chinese Holstein FOXA2gene in seven tissues was similar with thoseof Qinchuan cattle at the newborn stage. Besides, we studyed the expression of FOXA2genein newborn Chinese Holstein within three treatments of nutrient density, and found that thelevel of nutrient could significantly affect its expression in the tissues such as heart, spleen,adipose and muscle. In the heart, liver and spleen, the FOXA2gene was expressed inaccordance with the nutrition diet. On the contrary, its mRNA level of the lower nutrition dietsgroup was markedly higher than those of the higher diets group in adipose and muscle tissues,indicating a negative correlation between the expression of FOXA2gene and nutrition level.(3) Detection and genetic analysis of FOXA2gene SNPs in five populationsIn this study, four sequence variants (SVs) of cattle FOXA2gene were screened anddetected (SV1, g.7005C>T; SV2, g.7044C>G; SV3, g.8449A>G; SV4, g.8537T>C). Thegenetic diversity index (PIC, He and Ne) revealed that all the four SNPs showed a moderatepolymorphism in most populations, indicating that FOXA2gene was comparatively rich ofpolymorphic information and had a large potential in breeding. Unexpectedly, resultsconfirmed that all four SVs were demonstrated weak linkage. According to the haplotypeanalysis, we discovered a different distribution pattern between breeds. The Jiaxian Red andQinchuan cattle were quite similar while Nanyang cattle displayed another distribution.(4) Association analysis between polymorphisms of FOXA2gene and growth traitsof three local cattle breedsAssociation analysis between four SNPs and growth traits in adulthood cattle showedthat: some growth traits of the individuals with genotype CT at SV1locus in Nanyang, Xiajiaand Denan cattle, genotype GG at SV2locus in Jiaxian Red cattle, genotype AT at SV3locusin Jiaxian Red and Xiajia cattle, genotype AA at SV3locus in Nanyang cattle, genotype TC atSV4locus in all three local breeds and Denan crossbreed were significantly better than otherindividuals (P<0.05or P<0.01). Association of the same SNP differed within breeds andgrowth traits. Besides, further association analysis of the four SNPs with growth traitsindicated that combined genotype significantly associated with important growth traits (likebody length and body weight) of Qinchuan and Jiaxian Red cattle. Association analysis forthe single locus and combined genotype of four SNPs comprehensive illustrated that thesepolymorphic loci could be used as genetic makers to raise growth trait of beef cattle andFOXA2gene was an important candidate gene for cattle breeding.