Screening Functional Genes Of Development And Lactation Mammary Gland In Dairy Cow

Dairy cow is an important economic animal in animal husbandry. Milk production and quality represent dairy cow cultivation level and economic benefits. In our country, average yield of dairy cow is lower than that in other countries. Besides that, milk fat percentage and the content of milk protein in milk were not able to meet the requirement of people. Milk was synthesized and secreted by mammary gland. Gene expression changes in mammary gland development and lactation is the foundation of mammary gland growth, development, differentiation, milk synthesis, secretion and transportation. So screening differentially expressed genes and identifying their functions in mammary gland development and lactation were important to improve the genetic property of dairy cow and promote the dairy industry.In lactation, milk synthesis and secretion were prosperity and coordinate regulated by most genes. In this experiment, bovine genomic gene chip of Affymetrix was used to screening differentially expressed genes in different development period of Holstein dairy cows. And gene expression profile was obtained by comparison of gene expression in virgin, pregnancy, lactation and dry period of dairy cows. At the same time, the results were verified by fluorescence quantitative RT-PCR. In this experiment, 567 differentially expressed genes were screened out by comparison of that in lactation and in virgin, pregnancy and dry period. And 163 genes were high expression and 404 genes were low expression in lactation among them. The results of fluorescence quantitative RT-PCR were identified with the results of bovine genomic gene chip. This showed that screening differentially expressed genes by gene chip was accurate and reliability.Searching differentially expressed genes in Gene Ontology database and biological annotations of these genes was obtained. The results showed that genes high expressed in lactation were correlation with physiological function in lactation closely. Genes screened in lactation mammary gland of Holstein dairy cows were mainly focus on milk synthesis and secretion. Besides that genes regulated mammary tissues development were appeared.Signal transduction analysis to differentially expressed genes obtained activated signal transduction pathway in lactation comparison to other development periods. This could explain molecular events in lactation mammary gland.In this experiment, Kcnmal and Ihh which were high expressed in lactation were selected to study the regulation function of them on lactation mammary gland of dairy cow. Gene overexpression and RNA interference were used to research Kcnmal and Ihh expression in lactation mammary epithelial cells of Holstein dairy cows respectively. Then western blot was used to detect casein and phosphorylation STAT5 expression in interfered or overexpressed lactation mammary epithelial cells. Flow cytometry was used to detect mammary epithelial cells proliferation. The results showed that Kcnmal induced casein synthesis. (p<0.05), and induced cell proliferation in lactation mammary epithelial cells (p<0.05). Ihh did not induce casein synthesis (P>0.05) and did not induce cell proliferation in lactation mammary epithelial cells (P>0.05).