Research On The Effect Of SYK On Dairy Cow Mammary Epithelial Cell Proliferation

Dairy cows are one of the most important economic animal, the milk production and milk quality is the important to economic benefits. China is the superpower dairy farming of the world, but the average annual yield of cows is lower than the world average. The rate of butterfat and milk protein content is relatively low, and it will bring serious influence for the consumption demand of consumers. Milk is synthetic and secretion by the mammary gland itself. Every mammary bubble is formed by a layer of secretory epithelial cells. These highly specialized bubble epithelial cells are the basic unit of lactation. The mammary epithelial cells will keep proliferation until early lactation, and the number of mammary epithelial cell is very important for milk yield. The expression of genes involved lactation is important to mammary gland development and lactation. Therefore, research on genes involved mammary gland development and lactation has a positive role to improve dairy cattle genetic performance and promote the development of dairy industry in China.Spleen tyrosine kinase(SYK) is a non-receptor type protein tyrosine kinase, which expresses in hematopoietic cells, fibroblasts cells, epithelial cells, liver cells, endothelial cells and mammary glands. SYK is the most important kinase in B cell signal transduction and T cell signal transduction. It play a key role in cell differentiation and proliferation. There is some research about SYK on breast cancer, but not on normal mammary gland. In order to make clear the relationship between the expression of SYK and mammary gland development and lactation, lactation dairy cow mammary gland with high or low quality milk and dry period dairy cow mammary gland were used in this research. To explore the expression and localization of SYK in dairy cow mammary gland, western blotting and laser confocal microscope were used. To research the influence of SYK on mammary epithelial cell proliferation, RNA interference and gene overexpression technology was used. In the end, the regulation mechanism of SYK on mammary epithelial cells proliferation was detected by dual luciferase reporter gene system. The results showed that SYK expression in dry period mammary gland was significant higher than lactating mammary gland. SYK was mainly located in the cytoplasm of ductal epithelial cells in dry period mammary gland. In lactating mammary gland, SYK was existed in acinar epithelial cells. When SYK was silence in mammary epithelial cells, cell proliferation decreased, as well as the expression of β-casein and signaling molecules involved in proliferation, such as AKT1 and MAPK. When SYK was overexpression, mammary epithelial cells proliferation increased. In the meanwhile, the expression of β-casein, AKT1 and MAPK increased significantly.Dual luciferase reporter gene system results showed that SYK activated AKT1 promoter activity in dairy cow mammary epithelial cells, and the activitysite is located in the AKT1 promoter region of-439~+83bp. Taken together, all these results revealed that SYK promoted mammary gland epithelial cells proliferation and differentiation. SYK gene promoted dairy cow mammary epithelial cell proliferation by regulating the transcription activity of AKT1, which was important to mammary gland reconstruction in dry period. This research provide the theoretical basis to improve the yield and quality of milk. It is important to milk industry development in China.