Effect of p-estrogen receptor at serine on its function and breast growth

Background: Estrogen receptor (ER) signaling plays an important role in the development and functional differentiation of breast and participates in the process of breast cancer. Activated ER can affect various aspects of the cell’s behavior, including proliferation， via modulating the expression of many downstream target genes. Phosphorylation is one of the activation pathways of ER. However, the relationship between estrogen receptor phosphorylation sites and breast development and carcinogenesis is not clear. Methods: Using Crisper-Cas9 gene editing technology, we constructed ER S309A mutant mice. Using carmine staining of mammary gland of mice at different developmental stages, we examined breast development of ER S309Amice. Using HE staining of vaginal smears of mice at the same time for 5 consecutive days, we measured the vaginal epithelial keratinocytes. Results: We established ER S309A mutant mice and observed breast defects in ER S309A mice. In addition, we observed decreased reproductive ability, estrous cycle disorder in ER S309A mice. And number of vaginal epithelial keratinocytes in the estrous cycle of ER S309A mice was decreased. Conclusion: These results suggest that phosphorylation site of ER at serine 309 is important for ER function and breast development.