Estrogen-mediated regulation of Fam3d in mouse uterus during the estrous cycle
The uterus, a female reproductive organ regulated by the sex hormones estrogen and progesterone, undergoes periodic cyclical changes. The estrous cycle refers to the reproductive cycle in non-primate mammalian females. During the mouse estrous cycle, the uterus undergoes various physiological changes as a result of dynamic hormonal changes. Accurate regulation of these changes is crucial for the establishment of a successful pregnancy. Notably, estrogen plays an important role in the regulation of the proestrus and estrus stages of the estrous cycle. Family with sequence similarity 3 (Fam3) is a cytokine-like gene family with four members: Fam3a, Fam3b, Fam3c, and Fam3d. Expression and regulation of the Fam3 family members in mouse uterine physiology remain largely unknown. Therefore, this study aimed to investigate the expression of Fam family members in the uterus during the estrous cycle and evaluate its regulation by estrogen using a mouse model. Analysis of mouse uterine RNA sequencing data revealed upregulated expression of Fam3b, Fam3c, and Fam3d during the proestrus and estrus stages. Fam3d expression was dynamically regulated during the estrous cycle, with high expression levels during the proestrus and estrus stages. To investigate whether Fam3d expression is regulated by estrogen, we administered estradiol (E2) to ovariectomized mice at different time points. Fam3d expression was highest 24 h after E2 injection, suggesting that estrogen plays a crucial role in regulating Fam3d expression. Furthermore, inhibition experiments using the estrogen receptor alpha (ERa) antagonist ICI revealed that estrogen regulates Fam3d expression through the ERa-mediated pathway. Immunofluorescence staining demonstrated that FAM3D was exclusively expressed in the luminal and glandular epithelia but not in the stroma. Additionally, FAM3D was predominantly localized in the cytoplasm, particularly in the apical region, and not in the nucleus. These findings provide valuable insights into the potential role of Fam3d in the uterus and lay the groundwork for future research on its function and significance in uterine physiology. Overall design: To study the genes that depend on the estrous cycle, we determined the estrous cycle in mice using a vaginal smear assay.