Regulation of muc1 expression by cytokine and progesterone receptor interplay in HES, a human uterine epithelial cell line, and expression of human MUC1 during early pregnancy in a human MUC1 transgenic mouse model

Embryo implantation involves direct interaction of the blastocyst with the luminal epithelium of the uterus, a process regulated by cytokines and steroid hormones. MUC1, a transmembrane mucin expressed at the apical surface of uterine epithelia, acts as a barrier to microbial infection and enzymatic attack; however, loss of MUC1 at the implantation site is needed to permit embryo attachment and implantation. MUC1 expression is regulated by progesterone (P) and the proinflammatory cytokines, tumor necrosis factor alpha (TNFalpha) and interferon gamma (IFNgamma). TNFalpha and IFNgamma are highly expressed in uterine tissues under conditions where MUC1 expression is also high. Cytokines protect the uterine mucosal epithelium by triggering inflammatory responses which in turn stimulate the activity of various protective agents/molecules, such as MUC1. MUC1 is a protective agent against mucosal inflammation and bacterial infection. TNFalpha and IFNgamma activate MUC1 expression via their downstream transcription factors, nuclear factor kappa B (NFkappaB) and signal transducers and activator of transcription (STATs). Additionally, progesterone receptor (PR) regulates MUC1 gene expression in a PR isoform-specific fashion. This dissertation examines the hypothesis that interactions among PR isoforms (PRB and PRA) and cytokine-activated transcription factors play important roles in regulating MUC1 expression in the complex uterine environment.;The human uterine epithelial cell line, HES was used to examine the regulation of MUC1 expression by PR isoforms and cytokine-activated transcription factors. Low doses of IFNgamma and TNFalpha synergistically stimulate MUC1 promoter activity in HES cells. Low doses of cytokines enhance PRB-stimulation of MUC1 promoter activity. In contrast to PRA's inhibitory actions on PRB-stimulated MUC1 gene expression, PRA cooperates with cytokines to stimulate MUC1 promoter activity. The DNA binding domain (DBD) of the PR isoforms is required for cooperative stimulation of MUC1 promoter activity. MUC1 mRNA and protein expression is stimulated in the presence of cytokines and P in HES cells stably expressing PRB. ChIP assays revealed that efficient recruitment of NFkappaB and p300 to the MUC1 promoter enhanced MUC1 gene expression. These studies indicate that a dynamic interplay occurs among cytokine-activated transcription factors, PR isoforms and transcriptional cofactors in modulating MUC1 expression either during the embryo implantation process or in response to inflammatory stimuli. This interplay may have important consequences in normal and pathological contexts. Additionally, these studies provide an insight into understanding implantation failure and recurrent miscarriages.;MUC1 expression in humans is stimulated by P in the receptive phase, but P represses Muc1 expression in mice during the window of impantation. Therefore, the human MUC1 transgenic mouse model (MUC1.Tg) that also express endogenous murine Muc1 (non-human nomenclature) was employed to define the expression of human MUC1 during early pregnancy and at the site of embryo attachment. Unlike murine Muc1 mRNA and protein, human MUC1 expression persists at the time of implantation, albeit at reduced levels. These data indicate that differences in structural context of the genes or the transcriptional context between the human and mouse uterine epithelia may contribute to differences in MUC1/Muc1 gene expression.