Endometrial Cancer Susceptibility Gene CTCF is Essential for Progesterone Dependent Uterine Maturation
Receptors for estrogen and progesterone frequently interact, via Cohesin/CTCF loop extrusion,  at enhancers distal from regulated genes; CTCF is decreased or mutated in >20% of human endometrial tumors, indicating its importance in uterine homeostasis. To better understand how CTCF-mediated enhancer-gene interactions impact endometrial development and function, the Ctcf gene was selectively deleted in female reproductive tissues of mice. Prepubertal Ctcfd/d uterine tissue exhibited normal morphology, with a significant reduction in the number of uterine glands compared to those without Ctcf deletion (Ctcff/f mice). Post-pubertal Ctcfd/d uteri were hypoplastic with significant reduction in both the size of the endometrial stroma and number of glands. Transcriptional profiling revealed increased expression of stem cell molecules Lif, EOMES and Lgr5, and enhanced inflammation pathways following Ctcf deletion. Analysis of the response of the uterus to steroid hormone stimulation showed that the response of the uterus to estrogen was not impacted, but that CTCF deletion affects a subset of progesterone responsive genes. This finding indicates 1) mediators of P signaling remain functional following Ctcf deletion and 2) certain P regulated genes are sensitive to Ctcf deletion, suggesting they depend on gene-enhancer interactions that require CTCF. The P responsive genes altered by CTCF ablation included Ihh, Fst and Errfi1, as well as other genes involved in the regulation of critical  processes including hormone response, transcription, and inhibition of tumor generation. Overall, our findings reveal that uterine Ctcf plays a key role in P dependent expression of uterine genes underlying optimal post pubertal uterine development. Overall design: RNAseq was done