ERa-binding super enhancers drive key mediators that convey uterine hormone responses

Estrogen receptor α (ERα) modulates gene expression through interactions with enhancer regions of chromatin that are frequently distal from the promoters of estrogen regulated genes. Active chromatin enriched “super-enhancer” (SE) regions, mainly described in in vitro culture systems, often control production of key cell type determining transcription factors. Here, we define ERα binding super-enhancers in vivo within hormone responsive uterine tissue. SE are already formed prior to estrogen exposure at the onset of puberty. The SE encode critical developmental factors including Rara and Hoxd. Using chromosome conformation capture with high throughput sequencing (Hi-C) we demonstrate that most ERα-binding SE are located at a chromatin loop end and most uterine genes in loop ends associated with ERα-binding SEs are estrogen regulated. Although SE are formed prior to puberty, SE-associated genes acquire optimal ERα dependent expression after reproductive maturity, indicating estrogen impacts enhancer function subsequent to assembly. ERα-binding SE-associated genes impact key uterine functions mediated by estrogen, including TGFβ and LIF signaling pathways. This is the first identification of ERα-binding SE interactions underlying hormonal regulation of genes in uterine tissue and optimal development of estrogen response Hi-C of ovariectomized adult WT uterine tissue after treatment for 1 hour with saline vehicle , estradiol, or progesterone or ERa knockout uterine tissue after treatment with saline vehicle for 1 hour