GSE65284
Loss of EZH2 results in enhanced recruitment of EZH1, Pol II and Stat5 and precocious mammary gland development
Establishment and differentiation of mammary alveoli during pregnancy are controlled by prolactin through the transcription factor STAT5. As pregnancy progresses mammary signature genes are activated in a defined temporal order, which coincides with the recruitment of STAT5 to respective regulatory sequences. This study addressed the question whether the methyltransferase and transcriptional co-activator EZH2 controls the differentiation clock of mammary epithelium. Ablation of Ezh2 from mammary stem cells resulted in precocious differentiation of alveolar epithelium and accelerated activation of mammary signature genes. This coincided with enhanced occupancy by EZH1, Pol II and STAT5 to mammary-specific loci. Notably, loss of EZH2 did not result in overt changes in genome-wide and gene-specific H3K27me3 patterns, suggesting that enhanced EZH1 recruitment can compensate for the loss of EZH2. However, differentiated mammary epithelia failed to form in the combined absence of EZH1 and EZH2. Transplantation experiments failed to demonstrate a role for EZH2 in the biology of mammary stem and progenitor cells. In summary, while EZH1 and EZH2 serve redundant functions in the establishment of H3K27me3 and formation of mammary alveoli, the presence of EZH2 is required to obtain controlled temporal differentiation of mammary epithelium. Overall design: ChIP-seq EZH1, EZH2, PolIII; WT and E2KO mammary cells