miR205 Regulates Mammary Gland Development and Stem Cell Self-renewal through YAP and Wnt signaling

Mammary gland development is fueled by stem cell self-renewal and differentiation. External cues from the microenvironment coupled with internal cues such as post-transcriptional regulation exerted by miRNAs regulate stem cell behavior and stem cell fate. We have identified a miR205 regulatory network required for mammary gland morphogenesis and stem cell maintenance. In the postnatal mammary gland, miR205 is predominantly expressed in the basal/stem cell enriched population. Conditional deletion of miR205 in mammary epithelial cells severely impaired stem cell self-renewal and mammary repopulating potential both in vitro and in vivo. miR205 null glands displayed significant changes in the basal population, basement membrane and stroma. NKD1 and PP2A-B56, which inhibit the Wnt signaling pathway, and AMOT, which causes YAP cytoplasmic retention and inactivation were identified as miR205 downstream effectors. Collectively these findings reveal an essential role of miR205 in mammary gland development. Overall design: WT;RosamTmG/mTmG and miR-205fl/fl;RosamTmG/mTmG cells were treated with Ad-cre and transplanted back to 3-wk-old SCID-Beige mice. Mammary epithelial cell (MECs) were isolated from pooled 40 WT;RosamTmG/mTmG cre+ and miR-205fl/fl;RosamTmG/mTmG cre+ outgrowths after 8 weeks. GFP+ basal cells (CD24+CD49fhigh) were further sorted from MECs of each group and RNA-seq were performed on WT and miR205fl/fl cre+ green basal cells to look for differentially expressed genes.

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Lu Y, Cao J, Napoli M, Xia Z, Zhao N, Creighton CJ, Li W, Chen X, Flores ER, McManus MT, Rosen JM