Sox9 regulates cell state and activity of embryonic mouse mammary progenitor cells

Naoko Kogata,Anne Lowe,Erik Oliemuller,Beatrice A Howard,Mandy Tsang,Philip Bland

doi:10.1038/s42003-018-0215-3

Naoko Kogata, Anne Lowe + Show 4 more

Open Access

https://doi.org/10.1038/s42003-018-0215-3

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Abstract

Embryonic mammary cells are a unique population comprised of undifferentiated, highly plastic progenitor cells that create normal mammary tissues. The mammary gland continues to develop after birth from descendants of embryonic mammary cells. Here, we establish cell lines from mouse mammary organs, immediately after they formed during prenatal development, to facilitate studies of primitive mammary cells, which are difficult to isolate in sufficient quantities for use in functional experiments. We show that some lines can be induced to secrete milk, a distinguishing feature of mammary epithelial cells. Targeted deletion of Sox9, from one clone, decreases the ability to respond to lactogenic stimuli, consistent with a previously identified role for Sox9 in regulating luminal progenitor function. Sox9 ablation also leads to alterations in 3D morphology and downregulation of Zeb1, a key epithelial–mesenchymal transition regulator. Prenatal mammary cell lines are an invaluable resource to study regulation of mammary progenitor cell biology and development.

Highlights

Embryonic mammary cells are a unique population comprised of undifferentiated, highly plastic progenitor cells that create normal mammary tissues
Using CRISPR-Cas[9] genome editing, we investigate the role of Sox[9], an embryonic Sox transcription factor, which has been implicated in conferring stem cell state to differentiated postnatal mammary epithelial cells (MECs)[18], in the regulation of stem cell activity and the differentiation potential of cells formed during early stages of embryonic mammary gland development
green fluorescent protein (GFP) expression is not necessarily indicative of tissue of origin since the activity of s-SHIP promoter is variable in cell populations expanded in 2D culture. embryonic mammary progenitor cells (eMPC) clones expanded from single s-SHIP-GFP+ or single s-SHIP-GFP− cells contain both GFP+ and GFP− cells upon passage in 2D culture (Supplementary Fig. 1C)

Summary

Introduction

Embryonic mammary cells are a unique population comprised of undifferentiated, highly plastic progenitor cells that create normal mammary tissues. An important area of research in mammary gland biology is to determine the roles of genes and signalling pathways that regulate embryonic stages of mammary gland development, as many of these are relevant to processes that are deregulated in cancer[4,5] Despite their relevance to breast cancer research, the routine use of primary mid-gestation embryonic mammary cells for functional study is not currently feasible, due to the small size of the nascent organ. Mammary buds grow relatively slowly in size until E14 when the epithelial cells within the bud start to proliferate extensively and invade into the underlying mesenchymal tissues[6] These early stages of development are of particular interest as the cells have a number of unique properties. Our findings highlight the distinct biological features and context-dependent regulation of embryonic mammary progenitor cells and are a novel resource for studying this unique cell population

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