Fig. 4.

Organization of the mammary bilayer and localization of ERα-expressing cells. A Schematic representation of mammary duct and alveolus and main specific markers of the basal myoepithelial, ERα-positive and –negative luminal cell lineages. Ductal ERα^high cells express nuclear ERα as detected by IHC whereas ERα^low cells express ERα transcripts without detectable nuclear staining. Keratins (K5, K14, K8, K18); α-smooth muscle actin (α-SMA); oxytocin receptor (OXTR). B: ERα expression in ductal and alveolar structures, as revealed by IHC on PFA-fixed paraffin sections, using mouse monoclonal anti-ERα (Santa Cruz, sc-542, MC-20, described in [212]). Left: sections through a duct and a TEB (insert) from a pubertal mouse. Right: section through a group of alveoli from a pregnant mouse. Unlike ductal, alveolar luminal cells rarely display ERα nuclear expression. The arrowhead points to an ERα cell located in the stroma. Bars, 50 μm and 25 μm