Short Report

Lactogenic differentiation of HC11 cells is not accompanied by downregulation of AP-2 transcription factor genes

Richard Jäger^{* 1} , Leontios Pappas^{* 2} and Hubert Schorle¹

¹Institute for Pathology, Department of Developmental Pathology, University of Bonn Medical School, Sigmund-Freud-Strasse 25, 53127 Bonn, Germany

²Harvard University, Faculty of Arts and Sciences, Cambridge 02138, MA, USA

author email corresponding author email* Contributed equally

BMC Research Notes 2008, 1:29doi:10.1186/1756-0500-1-29

Published:	23 June 2008

Abstract

Background

During pregnancy the mammary epithelium undergoes a complex developmental process which culminates in the generation of the milk-secreting epithelium. Secretory epithelial cells display lactogenic differentiation which is characterized by the expression of milk protein genes, such as beta-casein or whey acidic protein (WAP). Transcription factors AP-2alpha and AP-2gamma are downregulated during lactation, and their overexpression in transgenic mice impaired the secretory differentiation of the mammary epithelium, resulting in lactation failure. To explore whether the downregulation of AP-2alpha and AP-2gamma is of functional significance for lactogenic differentiation, we analyzed the expression of the AP-2 family members during the lactogenic differentiation of HC11 mammary epithelial cells in vitro. Differentiation of HC11 cells was induced following established protocols by applying the lactogenic hormones prolactin, dexamethasone and insulin.

Findings

HC11 cells express all AP-2 family members except AP-2delta. Using RT-PCR we could not detect a downregulation of any of these genes during the lactogenic differentiation of HC11 cells in vitro. This finding was confirmed for AP-2alpha and AP-2gamma using Northern analysis. Differentiating HC11 cells displayed lower expression levels of milk protein genes than mammary glands of mid-pregnant or lactating mice.

Conclusion

The extent of lactogenic differentiation of HC11 cells in vitro is limited compared to mammary epithelium undergoing secretory differentiation in vivo. Downregulation of AP-2 transcription factor genes is not required for lactogenic differentiation of HC11 cells but may functionally be involved in aspects of lactogenic differentiation in vivo that are not reflected by the HC11 system.