Global Expression Profiling Reveals a Role for CTGF/CCN2 in Lactogenic Differentiation of Mouse Mammary Epithelial Cells

Abstract

Mammary epithelial cells undergo a series of developmental changes during pregnancy and lactation including proliferation, differentiation, secretion and apoptosis. HC11 mouse mammary epithelial cells, which are capable of lactogen-induced differentiation in cell culture, were used to follow the changes in gene expression during this process. The expression profiles of over 20,000 genes were compared in HC11 cells undergoing lactogenic differentiation to non-differentiated cells using DNA microarray analysis. Greater than two fold changes were detected in 998 genes in the differentiated cells versus growth controls. Several genes, including CTGF/CCN2, exhibited greater than five-fold increase. Validation of the gene expression changes verified the involvement of numerous genes and pathways in the differentiation of mouse mammary epithelial cells and identified genetic pathways associated with specific transcriptional regulation. Further analysis revealed EGF-dependent regulation of a specific subset of genes including important cell cycle regulators. The expression of a subset of genes regulated by lactogenic differentiation in HC11 cells, including CTGF/CCN2 and osteopontin, was examined in mouse mammary glands revealing in vivo changes in expression during pregnancy and lactation. In addition, elevation or depletion of CTGF/CCN2 in HC11 cells had a significant effect on the degree of lactogenic differentiation observed in the cells. The studies confirm the value of expression profiling in defining transcriptional controls associated with differentiation of mammary epithelial cells and revealed novel regulators of the process, including CTGF/CCN2.