Time course gene expression profiling of mouse mammary gland TEB and duct cells throughout branching morphogenesis. Mus musculus

Branching morphogenesis of the mammary gland is driven by the highly motile terminal end bud (TEB) throughout pubertal development. The stem cell enriched, proliferative TEB branches as it invades the mammary fat pad to create a complex network of ducts. The gene expression programs specific to the TEB and the differentiated duct are poorly understood. We conducted a time course analysis of gene expression in the TEB and duct throughout branching morphogenesis. Additionally, we determined the gene regulatory networks coordinated by the Co-factor of LIM domains (CLIM/LDB) transcriptional regulators and determined an essential function for CLIMs in branching morphogenesis by maintaining basal mammary epithelial stem cells and promoting cell proliferation. We used laser capture microdissection to isolate TEB and duct cells throughout branching morphogenesis. We then profiled gene expression in these cells to determine gene regulatory networks involved in branching morphogenesis, and specifically those regulated by CLIM transcriptional regulators. Overall design: Mouse mammary glands from 4, 6, 8, and 10 week old mice (early puberty through early adulthood) were used for laser capture microdissection of TEB and duct cells from WT and K14-DN-Clim transgenic mice. RNA was isolated (Qiagen) and hybridized to Affymetrix MouseGene 1.0 ST arrays. In addition, basal (CD29HiCD24+Lin-) and Luminal (CD29LoCD24+Lin-) cells were sorted and RNA collected for hybridization to Affymetrix MouseGene 1.0ST arrays.