Mammary-Specific Gene Activation Is Defined by Progressive Recruitment of STAT5 during Pregnancy and the Establishment of H3K4me3 Marks

Abstract

Differentiation of mammary secretory epithelium during pregnancy is characterized by sequential activation of genes over several orders of magnitude. Although the transcription factor STAT5 is key to alveolar development, it is not clear to what extent it controls temporal activation of genetic programs in secretory epithelium. To uncover molecular mechanisms effecting progressive differentiation, we explored genome-wide STAT5 binding and H3K4me3 (i.e., trimethylated histone H3 at K4) marks in mammary tissues at early and midpregnancy and at parturition. STAT5 binding to genes induced during pregnancy was low in immature mammary tissue but increased with epithelial differentiation. Increased STAT5 binding was associated with the establishment of H3K4me3 marks and transcriptional activation. STAT5 binding preceded the formation of H3K4me3 marks in some mammary-specific genes. De novo STAT5 binding was also found at distal sites, indicating enhancers. Furthermore, we established an exhaustive mammary transcriptome. Through integration of RNA-seq and STAT5 and H3K4me4 ChIP-seq data, we discovered novel mammary-specific alternative promoters and genes, including noncoding RNAs. Our findings suggest that STAT5 is an early step in establishing transcription complexes on genes specifically expressed in mammary epithelium. This is the first study in an organ that links progressive chromatin occupancy of STAT5 to the acquisition of H3K4me3 marks and transcription during hormone-induced differentiation.

Trp63 is regulated by STAT5 in mammary tissue and subject to differentiation in cancer

“…GEO (http://www.ncbi.nlm.nih.gov/geo/) obtained Chip-seq (STAT5 and H3K4me3 (GSE40930 and GSE31578); PGR (GSE42887); H3K4me2 (GSE25105), and RNA-seq (GSE37646), data. ChIPseq data was reanalyzed using HOMER (http://homer.salk.edu/homer/) (Heinz et al 2010, Kang et al 2014a). …”

Cow management modulates gene expression in the mammary gland, a possible epigenetics role

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An automated analysis pipeline for a large set of ChIP-seq data: AutoChIP

“…To assess the performance of AutoChIP, the following mouse and human ChIP-seq data were downloaded and analyzed by MACS, HOMER, PeakRanger, and AutoChIP; mouse STAT5A (GSM1005189) and STAT5B (GSM100 5190) and their corresponding input (GSM1005193) in mammary gland tissues; human GATA3 (GSM1241752) and its corresponding input (GSM1241753) in MCF7 cell line; and human GATA3 (GSM1241754) and its corresponding input (GSM1241755) in T47D cell line (Adomas et al 2014;Kang et al 2014). …”