Identification of estrogen-responsive genes in the parenchyma and fat pad of the bovine mammary gland by microarray analysis

• Published in: Physiological genomics 2006-10, Vol.27 (1), p.42-53
• Main Authors: Li, Robert W, Meyer, Matthew J, Van Tassell, Curtis. P, Sonstegard, Tad S, Connor, Erin E, Van Amburgh, Michael E, Boisclair, Yves R, Capuco, Anthony V
• Format: Article
• Language: English
• Subjects: Adipose Tissue - drug effects; Adipose Tissue - metabolism; Animals; Bos taurus; Cattle - genetics; Cattle - growth & development; Cattle - metabolism; Cell Proliferation - drug effects; Epithelial Cells - cytology; Epithelial Cells - drug effects; Estradiol - pharmacology; Gene Expression - drug effects; Gene Expression Profiling; Mammary Glands, Animal - drug effects; Mammary Glands, Animal - growth & development; Mammary Glands, Animal - metabolism; Oligonucleotide Array Sequence Analysis; Ovariectomy; Reverse Transcriptase Polymerase Chain Reaction
• ISSN: 1094-8341; 1531-2267
• DOI: 10.1152/physiolgenomics.00032.2006

1 Bovine Functional Genomics Laboratory, United States Department of Agriculture-Agricultural Research Service, Beltsville, Maryland 2 Department of Animal Science, Cornell University, Ithaca, New York Identification of estrogen-responsive genes is an essential step toward understanding mechanisms of estrogen action during mammary gland development. To identify these genes, 16 prepubertal heifers were used in a 2 x 2 factorial experiment, with ovarian status (intact or ovariectomized) as the first factor and estrogen treatment as the second (control or estradiol). Heifers were ovariectomized at 4.5 mo of age, and estrogen treatments were initiated 1 mo later. After 3 days of treatment, gene expression was analyzed in the parenchyma and fat pad of the bovine mammary gland using a high-density oligonucleotide microarray. Oligonucelotide probes represented 40,808 tentative consensus sequences from TIGR Bos taurus Gene Index and 4,575 singleton expressed sequence tags derived from libraries of pooled mammary gland and gut tissues. Microarray data were analyzed by use of the SAS mixed procedure, with an experiment-wide permutation-based significance level of P < 0.1. Considerable differences in basal gene expression were noted between mammary parenchyma and fat pad. A total of 124 estrogen-responsive genes were identified, with most responding only in the parenchyma or the fat pad. The majority of genes identified were not previously reported to be estrogen responsive. These undoubtedly include genes that are regulated indirectly but also include known estrogen-targeted genes and novel genes with potential estrogen-responsive elements in their promoter regions. The distinctive expression patterns regulated by estrogen in parenchyma and fat pad shed light on the need for both tissues to obtain normal mammary development. gene expression; ovariectomy; prepubertal heifer; proliferation; tissue type