Abstract

Mammary gene expression profiling in cows fed a milk fat-depressing diet using a 13,000 oligonucleotide bovine microarray

J. J. Loor1, L. Piperova2, R. E. Everts1, S. L. Rodriguez-Zas1, J. K. Drackley1, R. A. Erdman2, and H. A. Lewin1. 1University of Illinois, Urbana; 2University of Maryland, College Park.

ADSA/ASAS/CSAS Annual Joint Meeting, Cincinnati, July 24-28, 2005

We studied the effects of a milk fat-depressing diet (MFD) on mammary global gene expression patterns. Six lactating Holstein cows were randomly assigned to control (CON) or MFD (HCO; 25% forage, 70% concentrate, 5% soybean oil) in a single reversal design for 3-wk periods. Mammary tissue was biopsied in wk 3 of each period. A 13,257 unique oligonucleotide (70-mers) array was used for transcript profiling. Annotation was based on similarity searches using BLASTN and TBLASTX against human, mouse, and bovine UniGene databases, the human genome, and the cattle TIGR database. Cy3- and Cy5-labelled cDNA from mammary and a reference standard were used for hybridizations (24 arrays). Loess-normalized log-transformed ratios were used to detect differential expression. ANOVA using a False Discovery Rate of P = 0.20 identified 2,175 differentially expressed genes. Hierarchical clustering of those genes showed that relative expression between CON and HCO differed by 60%. A total of 241 genes were downregulated >2-fold and 150 were upregulated >2-fold with HCO. Among genes associated with fatty acid metabolism 18 were downregulated and 5 were upregulated >1.5-fold with HCO. Twenty-six transcription factors were differentially expressed with 8 being downregulated and 3 upregulated >1.5-fold with HCO. Expression for SREBF1 did not differ. Results confirmed HCO downregulated (>1.5-fold) FASN and ACACA but also SCD, LPL, FABP3, ACAS2, SLC27AC, and ACSL1 among other lipogenic genes. Differentially expressed genes with HCO included 21 associated with insulin action, 24 with glucose metabolism, and 27 with cytokine action. Mammary from HCO had >3-fold downregulation for a gene encoding a novel nuclear protein responsible for normal triglyceride accumulation and induction of key lipogenic genes (PPAR’s, CEBP’s) in mice. Our data show that MFD is associated with complex changes in mammary transcript expression patterns. Journal of Dairy Science, 88(Suppl. 1):196.