Abstract

Adipose, mammary, and hepatic gene expression profiling in lactating cows using a bovine cDNA microarray 

J. J. Loor, N. A. Janovick, R. E. Everts, S. L. Rodriguez-Zas, H. A. Lewin, and J. K. Drackley.  University of Illinois, Urbana.

ADSA/ASAS/PSA Annual Joint Meeting, St. Louis, July 25-29, 2004

Simultaneous analysis of gene expression in four adipose depots [mesenteric (MS), omental (OM), subcutaneous (SQ), perirenal (PR)], mammary (MG), and liver (LV) of lactating cows was performed using cDNA microarray technology.  Tissues were collected at slaughter from multiparous cows around peak (50 DIM), mid (95 DIM), and late (245 DIM) lactation.  A microarray consisting of 7,872 cDNA inserts was used for transcript profiling.  Annotation was based on similarity searches using BLASTN and TBLASTX against human and mouse UniGene databases and the human genome.  Cy3- and Cy5-labelled cDNA from liver and a standard reference (derived from a mixture of cattle tissues) were used for hybridizations.  Loess-normalized log-transformed ratios (tissue/standard) were used to detect differential gene expression.  Clustering analysis of gene expression around peak lactation showed that SQ had expression patterns that differed by 57% from other tissues.  LV gene expression differed from MG and adipose by 50%; whereas expression in MG differed from adipose by 44%.  Among adipose depots, gene expression in PR differed from MS and OM by 17%.  Using Benjamini and Hochberg’s False Discovery Rate (0.05) and a global gene error model, to account for the dependence of variation on signal intensities, we detected differential expression of 355 genes across tissues.  The same 24 genes were >5-fold in SQ than LV or MG.  Some of these were associated with intracellular signaling, inflammatory responses, and apoptosis.  One gene involved in the regulation of glucose oxidation was 3-, 5-, and 20-fold greater in MS, OM, and PR, respectively, than SQ.  Thirteen genes were >5-fold in LV than MG, and 10 were >5-fold in MG than LV.  Genes with >5-fold expression in LV than other tissues included one of the mitochondrial lipid oxidation pathway and one of unknown function.  Our results reveal previously unknown tissue-specific gene expression patterns during established lactation. Journal of Dairy Science, 87(Suppl. 1):T135.