Microarray analysis of gene expression in blood neutrophils of parturient cows

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Abstract
It is well documented that blood neutrophils from parturient dairy cows do not perform as well as neutrophils from nonparturient cows in laboratory assays of adhesion, migration, or phagocytosis-induced respiratory burst. However, little is known about the possible molecular basis for parturition-induced changes in neutrophils. cDNA microarray analysis was used in the current study to explore parturition-induced changes in gene expression profiles in bovine blood neutrophils. Total RNA from isolated blood neutrophils of four parturient Holstein cows was obtained before, during, and after parturition, reverse transcribed into cDNA, and sequentially labeled with Cy3 or Cy5 dyes prior to paired hybridizations to 1,056 member bovine total leukocyte (BOTL-3) microarrays in a loop design. Resulting gene expression data were LOWESS normalized by array and analyzed using a mixed model approach. Results showed that expression profiles for 302 BOTL-3 genes were influenced by parturition. BLASTn analysis and preliminary clustering of affected genes by biological function indicated that the largest proportion (14%) of changed genes encode proteins critical to regulation of apoptosis. Independent confirmation of altered expression for 16 of these genes was achieved using quantitative real-time RT-PCR (Q-RT-PCR). A predominantly survival phenotype inferred from the microarray and Q-RT-PCR results was substantiated by monitoring apoptosis status of blood neutrophils from castrated male cattle cultured in the presence of sera from parturient cows. Thus our combined gene expression and apoptosis phenotyping results suggest that bovine parturition may induce prolonged survival in normally short-lived blood neutrophils.