title: Global gene expression and systems biology analysis of bovine monocyte-derived macrophages in response to in vitro challenge with Mycobacterium bovis.
abstract: BACKGROUND
  Mycobacterium bovis, the causative agent of bovine tuberculosis, is a major cause of mortality in global cattle populations. Macrophages are among the first cell types to encounter M. bovis following exposure and the response elicited by these cells is pivotal in determining the outcome of infection. Here, a functional genomics approach was undertaken to investigate global gene expression profiles in bovine monocyte-derived macrophages (MDM) purified from seven age-matched non-related females, in response to in vitro challenge with M. bovis (multiplicity of infection 2:1). Total cellular RNA was extracted from non-challenged control and M. bovis-challenged MDM for all animals at intervals of 2 hours, 6 hours and 24 hours post-challenge and prepared for global gene expression analysis using the Affymetrix® GeneChip® Bovine Genome Array.
  
  
  RESULTS
  Comparison of M. bovis-challenged MDM gene expression profiles with those from the non-challenged MDM controls at each time point identified 3,064 differentially expressed genes 2 hours post-challenge, with 4,451 and 5,267 differentially expressed genes detected at the 6 hour and 24 hour time points, respectively (adjusted P-value threshold ≤ 0.05). Notably, the number of downregulated genes exceeded the number of upregulated genes in the M. bovis-challenged MDM across all time points; however, the fold-change in expression for the upregulated genes was markedly higher than that for the downregulated genes. Systems analysis revealed enrichment for genes involved in: (1) the inflammatory response; (2) cell signalling pathways, including Toll-like receptors and intracellular pathogen recognition receptors; and (3) apoptosis.
  
  
  CONCLUSIONS
  The increased number of downregulated genes is consistent with previous studies showing that M. bovis infection is associated with the repression of host gene expression. The results also support roles for MyD88-independent signalling and intracellular PRRs in mediating the host response to M. bovis.
authors.affiliation: Animal Genomics Laboratory, UCD School of Agriculture and Food Science, University College Dublin, Belfield, Dublin, Ireland.
authors.forename: David A
authors.initials: DA
authors.lastname: Magee
authors.forename: Maria
authors.initials: M
authors.lastname: Taraktsoglou
authors.forename: Kate E
authors.initials: KE
authors.lastname: Killick
authors.forename: Nicolas C
authors.initials: NC
authors.lastname: Nalpas
authors.forename: John A
authors.initials: JA
authors.lastname: Browne
authors.forename: Stephen D E
authors.initials: SD
authors.lastname: Park
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Conlon
authors.forename: David J
authors.initials: DJ
authors.lastname: Lynn
authors.forename: Karsten
authors.initials: K
authors.lastname: Hokamp
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Gordon
authors.forename: Eamonn
authors.initials: E
authors.lastname: Gormley
authors.forename: David E
authors.initials: DE
authors.lastname: MacHugh
mesh_terms: D000818:Animals; D002417:Cattle; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D016678:Genome; D006099:Granuloma / Q000378:metabolism; D066298:In Vitro Techniques; D008264:Macrophages / Q000166:cytology / Q000382:microbiology; D009000:Monocytes / Q000166:cytology* / Q000382:microbiology; D009163:Mycobacterium bovis / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D012313:RNA / Q000378:metabolism; D015398:Signal Transduction; D049490:Systems Biology; D059467:Transcriptome; D014380:Tuberculosis, Bovine / Q000382:microbiology
chemical_list: D012313:RNA