title: Transcriptional changes in the hookworm, Ancylostoma caninum, during the transition from a free-living to a parasitic larva.
abstract: BACKGROUND
  Third-stage larvae (L3) of the canine hookworm, Ancylostoma caninum, undergo arrested development preceding transmission to a host. Many of the mRNAs up-regulated at this stage are likely to encode proteins that facilitate the transition from a free-living to a parasitic larva. The initial phase of mammalian host invasion by A. caninum L3 (herein termed "activation") can be mimicked in vitro by culturing L3 in serum-containing medium.
  
  
  RESULTS
  The mRNAs differentially transcribed between activated and non-activated L3 were identified by suppression subtractive hybridisation (SSH). The analysis of these mRNAs on a custom oligonucleotide microarray printed with the SSH expressed sequence tags (ESTs) and publicly available A. caninum ESTs (non-subtracted) yielded 602 differentially expressed mRNAs, of which the most highly represented sequences encoded members of the pathogenesis-related protein (PRP) superfamily and proteases. Comparison of these A. caninum mRNAs with those of Caenorhabditis elegans larvae exiting from developmental (dauer) arrest demonstrated unexpectedly large differences in gene ontology profiles. C. elegans dauer exiting L3 up-regulated expression of mostly intracellular molecules involved in growth and development. Such mRNAs are virtually absent from activated hookworm larvae, and instead are over-represented by mRNAs encoding extracellular proteins with putative roles in host-parasite interactions.
  
  
  CONCLUSIONS
  Although this should not invalidate C. elegans dauer exit as a model for hookworm activation, it highlights the limitations of this free-living nematode as a model organism for the transition of nematode larvae from a free-living to a parasitic state.
authors.affiliation: Helminth Biology Laboratory, Division of Infectious Diseases and Immunology, Queensland Institute of Medical Research, Herston, Queensland, Australia.
authors.forename: Bennett J D
authors.initials: BJ
authors.lastname: Datu
authors.forename: Robin B
authors.initials: RB
authors.lastname: Gasser
authors.forename: Shivashankar H
authors.initials: SH
authors.lastname: Nagaraj
authors.forename: Eng K
authors.initials: EK
authors.lastname: Ong
authors.forename: Peter
authors.initials: P
authors.lastname: O'Donoghue
authors.forename: Russell
authors.initials: R
authors.lastname: McInnes
authors.forename: Shoba
authors.initials: S
authors.lastname: Ranganathan
authors.forename: Alex
authors.initials: A
authors.lastname: Loukas
mesh_terms: D000722:Ancylostoma / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D017173:Caenorhabditis elegans; D019295:Computational Biology; D004285:Dogs; D020224:Expressed Sequence Tags; D018507:Gene Expression Regulation, Developmental; D006790:Host-Parasite Interactions; D007814:Larva / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction