title: Expression of hepatitis B virus surface antigens induces defective gonad phenotypes in Caenorhabditis elegans.
abstract: OBJECTIVE
  To test whether a simple animal,Caenorhabditis elegans(C. elegans), can be used as an alternative model to study the interaction between hepatitis B virus antigens (HBsAg) and host factors.
  
  
  METHODS
  Three plasmids that were able to express the large, middle and small forms of HBsAgs (LHBsAg, MHBsAg, and SHBsAg, respectively) driven by a ubiquitous promoter (fib-1) and three that were able to express SHBsAg driven by different tissue-specific promoters were constructed and microinjected into worms. The brood size, egg-laying rate, and gonad development of transgenic worms were analyzed using microscopy. Levels of mRNA related to endoplasmic reticulum stress,enpl-1,hsp-4,pdi-3andxbp-1, were determined using reverse transcription polymerase reaction (RT-PCRs) in three lines of transgenic worms and dithiothreitol (DTT)-treated wild-type worms.
  
  
  RESULTS
  Severe defects in egg-laying, decreases in brood size, and gonad retardation were observed in transgenic worms expressing SHBsAg whereas moderate defects were observed in transgenic worms expressing LHBsAg and MHBsAg. RT-PCR analysis revealed thatenpl-1,hsp-4andpdi-3transcripts were significantly elevated in worms expressing LHBsAg and MHBsAg and in wild-type worms pretreated with DTT. By contrast, onlypdi-3was increased in worms expressing SHBsAg. To further determine which tissue expressing SHBsAg could induce gonad retardation, we substituted thefib-1promoter with three tissue-specific promoters (myo-2for the pharynx,est-1for the intestines andmec-7for the neurons) and generated corresponding transgenic animals. Moderate defective phenotypes were observed in worms expressing SHBsAg in the pharynx and intestines but not in worms expressing SHBsAg in the neurons, suggesting that the secreted SHBsAg may trigger a cross-talk signal between the digestive track and the gonad resulting in defective phenotypes.
  
  
  CONCLUSIONS
  Ectopic expression of three forms of HBsAg that causes recognizable phenotypes in transgenic worms suggests thatC. eleganscan be used as an alternative model for studying virus-host interactions because the resulting phenotype is easily detected through microscopy.
authors.affiliation: Yi-Yin Chen, Li-Wei Lee, Szecheng J Lo, Department of Biomedical Science, College of Medicine, Chang Gung University, Tao Yuan 333, Taiwan.
authors.forename: Yi-Yin
authors.initials: YY
authors.lastname: Chen
authors.affiliation: Yi-Yin Chen, Li-Wei Lee, Szecheng J Lo, Department of Biomedical Science, College of Medicine, Chang Gung University, Tao Yuan 333, Taiwan.
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Lee
authors.affiliation: Yi-Yin Chen, Li-Wei Lee, Szecheng J Lo, Department of Biomedical Science, College of Medicine, Chang Gung University, Tao Yuan 333, Taiwan.
authors.forename: Wei-Ning
authors.initials: WN
authors.lastname: Hong
authors.affiliation: Yi-Yin Chen, Li-Wei Lee, Szecheng J Lo, Department of Biomedical Science, College of Medicine, Chang Gung University, Tao Yuan 333, Taiwan.
authors.forename: Szecheng J
authors.initials: SJ
authors.lastname: Lo
keywords: Caenorhabditis elegans; Endoplasmic reticulum stress; Gonad retardation; Green fluorescence proteins; Hepatitis B virus; Surface antigens