Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2012
Publication Date: 4/23/2012
Citation: Jenkins, M.C., Obrien, C.N., Macarisin, D., Miska, K.B., Fetterer, R.H., Fayer, R. 2012. Analysis of Giardin expression during encystation of Giardia lamblia. Journal of Parasitology. DOI: 10.1645/GE-2970.1. Interpretive Summary: Giardiasis is a diarrheal disease of humans and animals caused by the protozoan Giardia lamblia. The infectious stage of the parasite, termed the cyst, is excreted by infected individuals, and is a frequent contaminant of surface waters in many countries. Our research is directed at developing therapies against giardiasis by studying how the parasite develops from the intestinal form (trophozoite stage) to cysts. The present study analyzed the production of important molecules, named giardins, that comprise the ventral disk structure of the parasite. The ventral disk enables Giardia trophozoites to adhere to cells lining the host intestine. This study showed that genes coding for giardin proteins are regulated in different ways by the two major forms of the parasite- trophozoites and cysts. This information may be useful in developing therapies against giardiasis by inhibiting production of giardin proteins during parasite development.
Technical Abstract: The present study analyzed giardin transcription in trophozoites and cysts during encystation of Giardia lamblia. Encystment was induced using standard methods, and the number of trophozoites and cysts were counted at various time-points during encystation. At all time points, RNA from both stages were assayed for levels of alpha2-, beta-, and delta-giardin mRNA as well as cyst wall protein 3 (CWP3) mRNA using quantitative RT-PCR. In encystation medium, the number of G. lamblia trophozoites decreased while the number of cysts increased between 0 and 72 hr. In trophozoites, alpha2-giardin transcription decreased over time, while beta- and delta-giardin and CWP3 transcription exhibited a slight increase at 8 hr followed by a decrease at subsequent time points. Expression of alpha2-, beta-, and delta-giardin increased at 48 hr in cysts, followed by decreased expression at 72 hr. Expression of CWP3 transcript gradually decreased from 24-72 hr in cysts. These findings represent the first analysis of giardin transcription in separate populations of trophozoites and cysts during encystation, and indicate differential regulation of beta- and delta giardin mRNA expression by these developmental stages.