Identification of multigene cysteine protease gene families in Haemonchus contortus and analysis of gut gene expression

SF600 Veterinary Medicine;QH301 Biology

Johnston, Stephanie Lauren ; Britton, Collette

University:University of Glasgow

Department:Institute of Infection Immunity and Inflammation

关键词: Haemonchus contortus, nematode, cysteine protease, cathepsin B, ELT-2;   

Others  :  http://theses.gla.ac.uk/3735/1/2012johnstonphd.pdf

来源: University of Glasgow

【 摘 要 】

Haemonchus contortus is a blood-feeding Strongylid parasite that is economically significant worldwide. Due to the increasing problem of anthelmintic resistance, alternative approaches are urgently required for parasitic nematode control. H. contortus cathepsin B gut cysteine proteases have received attention as potential vaccine candidates because of their proposed role in blood feeding. The increasing amount of H. contortus genome information has now enabled detailed identification and annotation of cathepsin B protease gene families. In this study H. contortus BAC 18f22 was annotated and found to encode eight tandemly arranged cysteine proteases related to the previously identified AC family, but with six novel genes identified. Annotation of supercontig and scaffold sequence identified many more members of the HmCP and GCP-7 cathepsin B families. In total this work has shown that the H. contortus genome encodes at least 41 cathepsin B protease genes, more than in other nematodes, to date. In contrast, Hc-cpr-6 is present as a single copy gene that is highly conserved in a number of species, suggesting an important conserved function. Further work examined regulation of gut gene expression in H. contortus, in particular the H. contortus ELT-2 GATA transcription factor (TF), as it has been shown to be the major TF in C. elegans controlling gut gene expression. A high throughput assay was developed and used to screen an integrated C. elegans worm strain expressing GFP in the gut and hypodermis (Ce-cpl-1::gfp) against 594 chemical compounds. Compounds were identified that specifically cause a decrease in gut GFP expression, affect larval development and show a degree of lethality. Further work on two of the compounds identified an embryonic effect, with a significant decrease in number of progeny. To conclude, this thesis identified a number of novel cathepsin B genes as well as two compounds potentially interfering with TF activity and gut gene expression which may be of use as novel anthelmintics.