The benzimidazoles (BZ) are a family of anthelmintics used in livestock and human parasitic nematode control. Drug metabolism is an important modulator of drug efficacy in many systems. However, there has been much less research in nematodes. Our previous work has shown that the free-living model nematode Caenorhabditis elegans and the parasite Haemonchus contortus are induced by and detoxify BZ anthelmintics by conjugation with a glucose residue. This suggests the involvement of phase II xenobiotic metabolizing enzymes, and specifically the UGT (UDP-glucuronosyltransferase) enzyme family. Furthermore, these may contribute to BZ resistance found in parasitic nematodes. The major objective of this project is to identify and functionally characterize nematode UGT enzymes that metabolize Albendazole (ABZ) in C. elegans. We undertook an RNAi screening of ugt genes and identified that knockdown of ugt-9, ugt-11 and ugt-22 make worms sensitive to albendazole (ABZ) treatment compared to wild type. However, the RNAi clones that we used of ugt-9 and ugt-11 may target other six ugt genes that are tightly liked and are closely phylogenetically related (this cluster includes ugt-9 and ugt-11, but not ugt-22). We demonstrate the redundant function of ugt-9 cluster genes in modulating ABZ potency in vivo by examining the phenotype of seven loss-of-function ugt mutants present in ugt-9 cluster. Specifically mutations in ugt-9 and ugt-11 make worms more sensitive to ABZ while ugt-13 and ugt-12 have a lesser effect. By using CRISPR-Cas-9, we made a ugt-9 cluster deficiency strain (~24 kb deletion knocking out seven of the eight ugt genes) that showed a greater sensitivity to ABZ compared to each single loss-of-function mutant. Further, ugt-9 cluster deficiency strain also showed greater sensitivity to other BZ drugs compared to wild type worms. This demonstrates that multiple ugt-9 cluster genes are involved in modulation of sensitivity to BZ.

Affiliations:
- Departments of Biochemistry & Molecular Biology, Medical Genetics, University of Calgary, Calgary, Alberta, Canada
- Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, CA
- Life Sciences Centre, UBC 2350 Health Sciences Mall Vancouver, BC, Canada