Treatment of parasitic nematode infections in humans and livestock relies on a small arsenal of anthelmintic
drugs that have historically reduced parasite burdens. However, anthelmintic resistance is increasing, and little
is known about the molecular and genetic causes of resistance to most drugs. The free-living roundworm
Caenorhabditis elegans has proven to be a powerful model to identify and characterize the molecular targets of
the three major anthelmintic drug classes (i.e., benzimidazoles, macrocyclic lactones, and nicotinic
acetylcholine receptor agonists), demonstrating its value as a model to understand mechanisms of resistance
(MoR). Despite this knowledge, resistance against all anthelmintic drug classes is widespread. Thus, a new
approach to combat nematode infections is needed. Emodepside is a “resistance-breaking” anthelmintic with a
distinct mode of action (MoA) not found among commonly deployed anthelmintics. Studies in the C. elegans
laboratory-adapted strain, N2, have shown that SLO-1 is essential for emodepside sensitivity and that SLO-1
loss-of-function mutations are resistant to emodepside. Further, biochemistry showed that the drug opens
SLO-1 channels. However, variation in slo-1 has not been linked with resistance in natural populations, where
the MoR remains unknown, highlighting this critical moment to focus on emodepside resistance before it
becomes a burden. Preliminary data using C. elegans genome-wide association studies (GWAS) have shown
that additional genes, beyond slo-1, are involved in emodepside resistance across natural populations. First, to
identify genetic variation in candidate genes, I will introduce variants using CRISPR-Cas9 genome editing, use
established high-throughput assays (HTA) and competition assays to test the effects of genetic variants in each
strain and identify emodepside resistance genes. Second, gene expression patterns, drug metabolites, and
conjugates involved in the biotransformation of emodepside will be measured in the emodepside-resistant
C. elegans slo-1 deletion strain, to understand how slo-1 contributes to emodepside’s MoR. We must uncover
the xenobiotic metabolizing enzymes (XMEs) involved in modulating the biological activity and behavior of
emodepside. The proposed research provides a unique opportunity to use an integrative approach to obtain
novel data about emodepside’s MoR and encourage appropriate use of emodepside before resistance is
widespread. The proposed training plan will bridge my graduate experience in metabolomics with my interest in
host-parasite biology and genetics. Completing this research and training will aid my development as an
independent scientist and allow me to create a neglected tropical disease (NTD) research program using
integrative omics approaches. My focus will be on making discoveries to improve our understanding of parasite
biology, host-parasite interactions, and our ability to treat parasite infections.