Transcriptome analysis of a parasitic clade V nematode: comparative analysis of potential molecular anthelmintic targets in Cylicostephanus goldi.

This study analyzes the genome of the parasite Cylicostephanus goldi, a nematode that commonly infects horses, and compares its genome to other parasites in order to identify possible targets for parasite-killing drugs.

Research Process

• The researchers began by creating a cDNA library from RNA extracted from 17 C. goldi adult parasites of both sexes.
• They then used a 454 GS FLX pyrosequencer to sequence the RNA, generating over 475,215 sequences which were assembled into 26,910 contigs (overlapping regions that can provide information on the full sequence of DNA).
• Using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases, the team annotated 27% of the transcriptome, which is the set of all RNA molecules in one cell or a population of cells.

Comparative Analysis

• For further insight, the researchers compared the C. goldi dataset with the next generation transcriptomes and genomes of other clade V nematodes.
• The results showed that Oesophagostomum dentatum and Haemonchus contortus parasite’s transcriptomes have the highest levels of sequence identity with the studied dataset (45%).

Anthelmintic Targets

• The C. goldi transcriptome was examined for genes associated with the mode of action or resistance of anthelmintics, which are drugs that expel parasitic worms from the body.
• They were able to find sequences encoding proteins associated with the three major anthelmintic classes used on horses, with the sole exception being the P-glycoprotein group.
• They performed targeted resequencing of the glutamate gated chloride channel α4 subunit (glc-3), which is one of the primary targets of the macrocyclic lactone anthelmintics, across several parasite species.

Study Implications

• This study represents the first transcriptome dataset for a parasitic organism that targets horses, allowing for a deep understanding of these parasites at a molecular level.
• Key processes and genes associated with resistance to levamisole/pyrantel and macrocyclic lactone, including the glutamate gated chloride channels, were identified.
• This novel data is expected to provide important insights for future studies on the biology of these parasites and efforts to counter anthelmintic resistance.