Two genomes are better than one: insights into the biology of the parasitic nematode Haemonchus contortus

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Nematodes have been propelled into fame in the scientific community by the widespread use of Caenorhabditis elegans as a model organism. Investigation of this nematode has provided insights into key areas of biology, including development and apoptosis. While C. elegans is one of the most widely studied organisms in biology, other nematodes have also become interesting targets of investigation. Since the publication of the genome of C. elegans in 1998 the genomes of numerous other nematodes have been sequenced and analyzed; details of other nematode genome project can be found at WormBase. This work is now further expanded by the publication of the genome the strongylid nematode Hemonchus contortus which has been sequenced and analyzed by two independent groups. An Australian isolate was sequenced by Robin Gasser and colleagues, while James Cotton and colleagues have sequenced an inbred lab strain.

So what is so interesting about this nematode that makes it worth sequencing? In addition to being a close relative of the widely studied C. elegans, H. contortus belongs to the order Strongylida, which contains the most economically important parasites of ruminants. These parasites cost the agricultural community millions of dollars through lost revenue, as well as drug costs. Hookworms, including those that infect humans, also belong to the Strongylida order. While there exist anthelmintics able to target these parasites, resistance is a growing problem. H. contortus is the first strongylid nematode genome to be sequenced and this information will provide a basis for further investigation of the biology of this important class of parasites.

From the analysis of the genomes and developmental transcriptomes of H. contortus both groups have identified potential drug targets, as well as confirmed existing targets, which will help in the development of new anthelmintics to combat resistance. Vaccines are also a major area of investigation in the battle against these parasites and putative vaccine molecules were also identified from interrogation of this genome.

One of the reasons that C. elegans has become such a widespread model system is its amazing RNAi system which allows researchers to easily investigate the function of proteins by simply feeding the worms siRNA molecules targeting the desired genes. However, this RNAi pathway is not functional in all nematodes and RNAi studies in H. contortus have been hampered by inconsistent results. In addition to the identification of potential drug targets, these genomes have also illuminated components of the RNAi pathway in H. contortus, providing insight into why this pathway is not reliable in these worms. It is possible that this information may allow researchers to improve the effectiveness of RNAi in these worms to allow easier investigation of the biology of H. contortus.