Abstract
BackgroundHookworms, infecting over one billion people, are the mostly closely related major human parasites to the model nematode Caenorhabditis elegans. Applying genomics techniques to these species, we analyzed 3,840 and 3,149 genes from Ancylostoma caninum and A. ceylanicum.ResultsTranscripts originated from libraries representing infective L3 larva, stimulated L3, arrested L3, and adults. Most genes are represented in single stages including abundant transcripts like hsp-20 in infective L3 and vit-3 in adults. Over 80% of the genes have homologs in C. elegans, and nearly 30% of these were with observable RNA interference phenotypes. Homologies were identified to nematode-specific and clade V specific gene families. To study the evolution of hookworm genes, 574 A. caninum / A. ceylanicum orthologs were identified, all of which were found to be under purifying selection with distribution ratios of nonsynonymous to synonymous amino acid substitutions similar to that reported for C. elegans / C. briggsae orthologs. The phylogenetic distance between A. caninum and A. ceylanicum is almost identical to that for C. elegans / C. briggsae.ConclusionThe genes discovered should substantially accelerate research toward better understanding of the parasites' basic biology as well as new therapies including vaccines and novel anthelmintics.
Highlights
Hookworms, infecting over one billion people, are the mostly closely related major human parasites to the model nematode Caenorhabditis elegans
Clusters ranged in size from a single expressed sequence tags (ESTs) to 203 and 323 for A. caninum and A. ceylanicum respectively (Figure 1)
Because some genes may be rapidly evolving in all nematode lineages we evaluated a subset of the trees where the difference in branch lengths between C. briggsae and C. elegans were less than one standard deviation from the mean but which had significantly different branch lengths in the two Ancylostoma species
Summary
Hookworms, infecting over one billion people, are the mostly closely related major human parasites to the model nematode Caenorhabditis elegans. Applying genomics techniques to these species, we analyzed 3,840 and 3,149 genes from Ancylostoma caninum and A. ceylanicum. Comparative sequence analysis is an approach proven to aid in recognition of genes and defining of their function, especially when comparing genomes of close evolutionary distance. Hookworms are blood-feeding nematodes that infect one billion people causing iron deficiency anemia and retarded physical and cognitive development in children [1]. The two major species infecting humans are Necator americanus and Ancylostoma duodenale. The closely related hookworm species of canids, Ancylostoma caninum, and canines and felines, A. ceylanicum, are minor parasites of humans, but are important as laboratory models for hookworm infection and disease. Sheep, seals and a variety of other mammals [2]
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