microRNAs are small non-coding RNAs that are important regulators of gene expression in a range of animals, including nematodes. Scientists from the University of Glasgow have utilized microarray to analyse a cluster of four miRNAs from the pathogenic nematode species Haemonchus contortus that are closely linked in the genome. They found that the cluster is conserved only in clade V parasitic nematodes and in some ascarids, but not in other clade III species nor in clade V free-living nematodes. Members of the cluster are present in parasite excretory-secretory products and can be detected in the abomasum and draining lymph nodes of infected sheep, indicating their release in vitro and in vivo. As observed for other parasitic nematodes, H. contortus adult worms release extracellular vesicles (EV).

Small RNA libraries were prepared from vesicle-enriched and vesicle-depleted supernatants from both adult worms and L4 stage larvae. Comparison of the miRNA species in the different fractions indicated that specific miRNAs are packaged within vesicles, while others are more abundant in vesicle-depleted supernatant. Hierarchical clustering analysis indicated that the gut is the likely source of vesicle-associated miRNAs in the L4 stage, but not in the adult worm.

These findings add to the growing body of work demonstrating that miRNAs released from parasitic helminths may play an important role in host-parasite interactions.

Developmental expression of the Hco-miR-5352 cluster across the H. contortus life cycle as assessed by microarray

LC ciences

Data for sheathed L3, activated L3 (act) (exsheathed and cultured at 37°C for 24 hours), L4 stage collected 7 days p.i., adult males and females, collected at 28 days p.i. and gut tissue extracted from adult female worms.


H. Y. Gu, N. D. Marks, A. D. Winter, C. Britton , E. Devaney et. al. (2017) Conservation of a microRNA cluster in parasitic nematodes and profiling of miRNAs in excretory-secretory products and microvesicles of Haemonchus contortus PLoS Negl Trop Dis. doi: 10.1371/journal.pntd.0006056 [abstract]

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