Shenzhen, China -- An international team of researchers, led by the University of Melbourne and BGI, has sequenced the draft genome of Ascaris suum, a parasitic roundworm of pig. This collaborative study, published online in the international journal Nature, provides a comprehensive resource to the scientific community and paves the way for the development of new and urgently needed interventions (drugs, vaccines and diagnostic tests) against ascariasis and other nematodiases.
Ascaris worms are soil-transmitted helminths causing ascariasis in human and animals. Human infections are commonly found in developing countries in Asia, Africa and Latin America, and favorably occurred in the tropical and sub-tropical areas with poor sanitation. Each year, more than one billion people worldwide are infected and about 135,000 are died for the diseases caused by these parasites. Parasite has been disasters to food animal producers due to the huge economic losses resulted from reduced growth and production loss of host animals.
In this study, researchers sequenced the A. suum genome at ~80-fold coverage and generated approximately 273 million base genome sequence for A. suum. The genome size is about 273 Mb and about 18,500 protein-coding genes were estimated. "Compare to the other metazoan genomes reported to date, we found this genome has few repetitive sequences, only about 4.4% of the total assembly." said Shiping Liu, the co-leading author of the study and Senior Bioinformatician of Comparative Genomics Group at BGI. "We later found out this phenomenon was probably caused by the chromatin diminution." he added.
Researchers had conducted the comparison of A. suum genome and sequences of other parasitic and free-living roundworms to understand the parasitism-related genetic factors of A. suum and its closely related species A. lumbricoides which causes human infections. In particular, many molecules and proteins identified have seemed to be involved in the invasion of host tissue and regulation with the host immune system. They predicted the secretome of A. suum to comprise 775 proteins with diverse functions and found the A. suum secretome (about 750 molecules) is rich in peptidases linked to the penetration and degradation of host tissues. Some members of the A. suum secretome may play an important role in host-tissue degradation and others are predicted to direct or evade immune responses.
"We also identified a number of potential drug targets. Notably, in the A. suum gene set, we found a homologue (acr-23) of the C. elegans monepantel receptor, suggesting that this drug may kill A. suum. By sequencing A. suum genome, we identified abundant key information to better understand the molecular biology of A. suum and the exquisite complexities of the hostparasite interactions on an immunobiological level. We believe our work will pave the way for the future Parasitic Diseases Research." said Liu.
"Each year, ascariasis affects billions of people and animals worldwide, so it is now crucial to understand its pathogenic mechanism by genomic and post-genomic approaches. In this study, we have more interesting findings, which can provide new hope for the discovery of intervention strategies, with major implications for improving global health." said Bo Li, the co-leading author of the study and Leader of Comparative Genomics Group.
|Contact: Jia Liu|