Scientists now have a new research tool to better understand the pathogen Schistosoma mansoni, a complex and aggressive blood parasite that affects more than 90 million people in Africa, the Middle East and South America. The breakthrough is the result of work by Texas A&M University biologist Dr. Charles D. Criscione and his collaborators.
Criscione, an assistant professor of biology at Texas A&M, and a team of researchers recently published the first microsatellite-based genetic linkage map for S. mansoni, one of the main species of blood flukes that cause schistosomiasis, a debilitating and chronic illness that can damage internal organs and impair growth in children. People with such infections can develop a “potbelly” due to enlarged internal organs.
Their research, supported in part by the National Institutes of Health (NIH), is published in the online, open-access scientific journal Genome Biology (2009, Volume 10, Issue 6).
Criscione said the map will be useful in piecing together the S. mansoni genome sequence, which is in 19,000 fragments. Because it is the first genetic map for a platyhelminth species (flatworms), it will be a platform for other flatworm genomics.
“The linkage map we constructed will help assemble the genome and will serve as a useful genetic tool to help find genes that control important traits, such as drug resistance, virulence and host specificity,” he said. “It has been shown that the parasite can vary for many of these traits. Knowledge of genomic regions that affect these traits will help identify new targets for drugs and vaccines and may help identify parasite genes involved in pathology.”
Linkage mapping, which has been successfully used for mapping genes in other parasitic organisms, such as those that cause malaria, allows for the examination of the genetic basis of phenotypic traits.
“Most importantly, the genetic map of S. mansoni shows that we can now do classical genetics methods that researchers have used for years on model organisms, such as mice and fruit flies,” said Criscione, who joined the Texas A&M faculty in 2008.
The two-year project involved using two adult flukes to breed 88 second-generation progeny. When Criscione and his collaborators, which included Dr. Philip LoVerde from the University of Texas Health Science Center (UTHSC) and Dr. Timothy Anderson from the Southwest Foundation for Biomedical Research (SFBR) in San Antonio, examined the genetic information passed from parents to offspring, they were able to diagram a genetic map of the parasite’s chromosomes.
More than 200 million people in 76 countries are infected with schistosome parasites, causing a devastating health impact in these countries. Because mortality is not immediate, it can result in a heavy economic burden and a significant hindrance of production for developing countries. Despite this, Criscione said little is known about the genetics of schistosomiasis, considered by the World Health Organization as second in importance only to malaria. He hopes the map can generate new research interest in a disease that has gone largely ignored for quite some time.
“Schistosomiasis is a neglected disease, because research funding typically is low for the parasites,” Criscione explained. “The genome and the genetic map provide additional tools to help combat these pathogens. Additionally, we hope these tools will invigorate more research and funding to help combat them.”
Criscione received a bachelor’s of science in zoology from Louisiana State University (1995) and a master’s of science in biology from Southeastern Louisiana University (2000). After earning his doctorate from Oregon State University (2005), he spent three years as a postdoctoral scientist at SFBR, where he first worked with Anderson to study the molecular epidemiology and landscape genetics of parasitic roundworms in humans in Nepal.