Navigation Links
DNA to the defense

A team of scientists headed by Dr. Sara Melville at the University of Cambridge has shown that the parasite known to cause African sleeping sickness has evolved an unusual chromosomal structure as a result of environmental adaptation. In this parasite, the chromosomes are highly enriched in subtelomeric sequences ?dynamic and variable regions that connect the chromosome ends to the gene-rich cores. These subtelomeres, in some cases comprising 75% of the total chromosome length, contain a large repertoire of genes involved in circumventing the human immune response. This finding challenges scientists' general view of how a chromosome is functionally organized. An article describing the research will appear online this week in the journal Genome Research.

African sleeping sickness, or trypanosomiasis, is caused by a protozoan parasite known as Trypanosoma brucei. Endemic to sub-Saharan Africa, it is transmitted by tsetse flies and infects a variety of mammals, including humans. There are no vaccines against T. brucei, and most drugs to treat the disease have dangerous side effects or are scarce in the countries most heavily afflicted. Each day, the disease kills approximately 100 people.

In order to avoid destruction by mammalian immune systems, T. brucei continually changes the expression of the proteins on its outer surface. These proteins are encoded by VSGs, or variant surface glycoprotein genes. While the immune system attacks most of the parasites in a given host, some trypanosomes rapidly evolve and express new variants of VSG, thereby allowing the parasite to persist and spread through a population.

In the current study, Sergio Callejas, a Marie Curie Research Fellow in Melville's laboratory and the first author on the manuscript, conducted a series of experiments to demonstrate that T. brucei has used a strategy of chromosomal expansion to diversify its repertoire of VSG genes. M ost of these genes are concentrated in subtelomeric regions, which in T. brucei, are hemizygous: only one copy of this region is present in the chromosome. In contrast, the gene-rich cores of T. brucei chromosomes are diploid, meaning that the standard two copies are present.

"The main observation from our work is that subtelomeres can dominate a chromosome to such an extent that a very small proportion of a chromosome is truly diploid," Melville explains. "These huge subtelomeres are largely non-coding DNA, yet they contain 'contingency genes' that the parasite multiplies and diversifies for future use."

In previous studies, Melville's group showed that trypanosome chromosomes were quite variable in size. "The range of size variation we observe in African trypanosomes far exceeds anything reported in other organisms to date," Melville says. "This, coupled with the potential size of the VSG repertoire in these huge subtelomeres suggests an unrivalled capacity for new immune-resistant strains of African trypanosomes."

Analysis of the genome sequence of T. brucei was published just last year, amid increasing calls for research into new control strategies for this neglected disease. The current study underscores this parasite's reputation as a master of adaptation, devoting unprecedented resources to avoiding immune attack. Since the VSG coat appears to prevent access to other non-variable parasite proteins, such capacity for variation further dims hopes for an effective vaccine for affected populations in rural Africa.


'"/>

Source:Cold Spring Harbor Laboratory


Related biology news :

1. Discovery could be key to bioterrorism defense
2. Energy management in cells may hold key to cancer defense
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:6/14/2017)... PARIS , June 15, 2017  IBM (NYSE: IBM ... the international tech event dedicated to developing collaboration between startups ... on June 15-17. During the event, nine startups will ... deliver value in various industries. ... in the international market, with a 30 percent increase in ...
(Date:5/16/2017)...   Bridge Patient Portal , an enterprise ... EMR Systems , an electronic medical record solutions ... established a partnership to build an interface between ... Centricity™ products, including Centricity Practice Solution (CPS), Centricity ... new integrations will allow healthcare delivery networks using ...
(Date:4/19/2017)... ALBANY, New York , April 19, 2017 /PRNewswire/ ... highly competitive, as its vendor landscape is marked by ... in the market is however held by five major ... and Safran. Together these companies accounted for nearly 61% ... majority of the leading companies in the global military ...
Breaking Biology News(10 mins):
(Date:10/11/2017)... ... October 11, 2017 , ... Disappearing forests and increased ... of over 5.5 million people each year. Especially those living in larger cities are ... - based in one of the most pollution-affected countries globally - decided to take ...
(Date:10/10/2017)... ... October 10, 2017 , ... For the second ... a US2020 STEM Mentoring Award. Representatives of the FirstHand program travelled to Washington, ... from US2020. , US2020’s mission is to change the trajectory of STEM education ...
(Date:10/10/2017)... ... October 10, 2017 , ... ... 13 prestigious awards honoring scientists who have made outstanding contributions ... scheduled symposium during Pittcon 2018, the world’s leading conference and exposition for laboratory ...
(Date:10/9/2017)... San Antonio, Texas (PRWEB) , ... ... ... a new study published on October 5, 2017, in the medical journal, ... demonstrated equivalence with the gold standard, video EEG, in detecting generalized tonic-clonic ...
Breaking Biology Technology: