Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. Earth Science News .




EPIDEMICS
Humans and chimps share genetic strategy in battle against pathogens
by Staff Writers
Chicago IL (SPX) Feb 19, 2013


Fighting off pathogens is more dynamic, a constant arms race. Balancing selection may have enabled humans and chimps to retain multiple lines of defense that can be called on when a pathogen evolves new weapons.

A genome-wide analysis searching for evidence of long-lived balancing selection-where the evolutionary process acts not to select the single best adaptation but to maintain genetic variation in a population-has uncovered at least six regions of the genome where humans and chimpanzees share the same combination of genetic variants.

The finding, to be published Feb. 14 in the journal Science, suggests that in these regions, human genetic variation dates back to a common ancestor with chimpanzees millions of years ago, before the species split. It also highlights the importance of the dynamic co-evolution of human hosts and their pathogens in maintaining genetic variation.

Balancing selection allows evolution to keep all hereditary options open. The classic human example is the persistence of two versions of the hemoglobin gene: a normal version and hemoglobin S., a mutation that distorts the shape and function of red blood cells. Those who inherit two normal hemoglobin genes are at high risk for malaria, a parasitic disease that infects more than 200 million people each year.

Those who inherit one normal gene and one hemoglobin S. gene are partially protected from malaria-a potentially life-saving benefit. Those with two copies of the gene suffer from sickle-cell anemia, a serious and lifelong circulatory disease.

"When we looked for genetic clues pointing to other, more ancient, examples of balancing selection, we found strong evidence for at least six such regions and weaker evidence for another 119-many more than we expected," said study author Molly Przeworski, PhD, professor of human genetics and of ecology and evolution at the University of Chicago.

"We don't yet know what their functions are," she said. None of the six regions codes for a protein. There are clues that they are involved in host-pathogen interactions, "but which pathogens, what immune processes," she said, "we don't know."

The researchers used genetic data from 10 chimpanzees from Western Africa and 59 humans from sub-Saharan Africa who were part of the 1,000 Genomes Project.

The scientists looked for cases in which genetic variations that arose in the ancestor of humans and chimpanzees have been maintained through both lines. The fact that variation in these regions of the genome has persisted for so long argues that they "must have been functionally important over evolutionary time," said Ellen Leffler, a graduate student in Przeworski's laboratory and first author of the study.

The researchers, from the University of Chicago and Oxford University, designed the study to be very conservative. "We wanted to find the cases we believed the most, rather than the most cases," Przeworski said.

Computers sorted snippets of the genetic data from humans and chimps into clusters depending on how similar the subjects were to each other. For almost every snippet, they found a cluster of humans and a separate cluster of chimpanzees, as expected. But there were a few segments of the genomes in which each cluster included both chimpanzees and humans; in those regions, some humans were more closely related to some chimpanzees than to other humans.

"Instances in which natural selection maintains genetic variation in a population over millions of years are thought to be extremely rare," the authors wrote. The oldest and best known example of balanced polymorphism shared between humans and chimpanzees is the major histocompatibility complex (MHC), a group of genes that help the immune system distinguish between the body and potential invaders, such as bacteria or viruses.

Last year, a team led by Przeworski found that humans and gibbons shared genetic variation related to the ABO blood-group system from a common ancestor.

The six new examples of balanced selection described in this study appear to play a role, like the MHC, in fending off infectious disease. This requires a variety of evolutionary tools, including balancing selection.

When a population moves to a new environment-for example the exodus out of Africa to northern Europe-they face many one-time adjustments, such as adapting to less intense sunlight and decreased ultraviolet radiation. Over many generations, their offspring manage to decrease melanin production-a static adaptation for a static environment.

Fighting off pathogens is more dynamic, a constant arms race. Balancing selection may have enabled humans and chimps to retain multiple lines of defense that can be called on when a pathogen evolves new weapons.

"Our results imply that dynamic co-evolution of human hosts and their pathogens has played an important role in shaping human variation," Przeworski said. "This highlights the importance of a different kind of selection pressure in human evolution."

The National Institutes of Health, The Royal Society, the Wellcome Trust and the Howard Hughes Medical Institute funded this study. Additional authors include Ziyue Gao, Laure Segurel and Guy Sella from the University of Chicago; Susanne Pfeifer, Adam Auton, Oliver Venn, Rory Bowden, Peter Donnelly and Gilean McVean from Oxford University; Ronald Bonstrop from the Biomedical Primate Research Centre in the Netherlands; and Jeffrey Wall from the University of California at San Francisco.

.


Related Links
University of Chicago Medical Center
Epidemics on Earth - Bird Flu, HIV/AIDS, Ebola






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





EPIDEMICS
Cold resistance runs in genes
Moscow (Voice of Russia) Feb 15, 2013
British researchers have found a cold resistance gene in the DNA of indigenous Siberian tribes, which helps them survive in the harsh local environment. A team of geneticists from Cambridge University took DNA samples from about 200 natives of Siberia. Laboratory tests revealed the presence of a cold-responsive gene that enhances freezing tolerance. Remarkably, it controls metabolic proces ... read more


EPIDEMICS
Four guilty of manslaughter in Italy quake trial

Warning of emergency alert system hacks

No health effects from Fukushima: Japan researcher

Aid trickles into tsunami-hit Solomons despite aftershocks

EPIDEMICS
Researchers strain to improve electrical material and it's worth it

Explosive breakthrough in research on molecular recognition

Indra Develops The First High-Resolution Passive Radar System

ORNL scientists solve mercury mystery

EPIDEMICS
Quantifying Sediment From 2011 Flood Into Louisianas Wetlands

Japanese scientists hunt for groundwater

Landslides delivered preferred upstream habitats for coho salmon

Middle East river basin has lost Dead Sea-sized quantity of water

EPIDEMICS
Ice age extinction shaped Australian plant diversity

European sat data confirms UW numbers that Arctic is on thin ice

NASA Scientists Part of Arctic Sea Ice Study

Rapid changes in Arctic ecosystem during 2012 ice minimum

EPIDEMICS
Marsh plants actively engineer their landscape

Advance promises to expand biological control of crop pests

Buffaloes a divisive link to Hong Kong's past

Mexico to slaughter a half million chickens over bird flu

EPIDEMICS
Flood research shows human habits die hard

Indonesia floods, landslides kill 17

Mystery gold gifts for tsunami-wracked Japan port

Shimmering water reveals cold volcanic vent in Antarctic waters

EPIDEMICS
South Sudan president retires over 100 army generals

Pistorius shooting puts spotlight on S.African gun violence

US warns of tensions on Sudan-S.Sudan border

Jane Goodall: chimp scientist turned activist

EPIDEMICS
Tiny mutation had big evolutionary impact

Bilingual babies get good at grammar

UF researchers include humans in most comprehensive tree of life to date

The last Neanderthals of southern Iberia did not coexist with modern humans




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement