IN THIS ISSUE .
January 21, 2009
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Just as paleontologists have fossils and archeologists have relics, biomedical researchers have DNA to help them study the past and better understand the present. Studying changes as well as similarities in DNA sequences reveals how organisms change, or evolve, over time. In this issue, we highlight how the concept of evolution undergirds our understanding of antibiotic resistance, the rise of certain diseases and the way genes are regulated. We also join the worldwide celebration of the 200th birthday of Charles Darwin, whose work paved the way for so much of today's biomedical research. Image courtesy of science illustrator Emily Harrington of the University of California, Santa Cruz.
Just like us, chimps have opposable thumbs, recognize themselves in the mirror and live socially. They also share 96 percent of our DNA. A big difference, though, is that they don't get diseases like AIDS or most cancers. University of California, San Diego biologist Ajit Varki wondered whether evolutionary changes protect chimps against these human diseases. Varki focused on a sugar molecule called "Gc" that is made naturally by chimps but not humans. He found that many of us have antibodies against Gc, which our bodies absorb through Gc-rich foods like red meat and milk. Varki suspects that the antibodies spur an immune reaction that triggers disease.
Learn more about evolution and medical research in the upcoming issue of Findings magazine. Subscribe now to ensure you receive this special edition when it is released in late February.
Varki lab (no longer available)
Article abstract (from the December 2, 2008, issue of PNAS)
Skip the breakfast eggs, bean salad or burger enough times, and you may start to feel sluggish. This is a tell-tale sign of iron deficiency, the world's leading nutritional disorder. To start to understand how our bodies respond to this need, as well as to gain insights into diabetes, biochemist Dennis Thiele of the Duke University Medical Center turned to one of our distant cousins—yeast. He found that when the iron supply is low, yeast shut down energy-making processes that depend on iron and use a less efficient pathway involving glucose. This metabolic reshuffling could extend to us, since most primary metabolic pathways are conserved at the molecular level from yeast to humans.
NIH's National Institute of Diabetes and Digestive Kidney Diseases also supported this work.
A naturally occurring genetic "smart bomb" might help slow the spread of antibiotic-resistant bacteria. That's a recent conclusion by Northwestern University molecular biologists Erik Sontheimer and Luciano Marraffini. The "bomb" is a piece of DNA called CRISPR. Found in many microbes, CRISPR is able to recognize and destroy the genetic machinery that bacteria use to store and share drug resistance genes. Scientists might be able to harness its activity to thwart the rise of drug resistance among bacteria that cause tuberculosis, anthrax, cholera, plague and hospital-acquired infections like MRSA.
Sontheimer lab (no longer available)
Article abstract (from the December 19, 2008, issue of Science)
MicroRNAs, the tiny bits of RNA that help control gene activity, were first discovered in 1993, but it turns out that they've been around for a long time. Molecular biologist David Bartel and Andrew Grimson of the Whitehead Institute have discovered evidence of microRNAs and their relatives, piRNAs, in primitive animals that diverged from the more complex bilaterians hundreds of millions of years ago. The microRNA sequences displayed extensive diversity between animal types, suggesting different functions in each lineage. The findings show that small RNAs were present early in animal evolution and suggest that the molecules played a role in shaping the development of more complex organisms.