IN THIS ISSUE . . .
March 15, 2005
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The National Institute of General Medical Sciences (NIGMS), one of the National Institutes of Health, supports all research featured in this digest. Although only the lead scientists are named, coworkers and other collaborators also contributed to the findings.
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Cool Image: Finding One Bug
A new, nanometer-sized biosensor can detect a single deadly bacterium in tainted ground beef. How? Researchers attached nanoparticles, each packed with thousands of dye molecules, to an antibody that recognizes the microbe E. coli O157:H7. When the nanoball-antibody combo comes into contact with the E. coli bacterium, it glows. Courtesy of Weihong Tan, professor of chemistry at the University of Florida in Gainesville.
Glowing image (on left):
A single bacterial cell glows brightly when it encounters nanoparticle-antibody biosensors, each packed with thousands of dye molecules.
SEM image (on right): Small, spherical clusters of nanoparticle-antibody sensors stick tightly to the surface of the large, rod-shaped E. coli O157:H7 cell in this standard electron microscopic image.
Tan home page
Enzyme Leads Double Life
Scientists have discovered that an important cellular enzyme leads a double life. Using a baker's yeast model system, University of Texas Southwestern Medical Center molecular biologist Ronald A. Butow found an entirely new function for the enzyme aconitase. In addition to making energy for the cell, this enzyme appears to guard the DNA that resides inside the cell's energy factory, the mitochondrion. Butow also found that disrupting the enzyme’s energy production didn’t keep it from shielding mitochondrial DNA from potential damage—a perfect example of cellular economy. From a health standpoint, aconitase may serve an important protective function, since mitochondrial DNA damage has been linked to aging and certain diseases.
Butow home page
Scientists Improve Stem Cell Growth Environment
Because human embryonic stem cells can form any of the 220 tissues and cell types in our bodies, they hold the potential to provide an unlimited supply of healthy cells that could replace damaged or diseased ones. Concerns about the presence of animal cells in the stem cell growth environment led developmental biologist Ren-He Xu at WiCell Research Institute and the University of Wisconsin-Madison to experiment with other materials. Xu and his team found that substituting synthetic human proteins for mouse feeder cells—a key ingredient in culturing stem cells—kept stem cells in their undifferentiated, “blank slate” state. The new recipe also reduced the labor involved in maintaining stem cells. Although other animal products are still present in the growth environment, this work marks an important step toward improving stem cell culture techniques.
"This work represents real progress in establishing the usefulness of human embryonic stem cells as a model system and defining the requirements for the growth and maintenance of these unique cells in a state of "stemness."
--Marion Zatz, director of the NIGMS Exploratory Centers for
Human Embryonic Stem Cell Research program,
which includes a grant to WiCell
Image caption: This image depicts a colony of human embryonic stem cells grown over a period of 10 months using synthetic human proteins in the growth environment. The cell nuclei are stained green, and the cell surface appears in red. Courtesy of Ren-He Xu.
This work also was supported by the National Center for Research Resources, part of NIH.
Xu home page
UW-Madison stem cell research home page
WiCell Research Institute home page
Similarities in "Wiring Diagrams" of Different Species
A major challenge of the post-genomic era has been to understand the complex molecular interactions that control cellular functions. In an important step toward understanding these interaction networks, a research team led by Trey Ideker, a bioengineer at the University of California, San Diego, created a “wiring diagram" of protein interactions in three higher organisms: yeast, worm, and fruit fly. The diagram revealed considerable overlaps in 71 different “network regions,” including those that govern protein degradation, RNA modification, cellular signaling, DNA synthesis, nuclear transport, and protein folding. Analyses like these are valuable tools for understanding cellular function and evolution, and for designing medicines that target particular disease-causing interactions.
“The approaches taken by Dr. Ideker and his research team are offering new opportunities for researchers to analyze the complex interactions between molecules inside cells. This work demonstrates the value of systems biology, which is emerging as a powerful way to understand complex biological networks.”
--John Whitmarsh, assistant director of the NIGMS
Center for Bioinformatics and Computational Biology
Image caption: These wiring diagrams show the patterns of protein interactions in the higher organisms of yeast, worm, and fruit fly. The horizontal dotted lines indicate protein similarities between species, and the thick and thinner solid lines indicate direct and indirect protein interactions within a species, respectively.
Ideker home page
Lab home page
Gene Profiles May Improve Cure Rate for Kids with Leukemia
Each year about 2,400 U.S. children—most of them toddlers—are diagnosed with acute lymphoblastic leukemia (ALL), a cancer affecting bone marrow cells that is the most common childhood cancer. Chemotherapy cures about 80 percent of these patients, but drug resistance and the lack of individualized treatments leave the rest at risk of relapse. Mary Relling, a pharmaceutical scientist at St. Jude Children’s Research Hospital, reported the identification of 124 cancer cell genes that predict resistance to chemotherapy drugs. Her research team also found that variations in two inherited genes predicted which ALL patients were at higher risk of relapse. Taking these genetic profiles into account could lead to more effective ALL treatment.
This work was supported by NIGMS through the NIH Pharmacogenetics Research Network and by the National Cancer Institute, part of NIH.
Relling home page
Medicines for You