Focus | March 25, 2005


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	March 25, 2005 MOLECULAR BIOLOGY: No Other Way Out for Iron Hemochromatosis, or iron overload disease, is one of the most common genetic diseases and among the most baffling. Tissues such as liver, pancreas, and heart become packed with iron. Yet macrophages, whose job it is to store and recycle the iron from aging red blood cells, exhibit unusually low levels of the mineral. Why does iron build up in the tissues and not in the normally iron-rich macrophages? Adriana Donovan (on left), Nancy Andrews, and their colleagues may have found an answer to the decades-old conundrum. It appears that the protein ferroportin is the only mechanism mammalian cells have for exporting iron. And hemochromatosis may result from too much of this iron exporter. The findings, reported in the March Cell Metabolism, suggest new approaches to treating the disease, which currently affects one in 200 Caucasian Americans.
	INFECTIOUS DISEASE: Milestone Reached, But Campaign Against Polio Continues “The vaccine works. It is safe, effective, and potent.” On April 12, 1955, these words announced the long-awaited results of the Salk polio vaccine trials. Fifty years later, polio still holds sway over many people even as it hovers on the verge of extinction. The disease persists and spreads in unvaccinated populations in Africa. Survivors can suffer a kind of relapse known as postpolio syndrome, a condition Julie Silver and other doctors in physical medicine and rehabilitation are seeing among their patients. And the bigger public health issues remain current, such as developing safe vaccines for predicted future viral epidemics.
	DEVELOPMENTAL BIOLOGY: Stem Cell Niche Discovered in Placenta A study in mice reveals that the placenta is a temporary home for a large pool of blood-forming stem cells during fetal development. The research, led by Hanna Mikkola (shown) and Stuart Orkin, and published in the March Developmental Cell, solves a longstanding riddle about where the cells that form the hematopoietic system come from. Stem cells require special environments that allow them to grow and divide without differentiating into specific cell types. Studying how the placenta nurtures these cells may point to ways of cultivating blood stem cells for bone marrow transplants and other uses.