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Archive - Jun 12, 2011

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Significant Litter of Cheetah Cubs Born at Conservation Facility

Five cheetah cubs were born on May 28, 2011 to 6-year-old Amani at the Smithsonian Conservation Biology Institute in Front Royal, Virginia. Amani is a dedicated mother according to keepers, who have observed her nursing and grooming the cubs. This litter is particularly significant to the Association of Zoos and Aquariums’ Species Survival Plan for cheetahs because cheetah births in zoos across the country have dwindled. The SSP matches animals across the country to ensure genetic diversity in the population. This is the only litter of cheetahs born this year in a North American zoo. Cheetah experts recently met to discuss dramatic management changes to bolster the population, recommending that cheetahs that are genetically valuable and of reproductive age be moved to one of nine breeding centers—eight in the United States and one in Canada. This will give the animals more space and mating options, increasing the odds of successful reproduction. “We are very excited that Amani had such a large litter of cubs this time,” said Adrienne Crosier, SCBI cheetah biologist. “These cubs are very significant for the future of the population, and each birth gives us an opportunity to learn more about cheetah biology and how females raise their young.” The mortality rate for cheetah cubs in human care is 20 percent during the first six months, compared to a mortality rate of up to 70 percent in the wild population in east Africa. Keepers will continue to monitor the newborns. In addition to the litters born at SCBI in Front Royal, two litters of cheetahs have been born at the Zoo’s Washington, D.C. facility since 2004. SCBI is one of five centers participating in research to boost the captive cheetah population as part of the Conservation Centers for Species Survival, also known as C2S2.

Research Links Cell Division and Oxygen Levels

Cells grow abundantly when oxygen is available, and generally stop growing when it is scarce. Although this seems straightforward, no direct link has ever been established between the cellular machinery that senses oxygen and that which controls cell division. Now, in the June 10 issue of Molecular Cell, researchers at Johns Hopkins report that the mini-chromosome maintenance (MCM) proteins, which promote cell division, also directly control the oxygen-sensing hypoxia-inducible factor 1 (HIF-1) protein. "It's always been a mystery why a vast excess of MCM proteins is present in cells, but now we have discovered at least one reason," says Dr. Gregg Semenza, the C. Michael Armstrong Professor of Medicine, director of the vascular program in Hopkins' Institute for Cell Engineering and a member of the McKusick-Nathans Institute of Genetic Medicine. "Our data indicate that MCMs mediate crosstalk between the cell division machinery and proteins that help cells react to changes in their surroundings." Since discovering HIF-1 in the 1990s, Dr. Semenza's team has been studying how it works to sense oxygen levels and turn on genes that help cells survive when oxygen is low. To find proteins that HIF-1 physically interacts with, the team went on a biochemical fishing expedition and, using HIF-1 as bait, pulled out MCM7. MCM7 is a member of a larger group of related proteins that are known to bind to DNA and start its duplication when a cell gets ready to divide. Using a different protein-binding technique, the team then found that HIF-1 also binds to MCM3. When it senses low oxygen levels, HIF-1 turns on genes that enable cells to adapt, such as genes that stimulate the growth of new blood vessels and genes that alter a cell's metabolism to change how much oxygen it consumes for energy generation.