by Sarah Webb

CDK5 plays a critical role in integrating new neurons into the adult brain

Stem cells in the hippocampus continue to produce new neurons throughout our lives. But the birth of these neurons is not enough: they have to both reach their appropriate location and integrate into the neural circuitry.

A team led by Fred Gage at the Salk Institute in La Jolla, California, has demonstrated that cells with low levels of cyclin-dependent kinase 5 (CDK5) don't home in on the appropriate location within the hippocampus. However, the loss of the homing signal doesn't keep the cells from integrating into the neural tissue around them, the researchers report in PLoS Biology. "A single gene seems to control orientation," Gage says. "We've separated the appropriate dendritic organization from the ability to make connections."

science, biology, newsby Alicia Chung1

VEGF prompts cells to get out and help

Part of the body's inherent healing response is to mobilize progenitor cells from the bone marrow to the site of injury. Rather than trying to collect and purify sufficient numbers of progenitor cells from bone marrow and blood donors, many clinicians hope to find better ways to summon the right types of cells from their natural reservoir in the bone marrow. In a recent study published in Cell Stem Cell, Sara Rankin and colleagues at Imperial College London demonstrate how naturally occurring growth factors can call different types of progenitor cells into duty1.

Charles Darwin was just 28 years old when, in 1837, he scribbled in a notebook "one species does change into another"—one of the first hints of his great theory. He'd recently returned to England after his five-year journey as a naturalist aboard the HMS Beagle. In South America, Oceania and most memorably the Galápagos Islands, he had seen signs that plant and animal species were not fixed and permanent, as had long been held true. And it was as if he had an inkling of the upheavals to come as he pored over specimens he had collected and others had sent him: finches, barnacles, beetles and much more. "Cuidado," he wrote in another notebook around that time, using the Spanish word for "careful." Evolution was a radical, even dangerous idea, and he didn't yet know enough to take it public.

science, biology, turtleThe AAAS Science and Human Rights Program is calling on scientists to volunteer skills and knowledge, working with human rights organizations that need scientific expertise and technical assistance. These organizations include national human rights institutions and United Nations Field Offices throughout the world. Life, physical, behavioral, and social scientists, as well as engineers, technicians, medical professionals, and public health practitioners are invited to join. Read more about "On-call" Scientists and the program to expand science in the service of human rights, and sign-up to volunteer. 

science, biology, snake, vertebraeSnakes, fish, chickens, and humans all begin life in much the same way. Early in their transformation from an amorphous blob of cells into a fully developed animal, growing cells pinch off into a string of identical segments destined to become individual vertebrae, which will later sprout blood vessels, peripheral nerves, and muscle. These repeated segments ensure that the rod-like spinal column can hunch, arch, and twist. The segmentation process also helps establish some key differences in the body plans of different organisms: while humans have 33 vertebrae, frogs have 10 or fewer, and snakes can have more than 300. 

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