DERMATOLOGY: Skin: The Smart Canvas
HMS researchers have unveiled a key mechanism that guides the coloring of mammalian skin epithelium. Writing in the Sept. 7 Cell, (from left) Lorin Weiner, Janice Brissette, Rong Han, and colleagues report that skin epithelial cells, long considered a passive canvas for melanocytes, actively recruit the pigment-producing cells by releasing specific signaling molecules. The finding, which paints an entirely new picture of skin pigmentation, explains why melanin is restricted to certain cell types and may lead to new insights into aggressive melanomas, which grow independently of epithelial signals.

HEMATOLOGY: Video Shows Birth of Platelets in Vivo
The complex process by which platelets are produced is less understood than that of other blood cells, yet problems in platelet production have a role in atherosclerosis, acute coronary events, and bleeding disorders. A collaboration between Ramesh Shivdasani (left) and Uli von Andrian, reported in the Sept. 21 Science, offers a first view of the process of platelet formation in living animals. With movies capturing the large megakaryocytes releasing platelets into the bloodstream, the study offers a definitive look at how platelets form.

MICROBIOLOGY : Mass Spec Measures Nitrogen Fixed by Bacteria
Twenty years ago, researchers discovered that the odd creature the shipworm owes its wood-eating ability to a species of bacteria living in its gills. The bacteria secrete two enzymes—one that digests the wood and another that grabs nitrogen from the atmosphere and converts it into ammonia and other compounds metabolized by the animal. But because the bacteria are so minute, no one had actually caught one in the act of grabbing and fixing nitrogen. Now, using their new mass spectrometry technique, Claude LeChene (right), Greg McMahon, and colleagues have documented not just individual bacteria in the act of fixing nitrogen, but have also shown the nitrogen-containing compounds as they are sent from the gill to other parts of the shipworm’s body. The study appears in the Sept. 14 Science.

ENERGY BALANCE: Master Signals Govern Plant Response to Range of Stresses
When things get rough for plants, they can’t simply move to a new environment. They have to adapt their own metabolism to face the challenge. Researchers have studied the stress response, uncovering genes that respond to different kinds of challenge, including darkness, drought, cold, lack of oxygen, and herbicides. But new findings from the lab of Jen Sheen (left) suggest that these diverse insults do not trigger unique responses in a plant’s cells; instead, they are integrated into a general signal of the plant’s status. In the Aug. 23 Nature, Sheen, Elena Baena-Gonzalez, and colleagues detail two protein kinases that are responsible for switching on a program of genetic change in response to many different stresses, the same class of kinase responsible for energy regulation in human cells.

METABOLISM: Quickly Digested Carbs Tied to Fatty Liver Disease
Mice who nibbled food high in quickly burned carbohydrates had twice as much fat in their livers—and on their bodies—as mice who munched on more slowly digested carbs, a new study finds. The results, which appear in the September Obesity, shed light on the rise in non-alcoholic fatty liver disease in overweight and obese children. In a follow-up to the mouse study, senior author David Ludwig and his colleagues will test the benefit of a diet based on slowly digested carbs for overweight and obese children with fatty livers.

Copyright 2007 by the President and Fellows of Harvard College