The epiphyseal region of long bone, featuring numerous bone-degrading osteoclasts (red cells). In this issue, Takayanagi and colleagues show that CaMKIV phosphorylation of CREB is essential for osteoclast maturation and function. Photo courtesy of Hiroshi Takayanagi.

Neurons positive for III-tubulin expressing tyrosine hydroxylase after serial induction and differentiation in astrocyte coculture. In this issue, Goldman and colleagues show that these neurons can induce recovery in a model of Parkinson disease, but highlight their potential to become tumorigenic. Photo courtesy of Steven Goldman.

The cover shows a transmission electron micrograph of H5N1 human influenza virus particles isolated from an infected human in Vietnam. On page 1203, de Jong and colleagues report findings from immunological and virological studies of 18 people infected with H5N1 in Vietnam. Their analysis provides clues about why H5N1 is so lethal to humans. Image courtesy of ©, NIBSC/PHOTO RESEARCHERS,INC.

Quantum-dot labeled image of the mouse kidney. In this issue, Susan Quaggin and her colleagues show that loss of the tumor suppressor VHL leads to Cxcr4 expression and glomerulonephritis (p 1081). Image courtesy of Thomas Deerinck and Mark Ellisman, University of California, San Diego.

In this issue, Gause and colleagues report the first evidence that alternatively activated macrophages are important effector cells mediating clearance of intestinal helminths. Alternatively activated macrophages have previously been implicated mainly in dampening and resolving pathology. This image shows alternatively activated macrophages (orange and yellow) surrounding invasive helminth parasite larvae in the small intestine of a mouse. Image courtesy of Robert Anthony and William Gause.

On page 835, Loukas and colleagues show that individuals resistant to schistosomal infection make immune responses to the schistosomal tetraspanin TSP2. In mice, the authors show that TSP2 is a promising antischistosomal vaccine candidate, reducing adult worm burdens and liver and fecal egg counts. The cover image shows paired adult-stage Schistosoma mansoni blood flukes. The larger male worm is carrying the female worm in his gynecophoral canal. This is a permanent state of mating and is how adult worms are usually found in vivo. Photo courtesy of Malcolm Jones, Queensland Institute of Medical Research, Australia.

Hematopoietic stem cells line the inner surface of the bone, attached by components of the extracellular matrix. On page 657, Kollet et al. show that osteoclasts, when induced to differentiate by osteoblasts, secrete various factors that cleave the extracellular matrix, resulting in the mobilization of stem cells from the bone marrow. Thus, bone homeostasis and hematopoiesis have been shown to be linked. The cover depicts a primary osteoclast stained for CXCR4 (blue), polymerized actin (red) and nuclear DNA (green).

Signaling through receptor tyrosine kinases (RTKs) can stimulate cell proliferation, and its aberrant activation is implicated in many cancers. Mig6 is an adapter protein that mitigates the response of RTKs to cellular growth factors. On page 568, Ferby et al. show that mice lacking Mig6 have a hyperactivated response to mitogens and develop tumors at high frequency, highlighting the delicate balance between promotion and suppression of RTK signaling. The cover depicts cell proliferation in cancerous gastrointestinal crypts in a Mig6-deficient mouse.

Two reports in this issue use different approaches to repair the heart using engineered tissue in rat models of myocardial infarction. On page 452, Zimmermann et al. use engineered heart tissue derived from neonatal rat heart cells, and on page 459, Miyahara et al. use sheets of mesenchymal stem cells derived from adipose tissue. The cover image is from the former study and shows the sarcomeric organization of cardiomyocytes within the graft 4 weeks after implantation (green, actin; blue, nuclei).

China wants to become a scientific powerhouse. A special News Report that starts on page 261 looks at their current progress. The cover shows the Jiayuguan Pass of the Great Wall in northwest China (Photo by China Photos/Getty Images).

Plasmodium, the parasite that causes malaria, is transmitted by a mosquito into the dermis and must reach the liver before infecting erythrocytes and causing disease. On page 220, Menard and colleagues present a realtime analysis of the fate of parasites in mice and identify a previously unrecognized step of the parasite life cycle. The image shows a scanning electron micrograph of the mosquito's proboscis. Credit: VEM / Photo Researchers, Inc

Tumors can be detected by their high metabolic rate and need for glucose. On page 122, Thomas and colleagues show that an inhibitor of cell growth can also block the expression of a crucial transcription factor that regulates glucose use in many cancer cells. The cover image shows uptake of fluorescent glucose in a tumor-bearing mouse. Original microPET image courtesy of George Thomas.