Volume 517

  • No. 7536 29 January 2015

    Perception, a ‘face built out of many lines� by Norwegian artist Espen Kluge. Squamous cell head and neck cancer is one of the most common and deadly cancers. Despite initial responses to combinations of surgery, radiation and chemotherapy, approximately half of all tumours recur, usually within two years of initial diagnosis. Molecular markers and targeted therapies have had little impact on this disease to date. Here, The Cancer Genome Atlas team presents a detailed genome-wide overview of alterations and highlights critical genetic events of potential biological and clinical significance in head and neck squamous cell carcinomas (HNSCCs) with different human papillomavirus (HPV) status. Mutational profiles reveal distinct subgroups of HNSCCs. Mutations in EGFR, FGFRs, PIK3CA and cyclin-dependent kinases represent candidate targets for therapeutic intervention in the majority of HNSCCs. Cover : www.espen-kluge.com

  • No. 7535 22 January 2015

    The Esquel pallasite � arguably the most beautiful meteorite ever discovered � consists of centimetre-scale gem-quality crystals of the silicate mineral olivine embedded in a metallic matrix of iron-nickel alloy. The pallasites are thought to originate from a ~200 km radius parent body that separated into a liquid metal core surrounded by a rocky silicate mantle shortly after the birth of the Solar System. High-resolution magnetic imaging of the iron–nickel matrix of two pallasites (Esquel and Imilac) by James Bryson et al. reveals a time-series record of magnetic activity on the pallasite parent body, encoded within nanoscale intergrowths of iron-rich and nickel-rich phases. This record captures the dying moments of the magnetic field generated as the liquid core solidified, providing evidence for a long-lasting magnetic dynamo driven by compositional convection. (Esquel image from Natural History Museum, London.)

  • No. 7534 15 January 2015

    A dragonfly, loaded with retroreflective markers, catches a fly. Primates and other vertebrates use internal models to control and predict the consequences of their movements, but invertebrates were thought to rely mostly on reflexes. In a study using motion capture to track the head and body movements of dragonflies catching flying prey, Anthony Leonardo and colleagues demonstrate a complexity of behaviour not previously seen in an insect. Approaching from below, the dragonfly’s head locks onto its target while its body manoeuvres to align to the prey’s flight path and reduce the distance to the prey. Rather than generating these steering movements reactively, by responding only to changes in prey motion, dragonflies using both reactive and predictive control. These predictions account for the motion of the prey and the dragonfly’s own body, and are consistent with generation by internal models. The experimental accessibility of the insect nervous system, combined with the load-carrying capacity of the dragonfly, opens these general principles of motor control to detailed mechanistic dissection. Cover: Igor Siwanowicz & Huai-Ti Lin.

  • No. 7533 8 January 2015

    After injury to the nervous system in the nematode Caenorhabditis elegans, an axon sprouts new growth towards its detached segment; a membrane-tethered fluorophore is shown in blue, and the cytoplasm magenta. Fragments are slightly repositioned for clarity. Massimo Hilliard and colleagues provide a detailed analysis of a highly efficient means of regeneration in the C. elegans nervous system known as axonal fusion, in which separated axon segments are able to spontaneously reconnect and fuse to restore the original circuitry. Fusion in this context prevents the breakdown of the detached axon segment and requires regeneration only to bridge the region of damage. The authors investigate the molecular machinery required for this regenerative process, and find that it begins with changes to the phospholipid composition of the axonal membrane followed by recruitment of specific molecules in the regrowing axon as well as from surrounding tissues. Remarkably, the molecules and mechanisms discovered in this process mirror those involved in the recognition and engulfment of apoptotic cells by phagocytes. Cover design by Nick Valmas, image by Casey Linton.

  • No. 7532 1 January 2015

    Dunes on Titan in a Cassini radar mapper image taken on 21 December 2008 (upper part of cover) resemble those in Conception Bay in the Namib desert, seen here from 283 km altitude in NASA crew image STS107-E-5380 (lower image). NASA’s Cassini spacecraft mission � still out there sending data from the Saturnian system � has revealed extensive aeolian (wind-formed) dunes on the surface of Titan, Saturn’s largest satellite. Devon Burr et al. used a high-pressure wind tunnel to simulate the thick near-surface atmosphere on Titan and, with numerical modelling of the low gravity and low sediment density, derived the wind speeds necessary to move dune sand on Titan. These speeds are significantly higher than those predicted by present models of sediment entrainment by wind that are based on wind-tunnel experiments under conditions relevant for Earth and Mars. Experimental results and theoretical work can be reconciled if the extremely low ratio of particle to fluid density on Titan is taken into account, a correction that is not required for high density ratio environments such as jets on comets. Cover: NASA/JPL-Caltech/ASI/ Johnson Space Center