Methods to drive systems biology forward

The development of new methodologies has driven the expansion of systems biology over the past decades. Technological breakthroughs in sequencing, in quantitative proteomics, in single‐cell measurements, to name only a few, have each opened up whole new fields of research. To highlight the importance of new experimental and computational methodologies in enabling novel biological discoveries, we are pleased to announce the introduction of a new Methods section in Molecular Systems Biology ( http://msb.embopress.org/authorguide#methodsguide ).     

Climate change may drive cave spiders to extinction

Subterranean ecosystems present ideal opportunities to study mechanisms underlying responses to changes in climate because species within them are often adapted to a largely constant temperature. We have characterized the thermal conditions of caves in the western Alps, and related these hypogean climate data to the occurrence of Troglohyphantes spiders (Araneae, Linyphiidae). Our data indicated that present distributions reflect Pleistocene glaciation events and also pointed to specific responses as a consequence of changes in temperature. Constant temperatures recorded inside caves provide an approximation of the mean annual temperature outside, thus we extended the results to a regional scale. We used ecological niche modeling to predict habitat suitability both in the Pleistocene and under future global warming scenarios. These analyses pointed toward a future decline in habitat suitability for subterranean spiders and the potential extinction of the most restricted endemic species. When compared with other species that live in confined habitats such as islands and mountains, we expect cave species to be as much, if not more, vulnerable to climate change.     

RalB mobilizes the exocyst to drive cell migration

The Ras family GTPases RalA and RalB have been defined as central components of the regulatory machinery supporting tumor initiation and progression. Although it is known that Ral proteins mediate oncogenic Ras signaling and physically and functionally interact with vesicle trafficking machinery, their mechanistic contribution to oncogenic transformation is unknown. Here, we have directly evaluated the relative contribution of Ral proteins and Ral effector pathways to cell motility and directional migration. Through loss-of-function analysis, we find that RalA is not limiting for cell migration in normal mammalian epithelial cells. In contrast, RalB and the Sec6/8 complex or exocyst, an immediate downstream Ral effector complex, are required for vectorial cell motility. RalB expression is required for promoting both exocyst assembly and localization to the leading edge of moving cells. We propose that RalB regulation of exocyst function is required for the coordinated delivery of secretory vesicles to the sites of dynamic plasma membrane expansion that specify directional movement.     

Mathematical biology of learning to drive an automobile

In learning to drive, an individual must learn to rapidly make small corrective turns to the right or to the left as the car comes too close correspondingly to the left or to the right edges of the lane. The magnitude of the corrective turn depends on the angle at which the edge is approached. Thus, the individual must learn to produce a quantitatively correct response (corrective turn) to any one of an infinite number of possible stimuli (angles of approach). By making a number of highly oversimplifying assumptions, the problem can be reduced to a learning situation, studied previously by H. D. Landahl (Bull. Math. Biophysic,3, 13–26, 71–77, 1941). This is used not so much to obtain any relation that might be considered practically applicable immediately as toillustrate what kind of relation can be obtained from such considerations. It is shown how the safe speed of a driver depends on his total driving experience (total distance driven) as well as on his psychophysical parameters.