The mitochondrial calcium uniporter is a highly selective ion channel

During intracellular Ca2+ signalling mitochondria accumulate significant amounts of Ca2+ from the cytosol. Mitochondrial Ca2+ uptake controls the rate of energy production, shapes the amplitude and spatio-temporal patterns of intracellular Ca2+ signals, and is instrumental to cell death. This Ca2+ uptake is undertaken by the mitochondrial Ca2+ uniporter (MCU) located in the organelle's inner membrane. The uniporter passes Ca2+ down the electrochemical gradient maintained across this membrane without direct coupling to ATP hydrolysis or transport of other ions. Carriers are characterized by turnover numbers that are typically 1,000-fold lower than ion channels, and until now it has been unclear whether the MCU is a carrier or a channel. By patch-clamping the inner mitochondrial membrane, we identified a previously unknown Ca2+-selective ion channel sensitive to inhibitors of mitochondrial Ca2+ uptake. Our data indicate that this unique channel binds Ca2+ with extremely high affinity (dissociation constant < or =2 nM), enabling high Ca2+ selectivity despite relatively low cytoplasmic Ca2+ concentrations. The channel is inwardly rectifying, making it especially effective for Ca2+ uptake into energized mitochondria. Thus, we conclude that the properties of the current mediated by this novel channel are those of the MCU.     

Enhanced partner preference in a promiscuous species by manipulating the expression of a single gene

The molecular mechanisms underlying the evolution of complex behaviour are poorly understood. The mammalian genus Microtus provides an excellent model for investigating the evolution of social behaviour. Prairie voles (Microtus ochrogaster) exhibit a monogamous social structure in nature, whereas closely related meadow voles (Microtus pennsylvanicus) are solitary and polygamous. In male prairie voles, both vasopressin and dopamine act in the ventral forebrain to regulate selective affiliation between adult mates, known as pair bond formation, as assessed by partner preference in the laboratory. The vasopressin V1a receptor (V1aR) is expressed at higher levels in the ventral forebrain of monogamous than in promiscuous vole species, whereas dopamine receptor distribution is relatively conserved between species. Here we substantially increase partner preference formation in the socially promiscuous meadow vole by using viral vector V1aR gene transfer into the ventral forebrain. We show that a change in the expression of a single gene in the larger context of pre-existing genetic and neural circuits can profoundly alter social behaviour, providing a potential molecular mechanism for the rapid evolution of complex social behaviour.     

Trail geometry gives polarity to ant foraging networks

Pheromone trails are used by many ants to guide foragers between nest and food. But how does a forager that has become displaced from a trail know which way to go on rejoining the trail? A laden forager, for example, should walk towards the nest. Polarized trails would enable ants to choose the appropriate direction, thereby saving time and reducing predation risk. However, previous research has found no evidence that ants can detect polarity from the pheromone trail alone. Pharaoh's ants (Monomorium pharaonis) produce elaborate trail networks throughout their foraging environment. Here we show that by using information from the geometry of trail bifurcations within this network, foragers joining a trail can adaptively reorientate themselves if they initially walk in the wrong direction. The frequency of correct reorientations is maximized when the trail bifurcation angle is approximately 60 degrees, as found in natural networks. These are the first data to demonstrate how ant trails can themselves provide polarity information. They also demonstrate previously unsuspected sophistication in the organization and information content of networks in insect societies.