Volume 14 Issue 7, July 2011

Guided by novel structural insights, a study now demonstrates that UNC119 is a lipid-binding protein essential for proper trafficking of G-protein a subunits in mammalian photoreceptors and Caenorhabditis elegans sensory neurons.

A new study used several mouse mutants to study insulin receptor function specifically in the ventromedial nucleus of the hypothalamus (VMH), and found a role for VMH insulin signaling in promoting high-fat diet–induced obesity.

A study now shows that association of kainate receptors with the auxiliary protein Neto1 confers the slow activation and deactivation kinetics of synaptic responses, as well as the high agonist affinity seen in vivo.

Recent work suggests that the correlations between neurons are important for encoding information, but there has been significant discrepancy among studies. The authors review this rapidly growing body of literature, examine the potential sources of the discrepancies and offer guidelines for how to interpret data about neuronal correlations.

In Drosophila, larval neural circuits are remodeled during metamorphosis by both pruning and neurite remodeling, which requires TGF-β signaling. Here, Awasaki and colleagues find that glia secrete myoglianin, a TGF-β ligand, which upregulates neuronal expression of an ecdysone nuclear receptor that triggers neurite remodeling following the late-larval ecdysone peak.

Here the authors find that the kinetics of synaptic vesicle endocytosis are widely variable across different neurons and is stochastic regardless of neuronal firing histories or number of presynaptic boutons.

The authors report that light prolongs spiking during retinal waves of correlated activity that occur during mouse development by activating melanopsin-expressing intrinsically photosensitive retinal ganglion cells.

This study uses fMRI to find that visual cortical areas involved in processing task-relevant information are functionally connected with the frontal-parietal network, but those processing task-irrelevant information are simultaneously coupled with the default network. The strength of visual cortex/default network functional connectivity was predictive of subjects' abilities to suppress irrelevant information.

Because clathrin-mediated endocytosis (CME) is relatively slow, it's been suggested that a readily retrievable pool of synaptic vesicle proteins might support fast CME. The authors use a recently developed probe to monitor synaptic vesicle recycling and demonstrate the preferential recruitment of a surface pool of synaptic vesicle proteins upon stimulated endocytosis.

Huang and Trussell show that resting potential of the calyx of Held synapse is controlled by KCNQ5 potassium channels. Unlike most KCNQ channels, which activate only on depolarization, these presynaptic channels activate negative to the resting potential. These channels set the resting conductance and control release probability of the synapse.

Immediate early genes are rapidly transcribed in response to neuronal activity, but the underlying mechanism is unclear. The authors show that this rapid transcription is mediated by a stalled RNA polymerase II, poised just downstream of the transcription start site. RNAi-depletion of negative elongation factor compromises the rapid transcription.

The authors report that TACE, the tumor necrosis factor-α–converting enzyme, regulates PNS myelination by affecting neuregulin-1 type III activity. Mice lacking TACE in motor neurons show hypermyelination.

Of the three major types of ionotropic glutamate receptors, synaptic kainite receptors have slow channel kinetics. This study characterizes Neto1, a novel auxiliary subunit of kainite receptor that directly modulates ligand binding and slow kinetics of kainite receptors.

UNC119 is a protein localized to the non-motile primary cilia. Here, Zhang et al. report the crystal structure of UNC119 and provide biochemical and cellular evidence that UNC119 is a lipid-binding protein that mediates G protein trafficking. The authors also show that that UNC119 function is conserved from GPCR trafficking in C. elegans olfactory neuron to transducin trafficking in mammalian photoreceptors.

Striatal spiny neurons (SPNs) transition from a hyperpolarized 'down state' to a sustained depolarized 'up state' to regulate action selection. The authors report that glutamate uncaging on proximal dendritic spines of SPNs evokes somatic up states that track the input time course. However, glutamate uncaging on distal spines evokes up states that last hundreds of milliseconds.

This study characterizes a subset of clock neurons known as large lateral-ventral neurons and their dopaminergic/octopaminergic input circuitry in balancing light-mediated wakefulness in Drosophila.

Adding to previous findings on Drosophila pheromone cVA and its receptor Or65a in regulating male-male aggression, this study finds that prior activation Or65a-positive olfactory receptor neurons before encountering other male flies is needed to mitigate social aggression.

This study reports an anatomical and functional screen of mushroom body–extrinsic neurons in Drosophila and finds that MB-V2 cholinergic efferent neurons are essential for retrieval of aversive short- and long-term memory, but not for memory formation or consolidation. During memory retrieval, MB-V2 neurons reinforce the olfactory pathway involved in innate odor avoidance.

The authors report that insulin activates PI3K signaling in SF-1–expressing neurons of the ventromedial hypothalamus to regulate their firing frequency. Mice with insulin receptor deficiency in these neurons show protection from the metabolic effects of exposure to high-fat diet.

This paper demonstrates that orientation maps, as found in the cortex of higher mammals, are likely to arise from the spatial layout of retinal ganglion cell receptive fields in the retina. The predictions of this model are borne out in four different species.

Orientation judgments are more accurate at the horizontal and vertical orientations, possibly reflecting a statistical inference. Here the authors provide evidence for this idea, finding that observers' internal models for orientation match the local orientation distribution measured in photographs, and suggest how such information could be encoded in a neural population.

The authors record from primate dorsal anterior cingulate cortex (dACC) during a foraging task. They find that dACC neuronal responses were correlated with behavioral decisions about when to leave a depleting resource to exploit another.