Processing bodies (p-bodies) are a prototypical phase-separated RNA-containing granule. Their abundance is highly dynamic and has been linked to translation. Yet, the molecular mechanisms responsible for coordinate control of the two processes are unclear. Here, we uncover key roles for eEF2 kinase (eEF2K) in the control of ribosome availability and p-body abundance. eEF2K acts on a sole known substrate, eEF2, to inhibit translation. We find that the eEF2K agonist nelfinavir abolishes p-bodies in sensory neurons and impairs translation. To probe the latter, we used cryo-electron microscopy. Nelfinavir stabilizes vacant 80S ribosomes. They contain SERBP1 in place of mRNA and eEF2 in the acceptor site. Phosphorylated eEF2 associates with inactive ribosomes that resist splitting in vitro. Collectively, the data suggest that eEF2K defines a population of inactive ribosomes resistant to recycling and protected from degradation. Thus, eEF2K activity is central to both p-body abundance and ribosome availability in sensory neurons.

Human memory appears to be fragile and unpredictable. Free recall of random lists of words is a standard paradigm used to probe episodic memory. We proposed an associative search process that can be reduced to a deterministic walk on random graphs defined by the structure of memory representations. The corresponding graph model can be solved analytically, resulting in a novel parameter-free prediction for the average number of memory items recalled (R) out of M items in memory: R=sqrt[3πM/2]. This prediction was verified with a specially designed experimental protocol combining large-scale crowd-sourced free recall and recognition experiments with randomly assembled lists of words or common facts. Our results show that human memory can be described by universal laws derived from first principles.

Predictive remapping (PRE )—the ability of cells in retinotopic brain structures to transiently exhibit spatiotemporal shifts beyond the spatial extent of their classical anatomical receptive fields—has been proposed as a primary mechanism that stabilizes an organism’s percept of the visual world around the time of a saccadic eye movement. Despite the well-documented effects of PRE , a biologically plausible mathematical framework that specifies a fundamental law and the functional neural architecture that actively mediates this ubiquitous phenomenon does not exist. We introduce the Newtonian model of PRE , where each modular component of PRE manifests as three temporally overlapping forces: centripetal ( fC ), convergent ( fP ), and translational ( fT ), that perturb retinotopic cells from their equilibrium extent. The resultant and transient influences of these forces fC + fP + fT gives rise to a neuronal force field that governs the spatiotemporal dynamics of PRE . This neuronal force field fundamentally obeys an inverse-distance law PRE ∝ 1 r1.6 , akin to Newton’s law of universal gravitation [I. Newton, Newton’s Principia: The Mathematical Principles of Natural Philosophy (Geo. P. Putnam, New-York, 1850)] and activates retinotopic elastic fields elϕ’s. We posit that elϕ’s are transient functional neural structures that are self-generated by visual systems during active vision and approximate the sloppiness (or degrees of spatial freedom) within which receptive fields are allowed to shift, while ensuring that retinotopic organization does not collapse. The predictions of this general model are borne out by the spatiotemporal changes in visual sensitivity to probe stimuli in human subjects around the time of an eye movement and qualitatively match neural sensitivity signatures associated with predictive shifts in the receptive fields of cells in premotor and higher-order retinotopic brain structures. The introduction of this general model opens the search for possible biophysical implementations and provides experimentalists with a simple, elegant, yet powerful mathematical framework they can now use to generate experimentally testable predictions across a range of biological systems.

Mitochondria continuously change their shape and thereby influence different cellular processes like cell death or development. Recently, we showed that during starvation mitochondria fuse into a highly connected network. The change in mitochondrial shape was dependent on inactivation of the fission protein Drp1, through targeting of two different phosphorylation sites. This rapid inhibition of mitochondrial fission led to unopposed fusion, protecting mitochondria from starvation-induced degradation and enabling the cell to survive nutrient scarce conditions.

PURPOSE: To discover proteins that have the potential to contribute to the tight packing of fiber cells in the lens.

METHODS: Crude fiber cell membranes were isolated from ovine lens cortex. Proteins were separated by two-dimensional gel electrophoresis, and selected protein spots identified by micro-sequencing. The identification of galectin-3 was confirmed by immunoblotting with a specific antibody. The association of galectin-3 with the fiber cell plasma membrane was investigated using immunofluorescence microscopy, solubilization trials with selected reagents, and immunoprecipitation to identify candidate ligands.

RESULTS: A cluster of three protein spots with an apparent molecular weight of 31,000 and isoelectric points ranging between 7 and 8.5 were resolved and identified as galectin-3. This protein was associated peripherally with the fiber cell plasma membrane and interacted with MP20, an abundant intrinsic membrane protein that had been identified previously as a component of membrane junctions between fiber cells.

CONCLUSIONS: The detection of galectin-3 in the lens is a novel result and adds to the growing list of lens proteins with adhesive properties. Its location at the fiber cell membrane and its association with the junction-forming MP20 is consistent with a potential role in the development or maintenance of the tightly packed lens tissue architecture.

We demonstrate gas cluster ion beam scanning electron microscopy (SEM), in which wide-area ion milling is performed on a series of thick tissue sections. This three-dimensional electron microscopy technique acquires datasets with <10 nm isotropic resolution of each section, and these can then be stitched together to span the sectioned volume. Incorporating gas cluster ion beam SEM into existing single-beam and multibeam SEM workflows should be straightforward, increasing reliability while improving z resolution by a factor of three or more.

Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) generates 3D datasets optimally suited for segmentation of cell ultrastructure and automated connectome tracing but is limited to small fields of view and is therefore incompatible with the new generation of ultrafast multibeam SEMs. In contrast, section-based techniques are multibeam-compatible but are limited in z-resolution making automatic segmentation of cellular ultrastructure difficult. Here we demonstrate a novel 3D electron microscopy technique, Gas Cluster Ion Beam SEM (GCIB-SEM), in which top-down, wide-area ion milling is performed on a series of thick sections, acquiring < 10 nm isotropic datasets of each which are then stitched together to span the full sectioned volume. Based on our results, incorporating GCIB-SEM into existing single beam and multibeam SEM workflows should be straightforward and should dramatically increase reliability while simultaneously improving z-resolution by a factor of 3 or more.

The brainstem contains several neuronal populations, heterogeneous in term of neurotransmitter/neuropeptide content, which are important for controlling various aspects of the REM phase of sleep. Among these populations are the Calbindin (Calb)-immunoreactive NPCalb neurons, located in the Nucleus papilio, within the dorsal paragigantocellular nucleus (DPGi), and recently shown to control eye movement during the REM phase of sleep. We performed in depth data-mining of the in-situ hybridization data collected at the Allen Brain Atlas, in order to identify potentially interesting genes expressed in this brainstem nucleus. Our attention focused on genes encoding neuropeptides, including Cart (Cocaine and Amphetamine Regulated Transcripts) and Nesfatin1. While Nesfatin1 appeared ubiquitously expressed in this Calb-positive neuronal population, Cart was co-expressed in only a subset of these glutamatergic NPCalb neurons. Furthermore, a REM sleep deprivation and rebound assay performed with mice revealed that the Cart-positive neuronal population within the DPGi was activated during REM sleep (as measured by c-fos immunoreactivity), suggesting a role of this neuropeptide in regulating some aspects of REM sleep. The assembled information could afford functional clues to investigators, conducive to further experimental pursuits.

Examination of the genetic differences between aphids that can transmit citrus tristeza virus, CTV, and those which cannot, may lead to a greater understanding of the virus-aphid interactions necessitating virus acquisition and transmission. Since a cDNA library had been completed the previous year for the brown citrus aphid, a vector of CTV, a second aphid cDNA library was made to a non-CTV aphid vector, the pea aphid, Acyrthosiphon pisum. Comparisons between these two genetic datasets will provide a better understanding of the dynamics of aphid feeding, digestion, development, and may elucidate elements related to virus interactions that were previously unknown. Identification of the numerous proteins actively involved in feeding and digestion from aphids will provide specific targets for the development of new methods of control aimed at disrupting aphid feeding and ultimately reducing the acquisition and transmission of plant viruses which cause disease.

The pea aphid, Acyrthosiphon pisum, exhibits several environmentally cued, discrete, alternate phenotypes (polyphenisms) during its life cycle. In the wing polyphenism, female progeny develop as either winged or unwinged depending on the extent of crowding or host plant quality experienced by the mother. Males also have the ability to develop as either winged or unwinged, but this is genetically determined by a single locus on the X chromosome and is thus referred to as a wing polymorphism. In order to gain insight into the patterns of gene expression that underlie the wing polyphenism and polymorphism we have used a pea aphid cDNA microarray to examine gene expression in winged and unwinged females and males. Results suggest that winged and unwinged morphs exhibit systemic differences in gene expression and that many of these differences are shared between the wing polyphenism and polymorphism (i.e., between females and males). In addition, adult winged and unwinged males exhibit pronounced differences when compared to adult females and fourth instar males, as well as to each other.