Bridging the synaptic gap: neuroligins and neurexin I in Apis mellifera

Vertebrate studies show neuroligins and neurexins are binding partners in a trans-synaptic cell adhesion complex, implicated in human autism and mental retardation disorders. Here we report a genetic analysis of homologous proteins in the honey bee. As in humans, the honeybee has five large (31-246 kb, up to 12 exons each) neuroligin genes, three of which are tightly clustered. RNA analysis of the neuroligin-3 gene reveals five alternatively spliced transcripts, generated through alternative use of exons encoding the cholinesterase-like domain. Whereas vertebrates have three neurexins the bee has just one gene named neurexin I (400 kb, 28 exons). However alternative isoforms of bee neurexin I are generated by differential use of 12 splice sites, mostly located in regions encoding LNS subdomains. Some of the splice variants of bee neurexin I resemble the vertebrate alpha- and beta-neurexins, albeit in vertebrates these forms are generated by alternative promoters. Novel splicing variations in the 3' region generate transcripts encoding alternative trans-membrane and PDZ domains. Another 3' splicing variation predicts soluble neurexin I isoforms. Neurexin I and neuroligin expression was found in brain tissue, with expression present throughout development, and in most cases significantly up-regulated in adults. Transcripts of neurexin I and one neuroligin tested were abundant in mushroom bodies, a higher order processing centre in the bee brain. We show neuroligins and neurexins comprise a highly conserved molecular system with likely similar functional roles in insects as vertebrates, and with scope in the honeybee to generate substantial functional diversity through alternative splicing. Our study provides important prerequisite data for using the bee as a model for vertebrate synaptic development.Australian National University PhD Scholarship Award to Sunita Biswas

A single supplement of a standardised bilberry (Vaccinium myrtillus L.) extract (36 % wet weight anthocyanins) modifies glycaemic response in individuals with type 2 diabetes controlled by diet and lifestyle

Peer reviewedPublisher PD

Incorporating Virtually Immersive Environments as a Collaborative Medium for Virtual Teaming

Virtually immersive environments incorporate the use of various computer modelling and simulation techniques enabling geographically dispersed virtual project teams to interact within an artificially projected three-dimensional space online. This study focused on adoption of virtually immersive technologies as a collaborative media to support virtual teaming of both graduate and undergraduate-level project management students. The data and information from this study has implications for educators using virtually immersive environments in the classroom. In this study, we specifically evaluated two key components in this paper: 1) students' level of trust and; 2) students' willingness to use the technology, along with their belief about the virtual environment's ability to extend and improve knowledge sharing in their team work environment. We learned that while students did find the environment a positive add on for working collaboratively, there were students who were neither more nor less likely to use the technology for future collaborative ventures. Most of the students who were not very positive about the environment were “fence sitters” likely indicating needs related to additional training to improve communication skills. Finally, based on the full study results we have provided basic recommendations designed to support team trust building in the system along with interpersonal trust building to facilitate knowledge transfer and better strategic us of the technology

Events leading up to the June 2015 outburst of V404 Cyg

On 2015 June 15 the burst alert telescope (BAT) on board {\em Swift} detected an X-ray outburst from the black hole transient V404 Cyg. We monitored V404 Cyg for the last 10 years with the 2-m Faulkes Telescope North in three optical bands (V, R, and i$^{'}$). We found that, one week prior to this outburst, the optical flux was 0.1--0.3 mag brighter than the quiescent orbital modulation, implying an optical precursor to the X-ray outburst. There is also a hint of a gradual optical decay (years) followed by a rise lasting two months prior to the outburst. We fortuitously obtained an optical spectrum of V404 Cyg 13 hours before the BAT trigger. This too was brighter ($\sim1\rm\,mag$) than quiescence, and showed spectral lines typical of an accretion disk, with characteristic absorption features of the donor being much weaker. No He II emission was detected, which would have been expected had the X-ray flux been substantially brightening. This, combined with the presence of intense H$\alpha$ emission, about 7 times the quiescent level, suggests that the disk entered the hot, outburst state before the X-ray outburst began. We propose that the outburst is produced by a viscous-thermal instability triggered close to the inner edge of a truncated disk. An X-ray delay of a week is consistent with the time needed to refill the inner region and hence move the inner edge of the disk inwards, allowing matter to reach the central BH, finally turning on the X-ray emission.Comment: Accepted by ApJ Letter, 7 pages, 5 figure

Fusion Protein of the Paramyxovirus SV5: Destabilizing and Stabilizing Mutants of Fusion Activation

AbstractThe fusion (F) protein of the paramyxovirus SV5 strain W3A causes syncytium formation without coexpression of the SV5 hemagglutinin-neuraminidase (HN) glycoprotein, whereas the F protein of the SV5 strain WR requires coexpression of HN for fusion activity. SV5 strains W3A and WR differ by three amino acid residues at positions 22, 443, and 516. The W3A F protein residues P22, S443, and V516 were changed to amino acids found in the WR F protein (L22, P443, and A516, respectively). Three single-mutants, three double-mutants, and the triple-mutant were constructed, expressed, and assayed for fusion using three different assays. Mutant P22L did not cause fusion under physiological conditions, but fusion was activated at elevated temperatures. Compared with the W3A F protein, mutant S443P enhanced the fusion kinetics with a faster rate and greater extent, and had a lower activation temperature. Mutant V516A had little effect on F protein-mediated fusion. The double-mutant P22L,S443P was capable of causing fusion, suggesting that the two mutations have opposing effects on fusion activation. The WR F protein requires coexpression of HN to cause fusion at 37°C, and does not cause fusion at 37°C when coexpressed with influenza virus hemagglutinin (HA); however, at elevated temperatures coexpression of WR F protein with HA resulted in fusion activation. In the crystal structure of the core trimer of the SV5 F protein (Baker, K. A., Dutch, R. E., Lamb, R.A., and Jardetzky, T. S. (1999). Mol. Cell 3, 309–319), S443 is the last residue (with interpretable electron density) in an extended chain region and the temperature factor for S443 is high, suggesting conformational flexibility at this point. Thus, the presence of prolines at residues 22 and 443 may destabilize the F protein and thereby decrease the energy required to trigger the presumptive conformational change to the fusion-active state

A Sparse Object Coding Scheme in Area V4

SummarySparse coding has long been recognized as a primary goal of image transformation in the visual system [1–4]. Sparse coding in early visual cortex is achieved by abstracting local oriented spatial frequencies [5] and by excitatory/inhibitory surround modulation [6]. Object responses are thought to be sparse at subsequent processing stages [7, 8], but neural mechanisms for higher-level sparsification are not known. Here, convergent results from macaque area V4 neural recording and simulated V4 populations trained on natural object contours suggest that sparse coding is achieved in midlevel visual cortex by emphasizing representation of acute convex and concave curvature. We studied 165 V4 neurons with a random, adaptive stimulus strategy to minimize bias and explore an unlimited range of contour shapes. V4 responses were strongly weighted toward contours containing acute convex or concave curvature. In contrast, the tuning distribution in nonsparse simulated V4 populations was strongly weighted toward low curvature. But as sparseness constraints increased, the simulated tuning distribution shifted progressively toward more acute convex and concave curvature, matching the neural recording results. These findings indicate a sparse object coding scheme in midlevel visual cortex based on uncommon but diagnostic regions of acute contour curvature

Fluid/solid transition in a hard-core system

We prove that a system of particles in the plane, interacting only with a certain hard-core constraint, undergoes a fluid/solid phase transition