Synthetic prions with novel strain-specified properties

Prions are infectious proteins that possess multiple self-propagating structures. The information for strains and structural specific barriers appears to be contained exclusively in the folding of the pathological isoform, PrP^Sc. Many recent studies determined that de novo prion strains could be generated in vitro from the structural conversion of recombinant (rec) prion protein (PrP) into amyloidal structures. Our aim was to elucidate the conformational diversity of pathological recPrP amyloids and their biological activities, as well as to gain novel insights in characterizing molecular events involved in mammalian prion conversion and propagation. To this end we generated infectious materials that possess different conformational structures. Our methodology for the prion conversion of recPrP required only purified rec full-length mouse (Mo) PrP and common chemicals. Neither infected brain extracts nor amplified PrP^Sc were used. Following two different in vitro protocols recMoPrP converted to amyloid fibrils without any seeding factor. Mouse hypothalamic GT1 and neuroblastoma N2a cell lines were infected with these amyloid preparations as fast screening methodology to characterize the infectious materials. Remarkably, a large number of amyloid preparations were able to induce the conformational change of endogenous PrP^C to harbor several distinctive proteinase-resistant PrP forms. One such preparation was characterized in vivo habouring a synthetic prion with novel strain specified neuropathological and biochemical properties.     

Evaluation of the fossil fish‐specific diversity in a chadian continental assemblage: Exploration of morphological continuous variation in Synodontis (Ostariophysi,Siluriformes)

In the fossil record, the quantification of continuous morphological variation has become a central issue when dealing with species identification and speciation. In this context, fossil taxa with living representatives hold great promise, because of the potential to characterise patterns of intraspecific morphological variation in extant species prior to any interpretation in the fossil record. The vast majority of catfish families fulfil this prerequisite, as most of them are represented by extant genera. However, although they constitute a major fish group in terms of distribution, and ecological and taxonomic diversity, the quantitative study of their past morphological variation has been neglected, as fossil specimens are generally identified based on the scarcest remains, that is, complete neurocrania that bear discrete characters. Consequently, a part of freshwater catfish history is unprospected and unknown. In this study, we explored the morphological continuous variation of the humeral plate shape in Synodontis catfishes using Elliptic Fourier Analysis (EFA), and compared extant members and fossil counterparts. We analysed 153 extant specimens of 11 Synodontis species present in the Chad basin, in addition to 23 fossil specimens from the Chadian fossiliferous area of Toros Menalla which is dated around 7 Ma. This highly speciose genus, which is one of the most diversified in Africa, exhibits a rich fossil record with several hundred remains mostly identified as Synodontis sp. The analysis of the outline of the humeral plate reveals that some living morphological types were already represented in the Chad Basin 7 My ago, and allows for the discovery of extinct species. Beside illuminating the complex Neogene evolutionary history of Synodontis, these results underline the interest in the ability of isolated remains to reconstruct a past dynamic history and to validate the relevance of EFA as a tool to explore specific diversity through time. J. Morphol. 277:1486–1496, 2016. © 2016 Wiley Periodicals, Inc.     

Photosynthetic Light Responses May Explain Vertical Distribution of Hymenophyllaceae Species in a Temperate Rainforest of Southern Chile

Some epiphytic Hymenophyllaceae are restricted to lower parts of the host (<60 cm; 10–100 μmol photons m^-2 s^-1) in a secondary forest of Southern Chile; other species occupy the whole host height (≥10 m; max PPFD >1000 μmol photons m^-2 s^-1). Our aim was to study the photosynthetic light responses of two Hymenophyllaceae species in relation to their contrasting distribution. We determined light tolerance of Hymenoglossum cruentum and Hymenophyllum dentatum by measuring gas exchange, PSI and PSII light energy partitioning, NPQ components, and pigment contents. H. dentatum showed lower maximum photosynthesis rates (A_max) than H. cruentum, but the former species kept its net rates (A_n) near A_max across a wide light range. In contrast, in the latter one, A_n declined at PPFDs >60 μmol photons m^-2 s^-1. H. cruentum, the shadiest plant, showed higher chlorophyll contents than H. dentatum. Differences in energy partitioning at PSI and PSII were consistent with gas exchange results. H. dentatum exhibited a higher light compensation point of the partitioning of absorbed energy between photochemical Y(PSII) and non-photochemical Y(NPQ) processes. Hence, both species allocated energy mainly toward photochemistry instead of heat dissipation at their light saturation points. Above saturation, H. cruentum had higher heat dissipation than H. dentatum. PSI yield (YPSI) remained higher in H. dentatum than H. cruentum in a wider light range. In both species, the main cause of heat dissipation at PSI was a donor side limitation. An early dynamic photo-inhibition of PSII may have caused an over reduction of the Qa⁺ pool decreasing the efficiency of electron donation to PSI. In H. dentatum, a slight increase in heat dissipation due to acceptor side limitation of PSI was observed above 300 μmol photons m^-2s^-1. Differences in photosynthetic responses to light suggest that light tolerance and species plasticity could explain their contrasting vertical distribution.     

Novel Interaction of the Z-DNA Binding Domain of Human ADAR1 with the Oncogenic c-Myc Promoter G-Quadruplex

Both G-quadruplex and Z-DNA can be formed in G-rich and repetitive sequences on genome, and their formation and biological functions are controlled by specific proteins. Z-DNA binding proteins, such as human ADAR1, have a highly conserved Z-DNA binding domain having selective affinity to Z-DNA. Here, our study identifies the Z-DNA binding domain of human ADAR1 (hZα_ADAR1) as a novel G-quadruplex binding protein that recognizes c-myc promoter G-quadruplex formed in NHEIII₁ region and represses the gene expression. An electrophoretic migration shift assay shows the binding of hZα_ADAR1 to the intramolecular c-myc promoter G-quadruplex-forming DNA oligomer. To corroborate the binding of hZα_ADAR1 to the G-quadruplex, we conducted CD and NMR chemical shift perturbation analyses. CD results indicate that hZα_ADAR1 stabilizes the parallel-stranded conformation of the c-myc G-quadruplex. The NMR chemical shift perturbation data reveal that the G-quadruplex binding region in hZα_ADAR1 was almost identical with the Z-DNA binding region. Finally, promoter assay and Western blot analysis show that hZα_ADAR1 suppresses the c-myc expression promoted by NHEIII₁ region containing the G-quadruplex-forming sequence. This finding suggests a novel function of Z-DNA binding protein as a regulator of G-quadruplex-mediated gene expression.     

Honeybee Colony Vibrational Measurements to Highlight the Brood Cycle

Insect pollination is of great importance to crop production worldwide and honey bees are amongst its chief facilitators. Because of the decline of managed colonies, the use of sensor technology is growing in popularity and it is of interest to develop new methods which can more accurately and less invasively assess honey bee colony status. Our approach is to use accelerometers to measure vibrations in order to provide information on colony activity and development. The accelerometers provide amplitude and frequency information which is recorded every three minutes and analysed for night time only. Vibrational data were validated by comparison to visual inspection data, particularly the brood development. We show a strong correlation between vibrational amplitude data and the brood cycle in the vicinity of the sensor. We have further explored the minimum data that is required, when frequency information is also included, to accurately predict the current point in the brood cycle. Such a technique should enable beekeepers to reduce the frequency with which visual inspections are required, reducing the stress this places on the colony and saving the beekeeper time.     

Certain biochemical characteristics of an insulin-like substance from the bivalve mollusk Anodonta cygnea

An insulin-like substance (ILS) was isolated from the visceral organs of the bivalve mollusc Anodonta cygnea by chromatography on a sulfocationite CU-23 and purified by reverse phase liquid chromatography. ILS was shown to be made up to several fractions with Mr ranging from 9 to 20 kDa which have identical amino acid composition but different hydrophobicity and N-terminal amino acids. It was supposed that the heterogeneity of ILS fractions is due to its genetical or posttranslational polymorphism. ILS has a low (0.02%) affinity for the mammalian insulin receptor and a low immune affinity for mammalian insulin and possesses a mitogenic activity which is commensurate with that of the epidermal growth factor. The data obtained suggest that Anodonta cygnea ILS represents a separate branch of a relatively ancient family of insulin-like hormones and growth factors responsible for metabolism and proliferation of invertebrate tissues.     

The strength of SMAD1/5 activity determines the mode of stem cell division in the developing spinal cord

The different modes of stem cell division are tightly regulated to balance growth and differentiation during organ development and homeostasis. However, the mechanisms controlling such events are not fully understood. We have developed markers that provide the single cell resolution necessary to identify the three modes of division occurring in a developing nervous system: self-expanding, self-renewing, and self-consuming. Characterizing these three modes of division during interneuron generation in the developing chick spinal cord, we demonstrated that they correlate to different levels of activity of the canonical bone morphogenetic protein effectors SMAD1/5. Functional in vivo experiments showed that the premature neuronal differentiation and changes in cell cycle parameters caused by SMAD1/5 inhibition were preceded by a reduction of self-expanding divisions in favor of self-consuming divisions. Conversely, SMAD1/5 gain of function promoted self-expanding divisions. Together, these results lead us to propose that the strength of SMAD1/5 activity dictates the mode of stem cell division during spinal interneuron generation.