Optimizing Nervous System-Specific Gene Targeting with Cre Driver Lines: Prevalence of Germline Recombination and Influencing Factors.

The Cre-loxP system is invaluable for spatial and temporal control of gene knockout, knockin, and reporter expression in the mouse nervous system. However, we report varying probabilities of unexpected germline recombination in distinct Cre driver lines designed for nervous system-specific recombination. Selective maternal or paternal germline recombination is showcased with sample Cre lines. Collated data reveal germline recombination in over half of 64 commonly used Cre driver lines, in most cases with a parental sex bias related to Cre expression in sperm or oocytes. Slight differences among Cre driver lines utilizing common transcriptional control elements affect germline recombination rates. Specific target loci demonstrated differential recombination; thus, reporters are not reliable proxies for another locus of interest. Similar principles apply to other recombinase systems and other genetically targeted organisms. We hereby draw attention to the prevalence of germline recombination and provide guidelines to inform future research for the neuroscience and broader molecular genetics communities

Lineage and Functional Analyses of Specific Subsets of Retinal Progenitor Cells

The vertebrate central nervous system (CNS) is made up of a diverse array of cell types. The retina, an accessible part of the CNS with seven major cell types and more than sixty cell subtypes, is an excellent model system to study cell fate determination in the CNS. Previous retroviral lineage tracing experiments have demonstrated that retinal progenitor cells (RPCs) are multipotent, and give rise to clones of variable sizes and cell type compositions. Two models are proposed to explain this variability in clone size and composition: One model states that there are different subsets of RPCs, whose distinctive molecular profiles determine their daughter cell fates, while the other model argues that RPCs are equipotent and daughter cell types are determined by environmental cues and/or stochastic cellular processes. To test the hypothesis on distinct RPCs, we first asked whether we could identify specific RPC subsets that would produce specific daughter cell types. We made use of 10 molecular markers to mark specific RPC subsets, and traced individual subsets' daughter cell fates with Cre-recombinase fate mapping and retroviral lineage tracing. A novel RPC subset, which express the basic helix-loop-helix (bHLH) transcription factor Ngn2, were found to be heavily biased towards generating rod photoreceptors and amacrine cells in terminal divisions in the postnatal mouse retina. Next, we partitioned the postnatal RPC pool into different RPC subsets with molecular marker Ngn2 and Olig2, and probed individual subsets' responsiveness to misexpression of two sets of transcription factors, which are known to play important roles in retinal cell fate determination. We have shown that different RPC subsets respond differently to the same genetic perturbation, which is indicative of their distinctive intrinsic capabilities to generate certain daughter cell types. Together, we have shown that in the mouse retina, the RPC pool is composed of distinct RPC subsets, each of which have unique molecular profiles, give rise to specific daughter cell types, and respond differently to perturbations. This study provides new insight into cell fate determination in the retina, and may shed light on a more general mechanism of cell fate determination in a variety of systems.Medical Science

Molten volcanic ash deposition in jet engines

Figure 1. (a) A schematic of the experimental setup for capturing initial formation of molten volcanic ash layer under plasma spray conditions. (b) Roughness-deposition rate relationship for EB-PVD TBCs, APS TBCs and alumina substrate under different distance to nozzle, (c) The morphology of splats onto various substrates. Safe air travel activity requires clean flight corridors. But in earth’s atmosphere, volcanic ash is undoubtedly the major source to contaminate airspace by volcanic activity and thus present critical risks to aviation safety. A Jet engine is the central part to dominate the highest level of aviation safety but also the most vulnerable part by volcanic ash. The nature of volcanic ash damage to jet engines is the molten ash deposition on the hot-section airfoils in jet engines. These ash deposits can lead to the premature failure of the components in hot-section airfoils due to heat accumulation and, more importantly, can attack the protective ceramic thermal barrier coatings (TBCs). In a real jet engine, if few of the volcanic ash particles can adhere to the surface of hot-section airfoils and form an initial molten volcanic ash deposition layer, large ash deposition nodules (several cubic centimeters in volume) can quickly build up. Therefore, the formation of initial volcanic ash deposition layer plays a key role to mitigate the its detrimental effects on jet engines. However, constraining the initial formation process of volcanic ash deposition layer in jet engines is currently unknown due to harsh operation condition. Here, we present the formation process of initial volcanic ash deposition layer by applying the atmospheric plasma thermal spray technology to stimulate the ‘in-flame generation’ volcanic ash particles (from the 2010 eruption of Eyjafjallajökull volcano due to its potential hazard for current aircraft safety) with high-energy (e.g., temperature 1833 ºC ≤ 2828 ºC; velocity 146 m s-1 ≤ 325 m s-1; and particles size ≤ 62 µm) to imping onto a solid substrate (Fig.1a). Subsequently, we quantitatively compared adhesive ability (i.e., deposition rate) of volcanic ash particles onto three categories of substrates (including traditional APS YSZ TBC, EB-PVD YSZ TBC and alumina substrate) under its increasing distance (50 ≤ 125 mm) to nozzle. Finally, we analysed the formation mechanism of initial volcanic ash deposition layer. Our results demonstrate substrate characteristics (e.g., roughness, Ra) and impact particle properties (represented by Reynold number) directly affect the adhesive ability of volcanic ash particle and subsequent layer formation. The deposition rate of volcanic ash particles decreased exponentially with increasing the distance with nozzle for all of substrates and also linearly decreasing with increasing the substrate surface roughness, Ra at each same distance to nozzle (Fig.1b). These observations indicate that volume density of particles and substrate surface roughness dramatically enhance the deposition rate of volcanic ash particles under plasma conditions. In addition, the final morphology of splats deposited by volcanic ash particles onto the different substrates were changed from disk-like to splash-like as decreased in roughness (Fig.1c). Overall, these observations and models offer important insights into the initial formation of molten volcanic ash layer for the tailoring of next-generation APS and EB-PVD TBCs that will be required to resist attack by volcanic ash in future higher-temperature jet engines

Photochemical Activation of Electrospun In₂O₃ Nanofibers for High-Performance Electronic Devices

Electrospun metal oxide nanofibers have been regarded as promising blocks for large-area, low-cost, and one-dimensional electronic devices. However, the electronic devices based on electrospun nanofibers usually suffer from poor performance and inferior viability. Here, we report an efficient photochemical process using UV light generated by a high-pressure mercury lamp to promote the electrical performance of the nanofiber-based electronic devices. Such UV treatment can lead to strong photochemical activation of electrospun nanofibers, and therefore, a stable adherent nanofiber network and electronic-clean interface were formed. By use of UV treatment, high-performance indium oxide (In₂O₃) nanofiber based field-effect transistors (FETs) with highly efficient modulation of electrical characteristics have been successfully fabricated. To reduce the operating voltage and further improve the device performance, the In₂O₃ nanofiber FETs based on solution-processed high-k AlO_<i>x</i> dielectrics were integrated and investigated. The as-fabricated In₂O₃/AlO_<i>x</i> FETs exhibit superior electrical performance, including a high mobility of 19.8 cm² V^–1 s^–1, a large on/off current ratio of 10⁶, and high stability over time and cycling. The improved performance of the UV-treated FETs was further confirmed by the integration of the electrospun In₂O₃/AlO_<i>x</i> FETs into inverters. This work presents an important advance toward the practical applications of electrospun nanofibers for functional electronic devices

Taxon-specific effects of seasonal variation and water connectivity on the diversity of phytoplankton, zooplankton and benthic organisms in urban wetland

AbstractClimate change and human activities have altered the water environment and affected the community structure of aquatic organisms. Few studies have focused on the specific responses of multiple aquatic organisms, and their interactions, to environmental factors, particularly in urban wetland ecosystems. To address this gap, this study aimed to investigate the effects of seasonal variation and water connectivity on water properties and aquatic organisms in the Xixi wetland in Zhejiang Province, China. The results demonstrated that water properties showed significant differences with changes in the season and water connectivity, and the species richness, Shannon-Wiener index, Simpson diversity and Pielou evenness of aquatic organisms varied seasonally in riverways and ponds. Meanwhile, the response of various organisms to environmental factors was inconsistent. Dissolved oxygen and suspended solids greatly influenced phytoplankton, while water temperature was the principal factor affecting the diversity of zooplankton and benthic organisms. The partial least squares path model revealed that water properties had a significant direct positive effect on the diversity of the phytoplankton community, while it had a distinct direct negative effect on zooplankton community. Environmental factors influenced the diversity of benthic organisms through a trade-off way: directly through a significant negative effect on the benthic organisms, and through a significant positive effect on the phytoplankton, further influencing the benthic community in a significantly positive way. This study highlights the understanding of the patterns and underlying mechanisms of freshwater aquatic biodiversity, and the interaction of phytoplankton, zooplankton and benthic organisms to water environmental factors in freshwater ecosystems

Crystal Orientation Behavior and Shape-Memory Performance of Poly(vinylidene fluoride)/Acrylic Copolymer Blends

The crystal orientation behavior and shape-memory performance of miscible poly(vinylidene fluoride) (PVDF)/acrylic copolymer blends in various ratios have been investigated. With the incorporation of amorphous acrylic copolymer into the gallery of PVDF lamellae, the molecular connection (tie molecule concentration) between the neighboring PVDF crystals decreases gradually. For the blends with more than 80 wt % PVDF, most of the PVDF α-crystals are transformed into β-crystals upon deformation, and the molecular chains of the β-crystals are aligned along the stretching direction because tie molecules transfer the loading effectively. For the blends with less than 30 wt % PVDF, almost all of the PVDF crystals are isolated from each other with very few tie molecules. Mechanical deformation induces the perpendicular crystal molecular chain arrangement with no crystal form transitions. For the blends with 40 wt % to 70 wt % PVDF, the <i>c</i>-axis-oriented β-phase and the tilt-oriented α-phase coexist in the uniaxially stretched blends. The shape-memory properties of the blends were also evaluated over the same blend composition range. The maximum shape-memory recovery properties were observed for the blend sample containing 50 wt % PVDF, in which a small amount of tie molecules connect the PVDF crystallites to form a deformable elastic network. This network contributes to the good shape-memory properties of the blend. For the blends with very few tie molecules or high tie molecule concentrations, the deformation induces the slipping of the amorphous molecules or the large fibrillar crystal structure, respectively; thus, these samples exhibit relatively low shape-memory performance

Energy stress-induced circZFR enhances oxidative phosphorylation in lung adenocarcinoma via regulating alternative splicing

Abstract Background Circular RNAs (circRNAs) contribute to multiple biological functions and are also involved in pathological conditions such as cancer. However, the role of circRNAs in metabolic reprogramming, especially upon energy stress in lung adenocarcinoma (LUAD), remains largely unknown. Methods Energy stress-induced circRNA was screened by circRNA profiling and glucose deprivation assays. RNA-seq, real-time cell analyzer system (RTCA) and measurement of oxygen consumption rate (OCR) were performed to explore the biological functions of circZFR in LUAD. The underlying mechanisms were investigated using circRNA pull-down, RNA immunoprecipitation, immunoprecipitation and bioinformatics analysis of alternative splicing. Clinical implications of circZFR were assessed in 92 pairs of LUAD tissues and adjacent non-tumor tissues, validated in established patient-derived tumor xenograft (PDTX) model. Results CircZFR is induced by glucose deprivation and is significantly upregulated in LUAD compared to adjacent non-tumor tissues, enhancing oxidative phosphorylation (OXPHOS) for adaptation to energy stress. CircZFR is strongly associated with higher T stage and poor prognosis in patients with LUAD. Mechanistically, circZFR protects heterogeneous nuclear ribonucleoprotein L-like (HNRNPLL) from degradation by ubiquitination to regulate alternative splicing, such as myosin IB (MYO1B), and subsequently activates the AKT-mTOR pathway to facilitate OXPHOS. Conclusion Our study provides new insights into the role of circRNAs in anticancer metabolic therapies and expands our understanding of alternative splicing

Programmable Structure Control in Cigarlike TiO₂ Nanofibers and UV-Light Photocatalysis Performance of Resultant Fabrics

Novel cigarlike nanofibers with an outer-shell and inner-continuous-pore structure and resultant fabrics have been fabricated by coupling the self-assembly of polystyrene-<i>block</i>-poly­(ethylene oxide) (PS-<i>b</i>-PEO) containing titanium precursors with the electrospinning technique in our previous work [You et al. ACS Appl. Mater. Interfaces 2013, 5, 2278]. In the current work, the structure control in these nanofibers has been investigated in detail using scanning electron microscopy, focused ion beam, and small angle X-ray scattering. Our results indicate that electrospinning conditions, the adopted solvent, the volume fraction of PS-<i>b</i>-PEO block copolymer, and the amount of titanium tetraisopropoxide in the mixture produce significant effects on both outer-shell and inner-continuous structures in the nanofibers. The parameters discussed above make it possible to achieve programmable structure control in the aspect of the diameter, thickness of the outer shell, and inner continuous pore. As a result, both micropores among fibers and nanopores in certain fibers are under their control. Furthermore, the photocatalytic activity of resultant TiO₂ fabrics was investigated by taking the photodegradation of Rhodamine B as an example. The results suggest that the degradation efficiency and rate constant exhibit sensitivity on the structure of nanofibers