Realization of a two-dimensional checkerboard lattice in monolayer Cu2_2N

Two-dimensional checkerboard lattice, the simplest line-graph lattice, has been intensively studied as a toy model, while material design and synthesis remain elusive. Here, we report theoretical prediction and experimental realization of the checkerboard lattice in monolayer Cu$_2$N. Experimentally, monolayer Cu$_2$N can be realized in the well-known N/Cu(100) and N/Cu(111) systems that were previously mistakenly believed to be insulators. Combined angle-resolved photoemission spectroscopy measurements, first-principles calculations, and tight-binding analysis show that both systems host checkerboard-derived hole pockets near the Fermi level. In addition, monolayer Cu$_2$N has outstanding stability in air and organic solvents, which is crucial for further device applications.Comment: Nano Letters, in pres

Stable Gene Silencing in Zebrafish with Spatiotemporally Targetable RNA Interference

The ability to regulate gene activity in a spatiotemporally controllable manner is vital for biological discovery that will impact disease diagnosis and treatment. While conditional gene silencing is possible in other genetic model organisms, this technology is largely unavailable in zebrafish, an important vertebrate model organism for functional gene discovery. Here, using short hairpin RNAs (shRNAs) designed in the microRNA-30 backbone, which have been shown to mimic natural microRNA primary transcripts and be more effective than simple shRNAs, we report stable RNA interference-mediated gene silencing in zebrafish employing the yeast Gal4-UAS system. Using this approach, we reveal at single-cell resolution the role of atypical protein kinase Cλ (aPKCλ) in regulating neural progenitor/stem cell division. We also show effective silencing of the one-eyed-pinhead and no-tail/brachyury genes. Furthermore, we demonstrate stable integration and germ-line transmission of the UAS-miR-shRNAs for aPKCλ, the expressivity of which is controllable by the strength and expression of Gal4. This technology shall significantly advance the utility of zebrafish for understanding fundamental vertebrate biology and for the identification and evaluation of important therapeutic targets

Stable Gene Silencing in Zebrafish with Spatiotemporally Targetable RNA Interference

The ability to regulate gene activity in a spatiotemporally controllable manner is vital for biological discovery that will impact disease diagnosis and treatment. While conditional gene silencing is possible in other genetic model organisms, this technology is largely unavailable in zebrafish, an important vertebrate model organism for functional gene discovery. Here, using short hairpin RNAs (shRNAs) designed in the microRNA-30 backbone, which have been shown to mimic natural microRNA primary transcripts and be more effective than simple shRNAs, we report stable RNA interference-mediated gene silencing in zebrafish employing the yeast Gal4-UAS system. Using this approach, we reveal at single-cell resolution the role of atypical protein kinase Cλ (aPKCλ) in regulating neural progenitor/stem cell division. We also show effective silencing of the one-eyed-pinhead and no-tail/brachyury genes. Furthermore, we demonstrate stable integration and germ-line transmission of the UAS-miR-shRNAs for aPKCλ, the expressivity of which is controllable by the strength and expression of Gal4. This technology shall significantly advance the utility of zebrafish for understanding fundamental vertebrate biology and for the identification and evaluation of important therapeutic targets

Distributed Fiberoptic Sensor for Simultaneous Temperature and Strain Monitoring Based on Brillouin Scattering Effect in Polyimide-Coated Fibers

A unique multiparameter sensor for distributed measurement of temperature and strain based on spontaneous Brillouin scattering in polyimide-coated optical fiber is proposed, which is an excellent candidate for the cross-sensitivity problem in conventional Brillouin sensing network. In the experimental section, the discrimination of strain and temperature is successfully demonstrated by analysing the unequal sensing coefficients of the Brillouin frequency shifts generated by different acoustic modes. The Brillouin frequency shifts of the main two peaks are successfully measured to discriminate the strain and temperature with an accuracy 19.68 με and 1.02°C in 2.5 km sensing range. The proposed distributed Brillouin optical fiber sensor allows simultaneous measurement of temperature and strain, thus opening a door for practical application such as oil explorations

Imaging-based chemical screening reveals activity-dependent neural differentiation of pluripotent stem cells.

Mammalian pluripotent stem cells (PSCs) represent an important venue for understanding basic principles regulating tissue-specific differentiation and discovering new tools that may facilitate clinical applications. Mechanisms that direct neural differentiation of PSCs involve growth factor signaling and transcription regulation. However, it is unknown whether and how electrical activity influences this process. Here we report a high throughput imaging-based screen, which uncovers that selamectin, an anti-helminthic therapeutic compound with reported activity on invertebrate glutamate-gated chloride channels, promotes neural differentiation of PSCs. We show that selamectins pro-neurogenic activity is mediated by γ2-containing GABAA receptors in subsets of neural rosette progenitors, accompanied by increased proneural and lineage-specific transcription factor expression and cell cycle exit. In vivo, selamectin promotes neurogenesis in developing zebrafish. Our results establish a chemical screening platform that reveals activity-dependent neural differentiation from PSCs. Compounds identified in this and future screening might prove therapeutically beneficial for treating neurodevelopmental or neurodegenerative disorders. DOI:http://dx.doi.org/10.7554/eLife.00508.001

Heterogeneously expressed fezf2 patterns gradient Notch activity in balancing the quiescence, proliferation, and differentiation of adult neural stem cells.

Balancing quiescence, self-renewal, and differentiation in adult stem cells is critical for tissue homeostasis. The underlying mechanisms, however, remain incompletely understood. Here we identify Fezf2 as a novel regulator of fate balance in adult zebrafish dorsal telencephalic neural stem cells (NSCs). Transgenic reporters show intermingled fezf2-GFP(hi) quiescent and fezf2-GFP(lo) proliferative NSCs. Constitutive or conditional impairment of fezf2 activity demonstrates its requirement for maintaining quiescence. Analyses of genetic chimeras reveal a dose-dependent role of fezf2 in NSC activation, suggesting that the difference in fezf2 levels directionally biases fate. Single NSC profiling coupled with genetic analysis further uncovers a fezf2-dependent gradient Notch activity that is high in quiescent and low in proliferative NSCs. Finally, fezf2-GFP(hi) quiescent and fezf2-GFP(lo) proliferative NSCs are observed in postnatal mouse hippocampus, suggesting possible evolutionary conservation. Our results support a model in which fezf2 heterogeneity patterns gradient Notch activity among neighbors that is critical to balance NSC fate

Heterogeneously Expressed fezf2 Patterns Gradient Notch Activity in Balancing the Quiescence, Proliferation, and Differentiation of Adult Neural Stem Cells

Balancing quiescence, self-renewal, and differentiation in adult stem cells is critical for tissue homeostasis. The underlying mechanisms, however, remain incompletely understood. Here we identify Fezf2 as a novel regulator of fate balance in adult zebrafish dorsal telencephalic neural stem cells (NSCs). Transgenic reporters show intermingled fezf2-GFP(hi) quiescent and fezf2-GFP(lo) proliferative NSCs. Constitutive or conditional impairment of fezf2 activity demonstrates its requirement for maintaining quiescence. Analyses of genetic chimeras reveal a dose-dependent role of fezf2 in NSC activation, suggesting that the difference in fezf2 levels directionally biases fate. Single NSC profiling coupled with genetic analysis further uncovers a fezf2-dependent gradient Notch activity that is high in quiescent and low in proliferative NSCs. Finally, fezf2-GFP(hi) quiescent and fezf2-GFP(lo) proliferative NSCs are observed in postnatal mouse hippocampus, suggesting possible evolutionary conservation. Our results support a model in which fezf2 heterogeneity patterns gradient Notch activity among neighbors that is critical to balance NSC fate