Jagged2a-Notch Signaling Mediates Cell Fate Choice in the Zebrafish Pronephric Duct

Pronephros, a developmental model for adult mammalian kidneys (metanephros) and a functional kidney in early teleosts, consists of glomerulus, tubule, and duct. These structural and functional elements are responsible for different kidney functions, e.g., blood filtration, waste extraction, salt recovery, and water balance. During pronephros organogenesis, cell differentiation is a key step in generating different cell types in specific locations to accomplish designated functions. However, it is poorly understood what molecules regulate the differentiation of different cell types in different parts of the kidney. Two types of epithelial cells, multi-cilia cells and principal cells, are found in the epithelia of the zebrafish distal pronephric duct. While the former is characterized by at least 15 apically localized cilia and expresses centrin2 and rfx2, the latter is characterized by a single primary cilium and sodium pumps. Multi-cilia cells and principal cells differentiate from 17.5 hours post-fertilization onwards in a mosaic pattern. Jagged2a-Notch1a/Notch3-Her9 is responsible for specification and patterning of these two cell types through a lateral inhibition mechanism. Furthermore, multi-cilia cell hyperplasia was observed in mind bomb mutants and Mind bomb was shown to interact with Jagged2a and facilitate its internalization. Taken together, our findings add a new paradigm of Notch signaling in kidney development, namely, that Jagged2a-Notch signaling modulates cell fate choice in a nephric segment, the distal pronephric duct

Fractal Modeling of Pore Structure and Ionic Diffusivity for Cement Paste

Pore structure in cement based composites is of paramount importance to ionic diffusivity. In this paper, pore structure in cement paste is modeled by means of the recently proposed solid mass fractal model. Moreover, an enhanced Maxwell homogenization method that incorporates the solid mass fractal model is proposed to determine the associated ionic diffusivity. Experiments are performed to validate the modeling, that is, mercury intrusion porosimetry and rapid chloride migration. Results indicate that modeling agrees well with those obtained from experiments

INFLUENCE OF ENVIRONMENTAL CONDITIONS ON RELEASE RULES OF FERTILIZER FROM WOOD RESIDUE SLOW-RELEASE FERTILIZER SHELL

Slow/controlled-release fertilizer is a kind of fertilizer that controls or slows down the nutrient release rate according to a specific release rate or release period. The development and application of slow/controlled-release fertilizer is highly valued all over the world because of its benefits. However, the materials used for the fertilizer coating are mostly difficult to degrade, causing many negative effects to the environment. Wood is a porous material that could be used as a coating material through which fertilizers could infiltrate. In addition, a shell glued with adhesives could degrade in soil because of the loose structure, providing another channel for infiltration of fertilizer. As a kind of environmental friendly material, a wood residue fertilizer shell could be used to provide fertilizer for trees, flowers, and other plants. Toona sinensis wood residues were used as the raw material to manufacture a slow-release fertilizer shell using thesecondary molding method. The influence of external environmental conditions such as temperature andrainfall on the release rules of fertilizers from shells were studied through artificial rainfall simulation. Results showed that release rules were similar in three sets of rainfall. The release amount increased quickly at the early stages and then decreased gradually. Also, the release amount changed as rainfall increased. Temperature also had a major influence on release rate of fertilizer from the shell. Generally, the release rate of fertilizer in the shell increased with increase of environmental temperature. The release amount kept relatively stable at lower temperatures. This study indicated that the wood residue shell could slow down the release of fertilizer. Both rainfall and temperature had a great influence on the release rate of fertilizer from the shell

The chemokine Sdf-1 and its receptor Cxcr4 are required for formation of muscle in zebrafish

<p>Abstract</p> <p>Background</p> <p>During development cell migration takes place prior to differentiation of many cell types. The chemokine receptor Cxcr4 and its ligand Sdf1 are implicated in migration of several cell lineages, including appendicular muscles.</p> <p>Results</p> <p>We dissected the role of <it>sdf1</it>-<it>cxcr4 </it>during skeletal myogenesis. We demonstrated that the receptor <it>cxcr4a </it>is expressed in the medial-anterior part of somites, suggesting that chemokine signaling plays a role in this region of the somite. Previous reports emphasized co-operation of Sdf1a and Cxcr4b. We found that during early myogenesis Sdf1a co-operates with the second Cxcr4 of zebrafish – Cxcr4a resulting in the commitment of myoblast to form fast muscle. Disrupting this chemokine signal caused a reduction in <it>myoD </it>and <it>myf5 </it>expression and fast fiber formation. In addition, we showed that a dimerization partner of MyoD and Myf5, E12, positively regulates transcription of <it>cxcr4a </it>and <it>sdf1a </it>in contrast to that of Sonic hedgehog, which inhibited these genes through induction of expression of <it>id2</it>.</p> <p>Conclusion</p> <p>We revealed a regulatory feedback mechanism between <it>cxcr4a</it>-<it>sdf1a </it>and genes encoding myogenic regulatory factors, which is involved in differentiation of fast myofibers. This demonstrated a role of chemokine signaling during development of skeletal muscles.</p

Discovery of gamma-ray emission from a strongly lobe-dominated quasar 3C 275.1

We systematically analyze the 6-year {\it Fermi}/LAT data of the lobe-dominated quasars (LDQs) in the complete LDQ sample from 3CRR survey and report the discovery of high-energy $\gamma$-ray emission from 3C 275.1. The $\gamma$-ray emission of 3C 207 is confirmed and significant variability of the lightcurve is identified. We do not find statistically significant $\gamma$-ray emission from other LDQs. 3C 275.1 is the known $\gamma$-ray quasar with the lowest core dominance parameter (i.e., $R=0.11$). We also show that both the northern radio hotspot and parsec jet models can reasonably reproduce the $\gamma$-ray data. The parsec jet model, however, is favored by the potential $\gamma$-ray variability at the timescale of months. We suggest that some dimmer $\gamma$-ray LDQs will be detected in the future and LDQs could contribute non-negligibly to the extragalactic $\gamma$-ray background.Comment: 26 pages, 10 figures, 3 tables; ApJ in pres

Temporal Notch activation through Notch1a and Notch3 is required for maintaining zebrafish rhombomere boundaries

In vertebrates, hindbrain is subdivided into seven segments termed rhombomeres and the interface between each rhombomere forms the boundary. Similar to the D/V boundary formation in Drosophila, Notch activation has been shown to regulate the segregation of rhombomere boundary cells. Here we further explored the function of Notch signaling in the formation of rhombomere boundaries. By using bodipy ceramide cell-labeling technique, we found that the hindbrain boundary is formed initially in mib mutants but lost after 24 hours post-fertilization (hpf). This phenotype was more severe in mibta52b allele than in mibtfi91 allele. Similarly, injection of su(h)-MO led to boundary defects in a dosage-dependent manner. Boundary cells were recovered in mibta52b mutants in the hdac1-deficient background, where neurogenesis is inhibited. Furthermore, boundary cells lost sensitivity to reduced Notch activation from 15 somite stage onwards. We also showed that knockdown of notch3 function in notch1a mutants leads to the loss of rhombomere boundary cells and causes neuronal hyperplasia, indicating that Notch1a and Notch3 play a redundant role in the maintenance of rhombomere boundary

Genome-wide loss-of-function analysis of deubiquitylating enzymes for zebrafish development

<p>Abstract</p> <p>Background</p> <p>Deconjugation of ubiquitin and/or ubiquitin-like modified protein substrates is essential to modulate protein-protein interactions and, thus, signaling processes in cells. Although deubiquitylating (deubiquitinating) enzymes (DUBs) play a key role in this process, however, their function and regulation remain insufficiently understood. The "loss-of-function" phenotype studies can provide important information to elucidate the gene function, and zebrafish is an excellent model for this goal.</p> <p>Results</p> <p>From an <it>in silico </it>genome-wide search, we found more than 90 putative DUBs encoded in the zebrafish genome belonging to six different subclasses. Out of them, 85 from five classical subclasses have been tested with morpholino (MO) knockdown experiments and 57 of them were found to be important in early development of zebrafish. These DUB morphants resulted in a complex and pleiotropic phenotype that, regardless of gene target, always affected the notochord. Based on the <it>huC </it>neuronal marker expression, we grouped them into five sets (groups I to V). Group I DUBs (<it>otud7b, uchl3 </it>and <it>bap1</it>) appear to be involved in the Notch signaling pathway based on the neuronal hyperplasia, while group IV DUBs (<it>otud4, usp5, usp15 </it>and <it>usp25</it>) play a critical role in dorsoventral patterning through the BMP pathway.</p> <p>Conclusion</p> <p>We have identified an exhaustive list of genes in the zebrafish genome belonging to the five established classes of DUBs. Additionally, we performed the corresponding MO knockdown experiments in zebrafish as well as functional studies for a subset of the predicted DUB genes. The screen results in this work will stimulate functional follow-up studies of potential DUB genes using the zebrafish model system.</p