Graphene nanoplatelets (GNPs) were used as reinforcement in AgCuTi filler for brazing SiC ceramic. Ti from the filler reacted with SiC ceramic to form TiC and Ti5Si3 adjacent to the SiC ceramic. ...According to the TEM and HRTEM results, TiC layer exhibited good lattice matching with SiC substrate. TiC particles synthesized by the reaction between Ti and GNPs in situ promoted the heterogeneous nucleation of TiCu and Cu(s,s), and contributed to the refinement of microstructure. Shear tests results indicated that the adoption of GNPs affected the joint property significantly. The TiC particles and an appropriate TiC + Ti5Si3 layer thickness both relieved the residual stress of the brazed joint and thereby increased the joint strength. The shear strength of the joint reached the maximum value of 38 MPa when using AgCuTi/GNPs (GNPs reinforced AgCuTi) composite filler containing 1% GNPs, which was ∼139% higher than that of the joint brazed with AgCuTi filler.
Germ granules, condensates of phase-separated RNA and protein, are organelles that are essential for germline development in different organisms. The patterning of the granules and their relevance ...for germ cell fate are not fully understood. Combining three-dimensional in vivo structural and functional analyses, we study the dynamic spatial organization of molecules within zebrafish germ granules. We find that the localization of RNA molecules to the periphery of the granules, where ribosomes are localized, depends on translational activity at this location. In addition, we find that the vertebrate-specific Dead end (Dnd1) protein is essential for nanos3 RNA localization at the condensates’ periphery. Accordingly, in the absence of Dnd1, or when translation is inhibited, nanos3 RNA translocates into the granule interior, away from the ribosomes, a process that is correlated with the loss of germ cell fate. These findings highlight the relevance of sub-granule compartmentalization for post-transcriptional control and its importance for preserving germ cell totipotency.
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•The border of phase-separated germ granules is enriched with ribosomes•The presence of mRNAs at the granule periphery depends on their translational activity•Localization of nanos3 mRNA to the granule border requires Dnd1 function•Inhibition of nanos3 RNA translation leads to the loss of germ cell fate
Westerich et al. study the distribution of RNA molecules within phase-separated organelles. They find that the presence of mRNAs at the periphery of germ cell granules requires RNA translation and interaction with specific RNA-binding proteins, and they show that mislocalization of RNAs is correlated with loss of germ cell fate.
Robust methods are critical for testing the in vivo regulatory mechanism of RNA binding proteins. Here we report improvement of a protein-mRNA tethering assay to probe the function of an RNA binding ...protein in its natural context within the
adult germline. The assay relies on a dual reporter expressing two mRNAs from a single promoter and resolved by trans-splicing. The
reporter 3'UTR harbors functional binding elements for λN22 peptide, while the
reporter 3'UTR carries mutated nonfunctional elements. This strategy enables internally controlled quantitation of reporter protein by immunofluorescence and mRNA by smFISH. To test the new system, we analyzed a
Nanos protein, NOS-3, which serves as a post-transcriptional regulator of germ cell fate. Unexpectedly, tethered NOS-3 enhanced reporter expression. We confirmed this enhancement activity with a second reporter engineered at an endogenous germline gene. NOS-3 enhancement of reporter expression was associated with its amino-terminal intrinsically disordered region, not its carboxy-terminal zinc fingers. RNA quantitation revealed that tethered NOS-3 enhances stability of the reporter mRNA. We suggest that this direct NOS-3 enhancement activity may explain a paradox: Classically Nanos proteins are expected to repress RNA, but
had been found to promote
expression, an effect that could be direct. Regardless, the new dual reporter dramatically improves in situ quantitation of reporter expression after RNA binding protein tethering to determine its molecular mechanism in a multicellular tissue.
Communication in bilaterian nervous systems is mediated by electrical and secreted signals; however, the evolutionary origin and relation of neurons to other secretory cell types has not been ...elucidated. Here, we use developmental single-cell RNA sequencing in the cnidarian Nematostella vectensis, representing an early evolutionary lineage with a simple nervous system. Validated by transgenics, we demonstrate that neurons, stinging cells, and gland cells arise from a common multipotent progenitor population. We identify the conserved transcription factor gene SoxC as a key upstream regulator of all neuroglandular lineages and demonstrate that SoxC knockdown eliminates both neuronal and secretory cell types. While in vertebrates and many other bilaterians neurogenesis is largely restricted to early developmental stages, we show that in the sea anemone, differentiation of neuroglandular cells is maintained throughout all life stages, and follows the same molecular trajectories from embryo to adulthood, ensuring lifelong homeostasis of neuroglandular cell lineages.
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•Development and homeostasis of a sea anemone is captured at single-cell resolution•Developmental differentiation trajectories are maintained throughout the life cycle•Neurons, gland, and stinging cells derive from a common pool of putative stem cells•SoxC is an upstream regulator of neural progenitor cell specification
Steger et al. present a temporal and spatially resolved single-cell RNA-seq atlas of a sea anemone that recapitulates development and homeostasis. Differentiation trajectories are shown to be maintained throughout the life cycle of Nematostella vectensis, in which SoxC specifies a neuroglandular progenitor population that differentiates into neurons, gland cells, and cnidocytes.
Artemia is not only a crucial live food source in fish and crustacean larviculture but also an ideal experimental organism for biological studies. Female Artemia subjects release either ...diapause-encysted embryos (cysts) via oviparous reproduction or nauplii via ovoviviparous reproduction. As a maternal effector gene, nanos is involved in the differentiation and migration of primordial germ cells. In the present study, the open reading frame (ORF) of the nanos gene of Artemia parthenogenetica was screened and analyzed. Nanos cDNA contained a 933-bp ORF, encoding 310 amino acids with a conserved zinc-finger motif. The expression patterns of nanos in various tissues and during embryo development in Artemia were analyzed by qRT-PCR. The results showed that nanos was specifically expressed in the ovary, with the highest expression being observed during early ovary development. Moreover, nanos knockdown induced by dsRNA injection significantly decreased the gene and protein expression levels of nanos. In addition, knockdown of nanos resulted in an obvious shift from ovoviviparity to oviparity and a reduced number of offspring, corresponding to irregular oocyte shape, cell membrane damage, and cytoplasmic vacuolization. Our study suggests that nanos not only regulates the ovary development and reproductive performance of Artemia but also play a critical role in determining its reproductive mode. This study will improve our knowledge of the role of nanos in the reproductive process of Artemia and the molecular mechanisms underlying reproduction in this shrimp.
•The nanos gene was specifically expressed in the ovary of Artemia.•The nanos gene can regulate the reproductive fecundity and interfere the reproduction mode of Artemia.•This study improve the artificial breeding and the sustainable development of the Artemia and aquaculture industry.
Ferromagnetic films down to thicknesses of tens of nanometers and composed by polycrystalline Fe and Fe
O
nanopillars are grown in large areas by glancing angle deposition with magnetron sputtering ...(MS-GLAD). The morphological features of these films strongly depend on the growth conditions. Vertical or tilted nanopillars have been fabricated depending on whether the substrate is kept rotating azimuthally during deposition or not, respectively. The magnetic properties of these nanopillars films, such as hysteresis loops squareness, adjustable switching fields, magnetic anisotropy and coercivity, can be tuned with the specific morphology. In particular, the growth performed through a collimator mask mounted onto a not rotating azimuthally substrate produces almost isolated well-defined tilted nanopillars that exhibit a magnetic hardening. The first-order reversal curves diagrams and micromagnetic simulations revealed that a growth-induced uniaxial anisotropy, associated with an anisotropic surface morphology produced by the glancing angle deposition in the direction perpendicular to the atomic flux, plays an important role in the observed magnetic signatures. These results demonstrate the potential of the MS-GLAD method to fabricate nanostructured films in large area with tailored structural and magnetic properties for technological applications.
Maintaining cell fate relies on robust mechanisms that prevent the differentiation of specified cells into other cell types. This is especially critical during embryogenesis, when extensive cell ...proliferation, patterning, and migration events take place. Here we show that vertebrate primordial germ cells (PGCs) are protected from reprogramming into other cell types by the RNA-binding protein Dead end (Dnd). PGCs knocked down for Dnd lose their characteristic morphology and adopt various somatic cell fates. Concomitantly, they gain a gene expression profile reflecting differentiation into cells of different germ layers, in a process that we could direct by expression of specific cell-fate determinants. Importantly, we visualized these events within live zebrafish embryos, which provide temporal information regarding cell reprogramming. Our results shed light on the mechanisms controlling germ cell fate maintenance and are relevant for the formation of teratoma, a tumor class composed of cells from more than one germ layer.
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•During their migration through the embryo, PGCs maintain their germline fate•Dnd-deficient zebrafish PGCs transdifferentiate into somatic cells•Dnd-deficient PGCs gain somatic gene expression profile and morphology•Germline-to-soma transdifferentiation can be visualized in vivo
Primordial germ cells (PGCs) maintain their fate during their migration within the embryo. Through monitoring PGCs in live zebrafish embryos, Gross-Thebing et al. uncover a key role for the vertebrate-specific RNA-binding protein Dead end (Dnd) in protecting and maintaining germ cell fate. Dnd-deficient germ cells transdifferentiate into somatic cells.
Nanos gene plays an important role in germline development in animals. However, the molecular mechanisms involved in germline development in Mollusca, the second largest animal phylum, are still ...poorly understood. Here we identified the Nanos orthologue from the Pacific oyster Crassostrea gigas (Cg-Nanos-like), and investigated the expression patterns of Nanos during gametogenesis and embryogenesis in C. gigas. Tissue expression analysis showed that Cg-Nanos-like was specifically expressed in female gonads. During the reproductive cycle, the expression of Cg-Nanos-like mRNA increased matching the seasonal development of the ovarian tissues in diploids, while the expression levels were significantly lower in the ovaries of sterile triploids compared to diploids. High expression of Cg-Nanos-like transcripts were detected in early embryonic stages, while the expression significantly dropped at gastrulation and was barely detectable in veliger stages. In situ hybridization showed that Cg-Nanos-like was expressed at different stages of developing oocytes, whereas positive signals were detected only in spermatogonia during the spermatogenic cycle. These findings indicated that Cg-Nanos-like was involved in the development of germ cells, and maintenance of oocyte maturation. In early embryogenesis, the transcripts were broadly expressed; following gastrulation, the expression was restricted to two cell clumps, which might be the putative primordial germ cells (PGCs) or their precursors. Based on the results, the formation of the PGCs in C. gigas was consistent with the model of transition from epigenesis to preformation.
•A full-length cDNA (1257 bp) of Nanos from Crassostrea gigas was identified and characterized.•Cg-Nanos-like may play an important role in oocyte maturation in adult oysters.•C. gigas may developed their germline from the subpopulation of mesodermal cells.
Germ granules in Drosophila Trcek, Tatjana; Lehmann, Ruth
Traffic (Copenhagen, Denmark),
September 2019, Volume:
20, Issue:
9
Journal Article
Peer reviewed
Open access
Germ granules are hallmarks of all germ cells. Early ultrastructural studies in Drosophila first described these membraneless granules in the oocyte and early embryo as filled with amorphous to ...fibrillar material mixed with RNA. Genetic studies identified key protein components and specific mRNAs that regulate germ cell‐specific functions. More recently these ultrastructural studies have been complemented by biophysical analysis describing germ granules as phase‐transitioned condensates. In this review, we provide an overview that connects the composition of germ granules with their function in controlling germ cell specification, formation and migration, and illuminate these mysterious condensates as the gatekeepers of the next generation.
Germ granules are a hallmark of all species. In Drosophila, they form by scaffold proteins during oogenesis and persist into embryogenesis. They recruit effector mRNAs and piRNAs, which instruct the germ cell fate. mRNAs specifically translated in germ granules control the formation, number, survival and migration of PGCs and regulate their gene expression. piRNAs help recruit mRNAs and once specified, protect the germline genome from transposon‐induced DNA damage. Drosophila germ granules are therefore biologically active droplets that provide continuity of the species.
RNA granules are membraneless condensates that provide functional compartmentalization within cells. The mechanisms by which RNA granules form are under intense investigation. Here, we characterize ...the role of mRNAs and proteins in the formation of germ granules in Drosophila. Super-resolution microscopy reveals that the number, size, and distribution of germ granules is precisely controlled. Surprisingly, germ granule mRNAs are not required for the nucleation or the persistence of germ granules but instead control their size and composition. Using an RNAi screen, we determine that RNA regulators, helicases, and mitochondrial proteins regulate germ granule number and size, while the proteins of the endoplasmic reticulum, nuclear pore complex, and cytoskeleton control their distribution. Therefore, the protein-driven formation of Drosophila germ granules is mechanistically distinct from the RNA-dependent condensation observed for other RNA granules such as stress granules and P-bodies.
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•The number, size, and distribution of germ granules is precisely regulated•Oskar germ granules do not require RNA for their nucleation and stability•RNA regulators and mitochondrial proteins control germ granule number and size•ER, nuclear pore, and cytoskeletal proteins regulate germ granule distribution
Curnutte et al. observe that germ granule proteins rather than mRNAs promote the nucleation and stability of Oskar germ granules in Drosophila. While RNA regulators and mitochondrial proteins control the number and size of germ granules, the proteins of the ER, nuclear pores, and cytoskeleton control their distribution.
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