Zinc transporters ZIPT-2.4 and ZIPT-15 are required for normal C. elegans fecundity.

PURPOSE: The requirement of zinc for the development and maturation of germ lines and reproductive systems is deeply conserved across evolution. The nematode Caenorhabditis elegans offers a tractable platform to study the complex system of distributing zinc to the germ line. We investigated several zinc importers to investigate how zinc transporters play a role in the reproductive system in nematodes, as well as establish a platform to study zinc transporter biology in germline and reproductive development. METHODS: Previous high throughput transcriptional datasets as well as phylogenetic analysis identified several putative zinc transporters that have a function in reproduction in worms. Phenotypic analysis of CRISPR-generated knockouts and tags included characterization of offspring output, gonad development, and protein localization. Light and immunofluorescence microscopy allowed for visualization of physiological and molecular effects of zinc transporter mutations. RESULTS: Disruption of two zinc transporters, ZIPT-2.4 and ZIPT-15, was shown to lead to defects in reproductive output. A mutation in zipt-2.4 has subtle effects on reproduction, while a mutation in zipt-15 has a clear impact on gonad and germline development that translates into a more pronounced defect in fecundity. Both transporters have germline expression, as well as additional expression in other cell types. CONCLUSIONS: Two ZIP-family zinc transporter orthologs of human ZIP6/10 and ZIP1/2/3 proteins are important for full reproductive fecundity and participate in development of the gonad. Notably, these zinc transporters are present in gut and reproductive tissues in addition to the germ line, consistent with a complex zinc trafficking network important for reproductive success.

Dynamic zinc fluxes regulate meiotic progression in Caenorhabditis elegans†.

Zinc influx and efflux events are essential for meiotic progression in oocytes of several mammalian and amphibian species, but it is less clear whether this evolutionary conservation of zinc signals is also important in late-stage germline development in invertebrates. Using quantitative, single cell elemental mapping methods, we find that Caenorhabditis elegans oocytes undergo significant stage-dependent fluctuations in total zinc content, rising by over sevenfold from Prophase I through the beginning of mitotic divisions in the embryo. Live imaging of the rapid cell cycle progression in C. elegans enables us to follow changes in labile zinc pools across meiosis and mitosis in single embryo. We find a dynamic increase in labile zinc prior to fertilization that then decreases from Anaphase II through pronuclear fusion and relocalizes to the eggshell. Disruption of these zinc fluxes blocks extrusion of the second polar body, leading to a range of mitotic defects. We conclude that spatial temporal zinc fluxes are necessary for meiotic progression in C. elegans and are a conserved feature of germ cell development in a broad cross section of metazoa.

Interrogating Intracellular Zinc Chemistry with a Long Stokes Shift Zinc Probe ZincBY-4.

Previous work has shown that fluctuations in zinc content and subcellular localization play key roles in regulating cell cycle progression; however, a deep mechanistic understanding requires the determination of when, where, and how labile zinc pools are concentrated into or released from stores. Labile zinc ions can be difficult to detect with probes that require hydrolysis of toxic protecting groups or application at high concentrations that negatively impact cell function. We previously reported a BODIPY-based zinc probe, ZincBY-1, that can be used at working concentrations that are 20-200-fold lower than concentrations employed with other probes. To better understand how zinc pools can be visualized at such low probe concentrations, we modulated the photophysical properties via changes at the 5-position of the BODIPY core. One of these, ZincBY-4, exhibits an order of magnitude higher affinity for zinc, an 8-fold increase in brightness in response to zinc, and a 100 nm Stokes shift within cells. The larger Stokes shift of ZincBY-4 presents a unique opportunity for simultaneous imaging with GFP or fluorescein sensors upon single excitation. Finally, by creating a proxy for the cellular environment in spectrometer experiments, we show that the ZincBY series are highly effective at 50 nM because they can pass membranes and accumulate in regions of high zinc concentration within a cell. These features of the ZincBY probe class have widespread applications in imaging and for understanding the regulatory roles of zinc fluxes in live cells.

Shaping the synthesis and assembly of symmetrically stellated Au/Pd nanocrystals with aromatic additives.

Au/Pd octopods were synthesized with enhanced sample homogeneity through the use of aromatic additives. This increase in sample monodispersity facilitates large-area periodic assembly of stellated metal nanostructures for the first time. The aromatic additives were also found to influence the structures of the stellated nanocrystals with subtle shape modifications observed that can alter the packing arrangement of the Au/Pd octopods. These results indicate the possibility of tailored assembly of stellated nanostructures, which would be useful for optical applications that require strong and predictable coupling between plasmonic building blocks.

Seed-mediated co-reduction: a versatile route to architecturally controlled bimetallic nanostructures.

Gold-palladium octopods and new concave and shape-controlled alloy nanostructures are synthesized by seed-mediated co-reduction, wherein two metal precursors are reduced in the presence of seeds that serve as preferential sites for the growth of the larger nanostructures. Here, the first comprehensive study of this technique is presented in a model Au-Pd system and provides insight into the mechanism of formation for these architecturally distinct nanocrystals. A systematic evaluation of synthesis conditions decoupled the roles of (i) Au:Pd precursor ratio, (ii) reaction pH, and (iii) capping agent concentration in morphology development. These factors provide control of growth kinetics and ultimately the morphology and composition of the final nanostructures. Significantly, elucidating the overgrowth processes during seed-mediated co-reduction will lead to the synthesis of other architecturally controlled bimetallic nanocrystals.