Defective Nodal and Cerl2 expression in the Arl13b(hnn) mutant node underlie its heterotaxia

Specification of the left-right axis during embryonic development is critical for the morphogenesis of asymmetric organs such as the heart, lungs, and stomach. The first known left-right asymmetry to occur in the mouse embryo is a leftward fluid flow in the node that is created by rotating cilia on the node surface. This flow is followed by asymmetric expression of Nodal and its inhibitor Cerl2 in the node. Defects in cilia and/or fluid flow in the node lead to defective Nodal and Cerl2 expression and therefore incorrect visceral organ situs. Here we show the cilia protein Arl13b is required for left right axis specification as its absence results in heterotaxia. We find the defect originates in the node where Cerl2 is not downregulated and asymmetric expression of Nodal is not maintained resulting in symmetric expression of both genes. Subsequently, Nodal expression is delayed in the lateral plate mesoderm (LPM). Symmetric Nodal and Cerl2 in the node could result from defects in either the generation and/ or the detection of Nodal flow, which would account for the subsequent defects in the LPM and organ positioning.     

Gene flow patterns of the euphausiid, Meganyctiphanes norvegica, in the NW Atlantic based on mtDNA sequences for cytochrome b and cytochrome oxidase I

Population genetic structure and patterns of gene flow are describedfor the euphausiid, Meganyctiphanes norvegica, in the NW AtlanticOcean based on DNA sequence variation of two regions of mitochondrialDNA (mtDNA). DNA sequences were determined for portions of cytochromeoxidase I (COI; 400 base pairs; 76 individuals) and cytochromeb (CYB; 300 base pairs; 101 individuals) for euphausiids collectedfrom the Gulf of Maine in 1991, the Gulf of St Lawrence in 1993and 1994, the Scotian Shelf in 1994, and Georges Bank in 1994.For comparison, M.norvegica collected from the fjords of westernNorway in 1992 were sequenced for COI (20 individuals) and CYB(18 individuals). COI was less variable than CYB, based on bothhaplotype (h=0.6847 for COI; 0.9077 for CYB) and nucleotidediversities (     

Hemocompatible poly(NIPAm-MBA-AMPS) colloidal nanoparticles as carriers of anti-inflammatory cell penetrating peptides

Anionic copolymer systems containing sulfated monomers have great potential for delivery of cationic therapeutics, but N-isopropylacrylamide (NIPAm) 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) copolymer nanoparticles have seen limited characterization to date with regard to physical properties relevant to loading and release of therapeutics. Characterization of polymeric nanoparticles incorporating AMPS showed an increased size and decreased thermodynamic swelling ratios of AMPS containing particles as compared to NIPAm nanoparticles lacking AMPS. Particles with increasing AMPS addition showed an increased propensity for uniformity, intraparticle colloidal stability, and drug loading capacity. Peptide encapsulated in particles was shielded from peptide degradation in serum. Particles were shown not impede blood coagulation or to cause hemolysis. This study has demonstrated that AMPS incorporation into traditional NIPAm nanoparticles presents a tunable parameter for changing particle LCST, size, swelling ratio, ζ potential, and cationic peptide loading potential. This one-pot synthesis results in a thermosensitive anionic nanoparticle system that is a potentially useful platform to deliver cationic cell penetrating peptides.     

Exploring movement patterns and changing distributions of baleen whales in the western North Atlantic using a decade of passive acoustic data

Six baleen whale species are found in the temperate western North Atlantic Ocean, with limited information existing on the distribution and movement patterns for most. There is mounting evidence of distributional shifts in many species, including marine mammals, likely because of climate‐driven changes in ocean temperature and circulation. Previous acoustic studies examined the occurrence of minke (Balaenoptera acutorostrata) and North Atlantic right whales (NARW; Eubalaena glacialis). This study assesses the acoustic presence of humpback (Megaptera novaeangliae), sei (B. borealis), fin (B. physalus), and blue whales (B. musculus) over a decade, based on daily detections of their vocalizations. Data collected from 2004 to 2014 on 281 bottom‐mounted recorders, totaling 35,033 days, were processed using automated detection software and screened for each species' presence. A published study on NARW acoustics revealed significant changes in occurrence patterns between the periods of 2004–2010 and 2011–2014; therefore, these same time periods were examined here. All four species were present from the Southeast United States to Greenland; humpback whales were also present in the Caribbean. All species occurred throughout all regions in the winter, suggesting that baleen whales are widely distributed during these months. Each of the species showed significant changes in acoustic occurrence after 2010. Similar to NARWs, sei whales had higher acoustic occurrence in mid‐Atlantic regions after 2010. Fin, blue, and sei whales were more frequently detected in the northern latitudes of the study area after 2010. Despite this general northward shift, all four species were detected less on the Scotian Shelf area after 2010, matching documented shifts in prey availability in this region. A decade of acoustic observations have shown important distributional changes over the range of baleen whales, mirroring known climatic shifts and identifying new habitats that will require further protection from anthropogenic threats like fixed fishing gear, shipping, and noise pollution.     

A molecular epidemiological study of var gene diversity to characterize the reservoir of Plasmodium falciparum in humans in Africa

Background

The reservoir of Plasmodium infection in humans has traditionally been defined by blood slide positivity. This study was designed to characterize the local reservoir of infection in relation to the diverse var genes that encode the major surface antigen of Plasmodium falciparum blood stages and underlie the parasite''s ability to establish chronic infection and transmit from human to mosquito.

Methodology/Principal Findings

We investigated the molecular epidemiology of the var multigene family at local sites in Gabon, Senegal and Kenya which differ in parasite prevalence and transmission intensity. 1839 distinct var gene types were defined by sequencing DBLα domains in the three sites. Only 76 (4.1%) var types were found in more than one population indicating spatial heterogeneity in var types across the African continent. The majority of var types appeared only once in the population sample. Non-parametric statistical estimators predict in each population at minimum five to seven thousand distinct var types. Similar diversity of var types was seen in sites with different parasite prevalences.

Conclusions/Significance

Var population genomics provides new insights into the epidemiology of P. falciparum in Africa where malaria has never been conquered. In particular, we have described the extensive reservoir of infection in local African sites and discovered a unique var population structure that can facilitate superinfection through minimal overlap in var repertoires among parasite genomes. Our findings show that var typing as a molecular surveillance system defines the extent of genetic complexity in the reservoir of infection to complement measures of malaria prevalence. The observed small scale spatial diversity of var genes suggests that var genetics could greatly inform current malaria mapping approaches and predict complex malaria population dynamics due to the import of var types to areas where no widespread pre-existing immunity in the population exists.     

Experimental warming alters the community composition,diversity, and N2 fixation activity of peat moss (Sphagnum fallax) microbiomes

Sphagnum‐dominated peatlands comprise a globally important pool of soil carbon (C) and are vulnerable to climate change. While peat mosses of the genus Sphagnum are known to harbor diverse microbial communities that mediate C and nitrogen (N) cycling in peatlands, the effects of climate change on Sphagnum microbiome composition and functioning are largely unknown. We investigated the impacts of experimental whole‐ecosystem warming on the Sphagnum moss microbiome, focusing on N₂ fixing microorganisms (diazotrophs). To characterize the microbiome response to warming, we performed next‐generation sequencing of small subunit (SSU) rRNA and nitrogenase (nifH) gene amplicons and quantified rates of N₂ fixation activity in Sphagnum fallax individuals sampled from experimental enclosures over 2 years in a northern Minnesota, USA bog. The taxonomic diversity of overall microbial communities and diazotroph communities, as well as N₂ fixation rates, decreased with warming (p < 0.05). Following warming, diazotrophs shifted from a mixed community of Nostocales (Cyanobacteria) and Rhizobiales (Alphaproteobacteria) to predominance of Nostocales. Microbiome community composition differed between years, with some diazotroph populations persisting while others declined in relative abundance in warmed plots in the second year. Our results demonstrate that warming substantially alters the community composition, diversity, and N₂ fixation activity of peat moss microbiomes, which may ultimately impact host fitness, ecosystem productivity, and C storage potential in peatlands.     

Rapid discrimination of MHC class I and killer cell lectin-like receptor allele variants by high-resolution melt analysis

Ly49G and H-2 class I D(k) molecules are critical to natural killer cell-mediated viral control. To examine their contributions in greater depth, we established NK gene complex (NKC)/Ly49 congenic strains and a novel genetic model defined by MHC class I D(k) disparity in congenic and transgenic mouse strains. Generation and maintenance of Ly49 and H-2 class I select strains require efficient and reproducible genotyping assays for highly polygenic and polymorphic sequences. Thus, we coupled gene- and allele-specific PCR with high-resolution melt (HRM) analysis to discriminate Ly49g and H-2 class I D and K alleles in select strains and in the F(2) and backcross hybrid offspring of different genetic crosses. We show that HRM typing for these critical immune response genes is fast, accurate, and dependable. We further demonstrate that H-2 class I D HRM typing is competent to detect and quantify transgene copy numbers in different mice with distinct genetic backgrounds. Our findings substantiate the utility and practicality of HRM genotyping for highly related genes and alleles, even those belonging to clustered multigene families. Based on these findings, we envision that HRM is capable to interrogate and quantify gene- and allele-specific variations due to differential regulation of gene expression.     

Phospholipids of the differentiating species of Tetrahymena

The whole-cell phospholipid composition of the six known polymorphic species of Tetrahymena has been examined by [(3)H]acetate and [(3)H]myristic acid radiolabeling, and by gas-liquid chromatography of total phospholipid-bound fatty acids. Five of the polymorphic species contained similar phospholipid profiles following radiolabeling in that phosphatidylethanolamine (PE) was the predominant phospholipid; however, in cells of Tetrahymena patula LFF, aminoethylphosphonolipid was present in amounts nearly equal to PE. Tetrahymena patula LFF contained an unusually large percentage of sphingolipid (16.2% by [(3)H]acetate radiolabeling). Substantial differences were found in the fatty acid profiles of the polymorphic species, which included the degree of fatty acid unsaturation and relative weight percentages of odd-chain fatty acids. Tetrahymena vorax contained a low ratio of unsaturated C(18) fatty acids to saturated C(18) fatty acids as compared with all other species examined. The differentiating species generally contained a lesser percentage of monoenoic fatty acids and a lower ratio of unsaturated C(16) fatty acids to saturated C(16) fatty acids as compared with the two monomorphic species examined.     

The Arabidopsis F-box protein SLEEPY1 targets gibberellin signaling repressors for gibberellin-induced degradation

The nuclear DELLA proteins are highly conserved repressors of hormone gibberellin (GA) signaling in plants. In Arabidopsis thaliana, GA derepresses its signaling pathway by inducing proteolysis of the DELLA protein REPRESSOR OF ga1-3 (RGA). SLEEPY1 (SLY1) encodes an F-box-containing protein, and the loss-of-function sly1 mutant has a GA-insensitive dwarf phenotype and accumulates a high level of RGA. These findings suggested that SLY1 recruits RGA to the SCFSLY1 E3 ligase complex for ubiquitination and subsequent degradation by the 26S proteasome. In this report, we provide new insight into the molecular mechanism of how SLY1 interacts with the DELLA proteins for controlling GA response. By yeast two-hybrid and in vitro pull-down assays, we demonstrated that SLY1 interacts directly with RGA and GA INSENSITIVE (GAI, a closely related DELLA protein) via their C-terminal GRAS domain. The rga and gai null mutations additively suppressed the recessive sly1 mutant phenotype, further supporting the model that SCFSLY1 targets both RGA and GAI for degradation. The N-terminal DELLA domain of RGA previously was shown to be essential for GA-induced degradation. However, we found that this DELLA domain is not required for protein-protein interaction with SLY1 in yeast (Saccharomyces cerevisiae), suggesting that its role is in a GA-triggered conformational change of the DELLA proteins. We also identified a novel gain-of-function sly1-d mutation that increased GA signaling by reducing the levels of the DELLA protein in plants. This effect of sly1-d appears to be caused by an enhanced interaction between sly1-d and the DELLA proteins.