CCRS proposal for evaluating LANDSAT-D MSS and TM data

Accomplishments in the evaluation of LANDSAT 4 data are reported. The objectives of the Canadian proposal are: (1) to quantify the LANDSAT-4 sensors and system performance for the purpose of updating the radiometric and geometric correction algorithms for MSS and for developing and evaluating new correction algorithms to be used for TM data processing; (2) to compare and access the degree to which LANDSAT-4 MSS data can be integrated with MSS imagery acquired from earlier LANDSAT missions; and (3) to apply image analysis and information extraction techniques for specific user applications such as forestry or agriculture

CCRS proposal for evaluating LANDSAT-4 MSS and TM data

The measurement of registration errors in LANDSAT MSS data is discussed as well as the development of a revised algorithm for the radiometric calibration of TM data and the production of a geocoded TM image

Evaluating LANDSAT-4 MSS and TM data

Interband line pixel misregistrations were determined for the four MSS bands of the Mistassini, Ontario scene and multitemporal registration of LANDSAT-4 products were tested for two different geocoded scenes. Line and pixel misregistrations are tabulated as determined by the manual ground control points and the digital band to band correlation techniques. A method was developed for determining the spectral information content of TM images for forestry applications

Loss of KLP-19 polar ejection force causes misorientation and missegregation of holocentric chromosomes

Holocentric chromosomes assemble kinetochores along their length instead of at a focused spot. The elongated expanse of an individual holocentric kinetochore and its potential flexibility heighten the risk of stable attachment to microtubules from both poles of the mitotic spindle (merotelic attachment), and hence aberrant segregation of chromosomes. Little is known about the mechanisms that holocentric species have evolved to avoid this type of error. Our studies of the influence of KLP-19, an essential microtubule motor, on the behavior of holocentric Caenorhabditis elegans chromosomes suggest that it has a major role in combating merotelic attachments. Depletion of KLP-19, which associates with nonkinetochore chromatin, allows aberrant poleward chromosome motion during prometaphase, misalignment of holocentric kinetochores, and multiple anaphase chromosome bridges in all mitotic divisions. Time-lapse movies of GFP-labeled mono- and bipolar spindles demonstrate that KLP-19 generates a force on relatively stiff holocentric chromosomes that pushes them away from poles. We hypothesize that this polar ejection force minimizes merotelic misattachment by maintaining a constant tension on pole–kinetochore connections throughout prometaphase, tension that compels sister kinetochores to face directly toward opposite poles

Translational energy dependence of cross sections for reactions of OH− (H2O) n with CO2 and SO2

This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/80/10/10.1063/1.446510.A tandem mass spectrometer has been used to measure cross sections for reactions of the solvated negative ions OH−(H2O) n , where 0≤n≤3, with the neutral molecules CO2 and SO2 over the range of reactant translational energy 0.15–25.0 eV (LAB). The reactions observed include solvent switching, collisional dissociation, and charge transfer. The exoergic solvent switching reactions are very rapid, having cross sections which exceed a hundred square Angstroms at low energies. These cross sections decrease approximately as (energy)−0.5 up to 1 eV and then decrease much more rapidly at higher collision energies. Estimates of bond dissociation energies for the cluster ions are derived from the measured translational energy thresholds for the endothermic collisional dissociationreactions

Repression of Germline Genes in \u3cem\u3eCaenorhabditis elegans\u3c/em\u3e Somatic Tissues by H3K9 Dimethylation of Their Promoters

Repression of germline-promoting genes in somatic cells is critical for somatic development and function. To study how germline genes are repressed in somatic tissues, we analyzed key histone modifications in three Caenorhabditis elegans synMuv B mutants, lin-15B, lin-35, and lin-37—all of which display ectopic expression of germline genes in the soma. LIN-35 and LIN-37 are members of the conserved DREAM complex. LIN-15B has been proposed to work with the DREAM complex but has not been shown biochemically to be a member of the complex. We found that, in wild-type worms, synMuv B target genes and germline genes are enriched for the repressive histone modification dimethylation of histone H3 on lysine 9 (H3K9me2) at their promoters. Genes with H3K9me2 promoter localization are evenly distributed across the autosomes, not biased toward autosomal arms, as are the broad H3K9me2 domains. Both synMuv B targets and germline genes display a dramatic reduction of H3K9me2 promoter localization in lin-15B mutants, but much weaker reduction in lin-35 and lin-37mutants. This difference between lin-15B and DREAM complex mutants likely represents a difference in molecular function for these synMuv B proteins. In support of the pivotal role of H3K9me2 in regulation of germline genes by LIN-15B, global loss of H3K9me2 but not H3K9me3 results in phenotypes similar to synMuv B mutants, high-temperature larval arrest, and ectopic expression of germline genes in the soma. We propose that LIN-15B-driven enrichment of H3K9me2 at promoters of germline genes contributes to repression of those genes in somatic tissues

Trans-generational epigenetic regulation of C. elegans primordial germ cells

<p>Abstract</p> <p>Background</p> <p>The processes through which the germline maintains its continuity across generations has long been the focus of biological research. Recent studies have suggested that germline continuity can involve epigenetic regulation, including regulation of histone modifications. However, it is not clear how histone modifications generated in one generation can influence the transcription program and development of germ cells of the next.</p> <p>Results</p> <p>We show that the histone H3K36 methyltransferase maternal effect sterile (MES)-4 is an epigenetic modifier that prevents aberrant transcription activity in <it>Caenorhabditis elegans </it>primordial germ cells (PGCs). In <it>mes-4 </it>mutant PGCs, RNA Pol II activation is abnormally regulated and the PGCs degenerate. Genetic and genomewide analyses of MES-4-mediated H3K36 methylation suggest that MES-4 activity can operate independently of ongoing transcription, and may be predominantly responsible for maintenance methylation of H3K36 in germline-expressed loci.</p> <p>Conclusions</p> <p>Our data suggest a model in which MES-4 helps to maintain an 'epigenetic memory' of transcription that occurred in germ cells of previous generations, and that MES-4 and its epigenetic product are essential for normal germ cell development.</p

The DREAM complex promotes gene body H2A.Z for target repression.

The DREAM (DP, Retinoblastoma [Rb]-like, E2F, and MuvB) complex controls cellular quiescence by repressing cell cycle genes, but its mechanism of action is poorly understood. Here we show that Caenorhabditis elegans DREAM targets have an unusual pattern of high gene body HTZ-1/H2A.Z. In mutants of lin-35, the sole p130/Rb-like gene in C. elegans, DREAM targets have reduced gene body HTZ-1/H2A.Z and increased expression. Consistent with a repressive role for gene body H2A.Z, many DREAM targets are up-regulated in htz-1/H2A.Z mutants. Our results indicate that the DREAM complex facilitates high gene body HTZ-1/H2A.Z, which plays a role in target gene repression.We are grateful to D. Fay for providing the 5× outcrossed lin-35 strain, and Robert Horvitz for antibodies. I.L., M.A.C., P.S., A.A., and J.A. were supported by Wellcome Trust Senior Research Fellowships to J.A. (054523 and 101863). J.A. also acknowledges support by core funding from the Wellcome Trust and Cancer Research UK. J.M.G. and S.S. were supported by National Institutes of Health (NIH) R01 grant GM34059. Part of this work was supported by NIH National Human Genome Research Institute (NHGRI) grant U01 HG004270 to the modENCODE consortium headed by J.D. Lieb.This is the final version of the article. It first appeared from CSH Press via http://dx.doi.org/10.1101/gad.255810.11

The Histone H3K36 Methyltransferase MES-4 Acts Epigenetically to Transmit the Memory of Germline Gene Expression to Progeny

Methylation of histone H3K36 in higher eukaryotes is mediated by multiple methyltransferases. Set2-related H3K36 methyltransferases are targeted to genes by association with RNA Polymerase II and are involved in preventing aberrant transcription initiation within the body of genes. The targeting and roles of the NSD family of mammalian H3K36 methyltransferases, known to be involved in human developmental disorders and oncogenesis, are not known. We used genome-wide chromatin immunoprecipitation (ChIP) to investigate the targeting and roles of the Caenorhabditis elegans NSD homolog MES-4, which is maternally provided to progeny and is required for the survival of nascent germ cells. ChIP analysis in early C. elegans embryos revealed that, consistent with immunostaining results, MES-4 binding sites are concentrated on the autosomes and the leftmost ∼2% (300 kb) of the X chromosome. MES-4 overlies the coding regions of approximately 5,000 genes, with a modest elevation in the 5′ regions of gene bodies. Although MES-4 is generally found over Pol II-bound genes, analysis of gene sets with different temporal-spatial patterns of expression revealed that Pol II association with genes is neither necessary nor sufficient to recruit MES-4. In early embryos, MES-4 associates with genes that were previously expressed in the maternal germ line, an interaction that does not require continued association of Pol II with those loci. Conversely, Pol II association with genes newly expressed in embryos does not lead to recruitment of MES-4 to those genes. These and other findings suggest that MES-4, and perhaps the related mammalian NSD proteins, provide an epigenetic function for H3K36 methylation that is novel and likely to be unrelated to ongoing transcription. We propose that MES-4 transmits the memory of gene expression in the parental germ line to offspring and that this memory role is critical for the PGCs to execute a proper germline program

Multiple determination of the optical constants of thin-film coating materials

The seven participating laboratories received films of two different thicknesses of Sc2O3 and Rh. All samples of each material were prepared in a single deposition run. Brief descriptions are given of the various methods used for determination of the optical constants of these coating materials. The measurement data are presented, and the results are compared. The mean of the variances of the Sc2O3refractive-index determinations in the 0.40–0.75-nm spectral region was 0.03. The corresponding variances for the refractive index and absorption coefficient of Rh were 0.35 and 0.26, respectively