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Molecular and Cellular Biology (1)
PLoS ONE (1)
Ikeda, Takayoshi (3)
Davies, Andrew (1)
Hawks, Christina (1)
Higami, Yoshikazu (1)
Ikeno, Yuji (1)
Jackson, James G. (1)
Kawahara, Toshio (1)
Kirtane, Bhakti (1)
Matzuk, Martin M. (1)
Okimoto, Tomoaki (1)
Pereira-Smith, Olivia M. (1)
Senay, Senait D. (1)
Shimokawa, Isao (1)
Smith, James R. (1)
Tominaga, Kaoru (1)
Tomita, Masato (1)
Worner, Susan P. (1)
Year of Publication
Novel Three-Step Pseudo-Absence Selection Technique for Improved Species Distribution Modelling
Senay, Senait D.
Worner, Susan P.
Pseudo-absence selection for spatial distribution models (SDMs) is the subject of ongoing investigation. Numerous techniques continue to be developed, and reports of their effectiveness vary. Because the quality of presence and absence data is key for acceptable accuracy of correlative SDM predictions, determining an appropriate method to characterise pseudo-absences for SDM’s is vital. The main methods that are currently used to generate pseudo-absence points are: 1) randomly generated pseudo-absence locations from background data; 2) pseudo-absence locations generated within a delimited geographical distance from recorded presence points; and 3) pseudo-absence locations selected in areas that are environmentally dissimilar from presence points. There is a need for a method that considers both geographical extent and environmental requirements to produce pseudo-absence points that are spatially and ecologically balanced. We use a novel three-step approach that satisfies both spatial and ecological reasons why the target species is likely to find a particular geo-location unsuitable. Step 1 comprises establishing a geographical extent around species presence points from which pseudo-absence points are selected based on analyses of environmental variable importance at different distances. This step gives an ecologically meaningful explanation to the spatial range of background data, as opposed to using an arbitrary radius. Step 2 determines locations that are environmentally dissimilar to the presence points within the distance specified in step one. Step 3 performs K-means clustering to reduce the number of potential pseudo-absences to the desired set by taking the centroids of clusters in the most environmentally dissimilar class identified in step 2. By considering spatial, ecological and environmental aspects, the three-step method identifies appropriate pseudo-absence points for correlative SDMs. We illustrate this method by predicting the New Zealand potential distribution of the Asian tiger mosquito (Aedes albopictus) and the Western corn rootworm (Diabrotica virgifera virgifera).
MRG15 Regulates Embryonic Development and Cell Proliferation
Jackson, James G.
Smith, James R.
Matzuk, Martin M.
Pereira-Smith, Olivia M.
Molecular and Cellular Biology
MRG15 is a highly conserved protein, and orthologs exist in organisms from yeast to humans. MRG15 associates with at least two nucleoprotein complexes that include histone acetyltransferases and/or histone deacetylases, suggesting it is involved in chromatin remodeling. To study the role of MRG15 in vivo, we generated knockout mice and determined that the phenotype is embryonic lethal, with embryos and the few stillborn pups exhibiting developmental delay. Immunohistochemical analysis indicates that apoptosis in Mrg15−/− embryos is not increased compared with wild-type littermates. However, the number of proliferating cells is significantly reduced in various tissues of the smaller null embryos compared with control littermates. Cell proliferation defects are also observed in Mrg15−/− mouse embryonic fibroblasts. The hearts of the Mrg15−/− embryos exhibit some features of hypertrophic cardiomyopathy. The increase in size of the cardiomyocytes is most likely a response to decreased growth of the cells. Mrg15−/− embryos appeared pale, and microarray analysis revealed that α-globin gene expression was decreased in null versus wild-type embryos. We determined by chromatin immunoprecipitation that MRG15 was recruited to the α-globin promoter during dimethyl sulfoxide-induced mouse erythroleukemia cell differentiation. These findings demonstrate that MRG15 has an essential role in embryonic development via chromatin remodeling and transcriptional regulation.
Dietary restriction maintains the basal rate of somatotrope renewal in later life in male rats
We investigated the impact of dietary restriction on the basal rate of somatotrope renewal in the pituitary gland. Bromodeoxyuridine (BrdU), a thymidine analog, was administered continuously for 1 week in male F344 rats at 3, 8 and 20 months of age (mo), fed ad libitum (AL) or diet restricted from 1.5 mo (DR). Combined immunostainings for BrdU and GH visualized newly formed somatotropes as well as pituitary cells in tissue sections. The rate of incorporation of BrdU by anterior pituitary cells (BrdU-labeled nuclei/100 nuclei) was not influenced by the dietary regimen or age. The fraction of BrdU-labeled somatotropes relative to all labeled cells precipitously decreased to the same level in both dietary groups between 3 and 8 mo, although the fraction was greater in DR rats at 3 mo. In AL rats, the fraction decreased further between 8 and 20 mo, while it stabilized in DR rats. Our results suggested that dietary restriction maintains the basal rate of somatotrope renewal in later life in male rats. Although one must also estimate the effects of dietary restriction on apoptotic cell death in pituitary cells, the present study provides evidence that dietary restriction modulates somatotropes cell turnover and preserves the cell population for GH secretion during aging.
Aging; dietary restriction; somatotrope; cell renewal; growth hormone
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