Mutations in the polyglutamine binding protein 1 gene cause X-linked mental retardation

We found mutations in the gene PQBP1 in 5 of 29 families with nonsyndromic (MRX) and syndromic (MRXS) forms of X-linked mental retardation (XLMR). Clinical features in affected males include mental retardation, microcephaly, short stature, spastic paraplegia and midline defects. PQBP1 has previously been implicated in the pathogenesis of polyglutamine expansion diseases. Our findings link this gene to XLMR and shed more light on the pathogenesis of this common disorder.     

Nonmuscle myosin-2: mix and match

Members of the nonmuscle myosin-2 (NM-2) family of actin-based molecular motors catalyze the conversion of chemical energy into directed movement and force thereby acting as central regulatory components of the eukaryotic cytoskeleton. By cyclically interacting with adenosine triphosphate and F-actin, NM-2 isoforms promote cytoskeletal force generation in established cellular processes like cell migration, shape changes, adhesion dynamics, endo- and exo-cytosis, and cytokinesis. Novel functions of the NM-2 family members in autophagy and viral infection are emerging, making NM-2 isoforms regulators of nearly all cellular processes that require the spatiotemporal organization of cytoskeletal scaffolding. Here, we assess current views about the role of NM-2 isoforms in these activities including the tight regulation of NM-2 assembly and activation through phosphorylation and how NM-2-mediated changes in cytoskeletal dynamics and mechanics affect cell physiological functions in health and disease.     

A paleoecologic perspective on past plant invasions in Yellowstone

The role of climate and natural disturbance in the past provides a context for understanding present and future changes in biota. The vegetation history of the Yellowstone region, like that of North America as a whole, is largely one of plant invasions and extinctions in response to changes in climate and environment. When Holocene plant migrations are examined on multiple spatial and temporal scales, several generalities are apparent. First, at a continental and regional scale, plant migration patterns followed the direction of climate change, whereas at local scales plant colonization was governed by site-specific conditions and possibly by biotic interactions. Second, species were individualistic in their response to climate change, and, as their ranges shifted across the landscape, existing communities were dismantled and new ones were formed. Individual species met little resistance from existing communities. Third, rates of species invasion were astonishingly rapid, suggesting that rare long-distance dispersal events were critical. Fourth, fire during periods of climate change was an important catalyst in allowing the invasion of new species, but it is unlikely that a single fire event triggered irreversible vegetation change. Regional climate and biotic changes in response to projected increases in atmospheric CO 2 in the next century suggest an even more complex picture than in the past. Model simulations portray changes in temperature and precipitation in the Yellowstone region that have not occurred in the last 20,000 years. Likewise, projected changes in species ranges, including latitudinal, longitudinal, and elevational shifts, require faster rates than anything observed in the fossil record. Increased fire occurrence may help maintain some native taxa but promote the decline of others. Thus, future conditions are likely to create evermore opportunities for exotic species to invade and establish within the Yellowstone region.     

Action Research: Its Role in the University/Business Relationship

The Action Research (AR) PhD program at Monash University had its genesis in Systems Thinking and Organizational Learning. This paper discusses the role of the university in AR projects in business and the central role that AR projects can have in a Faculty's strategic positioning. The issues that have emerged in the project to date are discussed.     

Growth mechanisms of Ag and Cu nanodendrites via Galvanic replacement reactions

Dendritic silver and copper crystals were produced via Galvanic replacement reactions on zinc and aluminum plates, respectively. The growth orientations of these metals were determined using electron microscopy. The results showed that a fast crystal growth associated with a high concentration of metal cations led to kinetically controlled growth along the <112> axes of the cubic close-packed structures. However, a slow growth rate resulted in thermodynamically controlled growth along the [111] axis. The crystal growth was not found to rely upon the direct deposition of metal cations at crystallographic sites on crystal facets, but instead, hydrated metal cations deposited on the crystal surface to form an amorphous coating layer, followed by the reduction of metal cations and crystallization at the crystal/coating interface. Twin defects and stacking faults were often observed across the whole particle and commonly observed ?{422} diffraction spots were explained by stacking faults rather than by the possible presence of any superstructures. The present work offers evidences to claim that both the crystal growth rate and Coulomb interaction between negatively charged crystal surface and metal cations play an important role in the formation of metal dendrites in replacement reactions.     

Age des halos pléochroïques de la granodiorite de Lausitz

Summary By a quantitative study of pleochroic haloes in biotite, the haloe age of the Lausitz granodiorite, in comparison with the granite age of the Elba Isle, was estimated to 280±150 M.Y. The granodiorite is either caledonian or hercynian.

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Attachée à l'Institut Interuniversitaire des Sciences Nucléaires.     

Population structure, differential bias and genomic control in a large-scale, case-control association study

The main problems in drawing causal inferences from epidemiological case-control studies are confounding by unmeasured extraneous factors, selection bias and differential misclassification of exposure. In genetics the first of these, in the form of population structure, has dominated recent debate. Population structure explained part of the significant +11.2% inflation of test statistics we observed in an analysis of 6,322 nonsynonymous SNPs in 816 cases of type 1 diabetes and 877 population-based controls from Great Britain. The remainder of the inflation resulted from differential bias in genotype scoring between case and control DNA samples, which originated from two laboratories, causing false-positive associations. To avoid excluding SNPs and losing valuable information, we extended the genomic control method by applying a variable downweighting to each SNP.     

Apoptosis induced by vitamin A signaling is crucial for connecting the ureters to the bladder

Removal of toxic substances from the blood depends on patent connections between the kidney, ureters and bladder that are established when the ureter is transposed from its original insertion site in the male genital tract to the bladder. This transposition is thought to occur as the trigone forms from the common nephric duct and incorporates into the bladder. Here we re-examine this model in the context of normal and abnormal development. We show that the common nephric duct does not differentiate into the trigone but instead undergoes apoptosis, a crucial step for ureter transposition controlled by vitamin A-induced signals from the primitive bladder. Ureter abnormalities occur in 1-2% of the human population and can cause obstruction and end-stage renal disease. These studies provide an explanation for ureter defects underlying some forms of obstruction in humans and redefine the current model of ureter maturation.     

The genome sequence of the rice blast fungus Magnaporthe grisea

Magnaporthe grisea is the most destructive pathogen of rice worldwide and the principal model organism for elucidating the molecular basis of fungal disease of plants. Here, we report the draft sequence of the M. grisea genome. Analysis of the gene set provides an insight into the adaptations required by a fungus to cause disease. The genome encodes a large and diverse set of secreted proteins, including those defined by unusual carbohydrate-binding domains. This fungus also possesses an expanded family of G-protein-coupled receptors, several new virulence-associated genes and large suites of enzymes involved in secondary metabolism. Consistent with a role in fungal pathogenesis, the expression of several of these genes is upregulated during the early stages of infection-related development. The M. grisea genome has been subject to invasion and proliferation of active transposable elements, reflecting the clonal nature of this fungus imposed by widespread rice cultivation.