Mutations in genes encoding subunits of RNA polymerases I and III cause Treacher Collins syndrome

We identified a deletion of a gene encoding a subunit of RNA polymerases I and III, POLR1D, in an individual with Treacher Collins syndrome (TCS). Subsequently, we detected 20 additional heterozygous mutations of POLR1D in 252 individuals with TCS. Furthermore, we discovered mutations in both alleles of POLR1C in three individuals with TCS. These findings identify two additional genes involved in TCS, confirm the genetic heterogeneity of TCS and support the hypothesis that TCS is a ribosomopathy.     

Microdeletion encompassing MAPT at chromosome 17q21.3 is associated with developmental delay and learning disability

Recently, the application of array-based comparative genomic hybridization (array CGH) has improved rates of detection of chromosomal imbalances in individuals with mental retardation and dysmorphic features. Here, we describe three individuals with learning disability and a heterozygous deletion at chromosome 17q21.3, detected in each case by array CGH. FISH analysis demonstrated that the deletions occurred as de novo events in each individual and were between 500 kb and 650 kb in size. A recently described 900-kb inversion that suppresses recombination between ancestral H1 and H2 haplotypes encompasses the deletion. We show that, in each trio, the parent of origin of the deleted chromosome 17 carries at least one H2 chromosome. This region of 17q21.3 shows complex genomic architecture with well-described low-copy repeats (LCRs). The orientation of LCRs flanking the deleted segment in inversion heterozygotes is likely to facilitate the generation of this microdeletion by means of non-allelic homologous recombination.     

Role of AGC kinases in plant growth and stress responses

AGC kinases are important regulators of cell growth, metabolism, division, and survival in mammalian systems. Mutation or deregulation of members of this family of protein kinases contribute to the pathogenesis of many human diseases, including cancer and diabetes. Although AGC kinases are conserved in the plant kingdom, little is known about their molecular functions and targets. Some of the best-studied plant AGC kinases mediate auxin signaling and are thereby involved in the regulation of growth and morphogenesis. Furthermore, certain members are regulated by lipid-derived signals via the 3-phosphoinositide-dependent kinase 1 (PDK1) and the kinase target of rapamycin (TOR), similar to its animal counterparts. In this review, we discuss recent findings on plant AGC kinases that unravel important roles in the regulation of plant growth, immunity and cell death, and connections to stress-induced mitogen-activated protein kinase signaling cascades.     

A reduction of mitochondrial DNA molecules during embryogenesis explains the rapid segregation of genotypes

Mammalian mitochondrial DNA (mtDNA) is inherited principally down the maternal line, but the mechanisms involved are not fully understood. Females harboring a mixture of mutant and wild-type mtDNA (heteroplasmy) transmit a varying proportion of mutant mtDNA to their offspring. In humans with mtDNA disorders, the proportion of mutated mtDNA inherited from the mother correlates with disease severity. Rapid changes in allele frequency can occur in a single generation. This could be due to a marked reduction in the number of mtDNA molecules being transmitted from mother to offspring (the mitochondrial genetic bottleneck), to the partitioning of mtDNA into homoplasmic segregating units, or to the selection of a group of mtDNA molecules to re-populate the next generation. Here we show that the partitioning of mtDNA molecules into different cells before and after implantation, followed by the segregation of replicating mtDNA between proliferating primordial germ cells, is responsible for the different levels of heteroplasmy seen in the offspring of heteroplasmic female mice.     

Gastropod shell utilisation pattern by the hermit crab Clibanarius symmetricus (Anomura: Diogenidae) in an Equatorial Amazon estuary

Clibanarius symmetricus is a diogenid hermit crab that is highly abundant in rocky intertidal environments, including the rock outcrops of Amazon estuaries. This study characterises the C. symmetricus shell utilisation pattern in the Marapanim River estuary, Pará, Equatorial Amazon, based on the hypothesis that occupancy patterns would differ, in relation to biometry and diversity of occupied shells, from those of other regions in the range of this species due to the distinct and unique environmental characteristics of equatorial estuaries. Monthly samplings were carried out from August 2006 to July 2007, in the upper and lower areas of the mid-littoral during low tides. A total of seven gastropod species were found as shells occupied by hermit crabs: 93.33% were Thaisella trinitatensis shells, 2.00% Nassarius vibex, 2.00% Neritina virginea, 1.33% Natica marochiensis, 0.67% Parvanachis obesa, and, occasionally, Littorina flava and Phalium granulatum shells, each with only one occurrence (0.33%). Juveniles [cephalothoracic shield length (CL) of less than 3.6 mm] occupied a higher variety of shells, while adults occupied shells with larger meristic variation. Males occupied larger shells. The length of the animal was influenced by shell measurements (total width, aperture width and weight). Clibanarius symmetricus showed occupancy patterns generally similar to those of specimens of the same species previously studied in the Brazilian subtropical region, and this occupancy is explained by shell availability, shell size and weight, and hermit size. However, this study showed lower occupied shell species diversity, and the species with highest occupancy frequency (T. trinitatensis) was not reported in any previous studies on this hermit crab. In addition, the studied population differed in occupancy patterns, with differences between males and females, and between juveniles and adults.     

Erythropoietin formation during hypoxia in mice with impaired responsiveness to erythropoietin induced by irradiation or 5-fluorouracil injection

Summary Plasma erythropoietin levels during continuous exposure to hypobaric hypoxia in mice with marrow aplasia induced by whole body X-irradiation or 5-fluorouracil injection were higher than in control mice similarly exposed. These findings give support to the hypothesis that a relationship exists between erythropoietin production rate and erythroid responsiveness to the hormone.Supported by Conicet and Subcyt grants. Request for reprints should be addressed to C. E. B.     

Hierarchical self-assembly of metal nanostructures on diblock copolymer scaffolds.

Self-assembly is emerging as an elegant, 'bottom-up' method for fabricating nanostructured materials. This approach becomes particularly powerful when the ease and control offered by the self-assembly of organic components is combined with the electronic, magnetic or photonic properties of inorganic components. Here we demonstrate a versatile hierarchical approach for the assembly of organic-inorganic, copolymer-metal nanostructures in which one level of self-assembly guides the next. In a first step, ultrathin diblock copolymer films form a regular scaffold of highly anisotropic, stripe-like domains. During a second assembly step, differential wetting guides diffusing metal atoms to aggregate selectively along the scaffold, producing highly organized metal nanostructures. We find that, in contrast to the usual requirement of near-equilibrium conditions for ordering, the metal arranged on the copolymer scaffold produces the most highly ordered configurations when the system is far from equilibrium. We delineate two distinct assembly modes of the metal component-chains of separate nanoparticles and continuous wires-each characterized by different ordering kinetics and strikingly different current-voltage characteristics. These results therefore demonstrate the possibility of guided, large-scale assembly of laterally nanostructured systems.     

Combining Economic Forecasts by Using a Maximum Entropy Econometric Approach

This paper explores the use of a maximum entropy econometric approach to combine forecasts when the small amount of information available does not allow the use of regression procedures since a dimensionality problem arises. This approach has its roots in information theory and builds on the entropy information measures and the classical maximum entropy principle, which was developed to recover information from underdetermined models. More specifically, we use the maximum entropy econometric approach for the measure of Shannon and we also propose its extension to the quadratic uncertainty measure. The experimental results over a pool of forecasts referring to Spanish inflation show some improvements when compared with equally weighted combined forecasting. Copyright © 2011 John Wiley & Sons, Ltd.