A retrotransposon-derived gene, PEG10, is a novel imprinted gene located on human chromosome 7q21

A novel paternally expressed imprinted gene, PEG10 (Paternally Expressed 10), was identified on human chromosome 7q21. PEG10 is located near the SGCE (Sarcoglycan epsilon) gene, whose mouse homologue was recently shown to be imprinted. Therefore, it is highly possible that a new imprinted gene cluster exists on human chromosome 7q21. Analysis of two predicted open reading frames (ORF1 and ORF2) revealed that ORF1 and ORF2 have homology to the gag and pol proteins of some vertebrate retrotransposons, respectively. These data suggest that PEG10 is derived from a retrotransposon that was previously integrated into the mammalian genome. PEG10 is likely to be essential for understanding how exogenous genes become imprinted.     

A unified view of theta-phase coding in the entorhinal-hippocampal system

The discovery of theta-rhythm-dependent firing of rodent hippocampal neurons highlighted the functional significance of temporal encoding in hippocampal memory. However, earlier theoretical studies on this topic seem divergent and experimental implications are invariably complicated. To obtain a unified understanding of neural dynamics in the hippocampal memory, we here review recent developments in computational models and experimental discoveries on the 'theta-phase precession' of hippocampal place cells and entorhinal grid cells. We identify a theoretical hypothesis that is well supported by experimental facts; this model reveals a significant contribution of theta-phase coding to the on-line real-time operation of episodic events, through highly parallel representation of spatiotemporal information.     

Properties of α-l-iduronidase in cultured skin fibroblasts from α-l-iduronidase-deficient patients

Summary On DEAE cellulose column chromatography, -l-iduronidase in cultured skin fibroblasts was resolved into two distinct components, forms A and B. They had similar K_m values for 4-methylumbelliferyl--l-iduronide, but differed in pH optima and thermal stability. Form B was more heat-stable than form A.Residual -l-iduronidase activity in Hurler fibroblasts was heat-stable, while that in Scheie fibroblasts was heat-labile, and moreover, that in Hurler-Scheie compound fibroblasts lay intermediate between Hurler and Scheie syndromes. These findings demonstrated that Hurler syndrome, Scheie syndrome and Hurler-Scheie compound were enzymatically distinguishable.     

Molecular and Physiological Analysis of Al3+ and H+ Rhizotoxicities at Moderately Acidic Conditions

Al³⁺ and H⁺ toxicities predicted to occur at moderately acidic conditions (pH [water] = 5–5.5) in low-Ca soils were characterized by the combined approaches of computational modeling of electrostatic interactions of ions at the root plasma membrane (PM) surface and molecular/physiological analyses in Arabidopsis (Arabidopsis thaliana). Root growth inhibition in known hypersensitive mutants was correlated with computed {Al³⁺} at the PM surface ({Al3+}_PM); inhibition was alleviated by increased Ca, which also reduced {Al3+}_PM and correlated with cellular Al responses based on expression analysis of genes that are markers for Al stress. The Al-inducible Al tolerance genes ALUMINUM-ACTIVATED MALATE TRANSPORTER1 and ALUMINUM SENSITIVE3 were induced by levels of {Al3+}_PM too low to inhibit root growth in tolerant genotypes, indicating that protective responses are triggered when {Al3+}_PM was below levels that can initiate injury. Modeling of the H⁺ sensitivity of the SENSITIVE TO PROTON RHIZOTOXICITY1 knockout mutant identified a Ca alleviation mechanism of H⁺ rhizotoxicity, possibly involving stabilization of the cell wall. The phosphatidate phosphohydrolase1 (pah1) pah2 double mutant showed enhanced Al susceptibility under low-P conditions, where greater levels of negatively charged phospholipids in the PM occur, which increases {Al3+}_PM through increased PM surface negativity compared with wild-type plants. Finally, we found that the nonalkalinizing Ca fertilizer gypsum improved the tolerance of the sensitive genotypes in moderately acidic soils. These findings fit our modeling predictions that root toxicity to Al³⁺ and H⁺ in moderately acidic soils involves interactions between both toxic ions in relation to Ca alleviation.Aluminum (Al), principally in the form of Al³⁺ released from soil clay minerals, is one of the most important rhizotoxic ions in acidic soils and is abundant in soil solutions at pH (water) of less than 5.0. Many forest and grass land species naturally adapted to acid soils are very tolerant of H⁺ and Al³⁺ and thrive in soils where the pH is less than 4.0. However, most crop plants used for agriculture show inhibitory growth effects, even when the soil pH is neutralized by liming to moderately acidic pH values in the range of pH 5 to 5.5. For example, crops sensitive to Al³⁺ and H⁺ such as turnip (Brassica rapa; Kinraide and Parker, 1990) and alfalfa (Medicago sativa; Yokota and Ojima, 1995) show growth inhibition at these soil pH values. Field research and soil experiments have shown that inhibitory effects of moderately acidic soils (pH > 5) can be ameliorated by the application of Ca fertilizers, even if they are nonalkalinizing, such as gypsum, and this leads to improvement in crop productivity (Carvalho and Van Raij, 1997; Mora et al., 1999). This indicates that the soil Ca status is an important factor in determining crop yield at moderately low soil pH values with regard to Al³⁺ and H⁺ rhizotoxicity occurring in these soils. An understanding of the complex situation of acid soil stress in soil pH in the range of pH (water) 5 to 5.5 is important for designing efficient soil acidity management and breeding programs for resistant crop use in low-input agricultural systems.The complex rhizotoxicities at moderately acidic conditions that can be alleviated by Ca have been predicted by modeling studies in wheat (Triticum aestivum; Kinraide, 2003). The model first computes the activity of the rhizotoxicants and alleviants at the plasma membrane (PM) surface, for example {Al3+}_PM and {H+}_PM, and {Ca2+}_PM, using a speciation-based Gouy-Chapman-Stern electrostatic (SGCS) model (Kinraide and Wang, 2010). The mechanisms of toxicity and alleviation are then modeled by regression analyses for root growth inhibition fitted to the nonlinear equations (Kinraide, 2003; Kinraide et al., 2004). The modeling studies well describe the complicated events in the Al-toxic solutions near the PM surface under moderately acidic conditions. For example, the elevation of pH from 4.5 to between 5 and 5.5 decreases the activity of the most rhizotoxic Al species, Al³⁺ in the solution ({Al3+}_bulk), while it increases the negativity of the PM surface because of dissociation of H⁺ from potentially negative ligands such as phospholipids. As a result, {Al3+}_PM remains at moderately high levels at the PM surface at pH greater than 5 due to the attraction to negative charges on the PM surface, but it can be alleviated by coexisting cations such as Ca²⁺ and even by another rhizotoxic cation, H⁺. These modeling studies have proposed different mechanisms of Ca alleviation in this complex situation (Kinraide, 1998; Kinraide et al., 2004). Mechanisms I (the electrostatic displacement of toxicant at the PM surface) and II (the restoration at the PM surface of Ca²⁺ electrostatically displaced by the toxicant) are events at the PM surface, but mechanism III, which explains the remaining portion of the Ca alleviation, may involve other physiological responses, including unknown mechanisms. These predictions, derived from the modeling study, likely explain the complex nature of moderately acidic soils but may require further validation because they were developed using root growth as the sole criterion for rhizotoxicity.Although these types of modeling approaches have not been performed using Arabidopsis (Arabidopsis thaliana) plants, clear symptoms of Al³⁺ and H⁺ rhizotoxicity at moderately acidic conditions (pH ≥ 5) has been identified in Arabidopsis (Kobayashi and Koyama, 2002; Iuchi et al., 2007). A quantitative trait locus study of Al tolerance at moderately acidic conditions (4 μm Al, pH 5; Kobayashi and Koyama, 2002) identified a very similar genetic architecture of Al tolerance to that derived from a study that employed a lower pH value but with a greater level of Al (50 μm Al, pH 4.2; Hoekenga et al., 2003). The former conditions employed a lower Ca concentration (200 μm) than the latter (3 mm), which accounted for the predictions of {Al3+}_PM in relation to {Ca2+}_PM by electrostatics. On the other hand, several Al³⁺- and H⁺-sensitive transfer DNA insertion knockout (KO) mutant genotypes have been identified using the lower ionic-strength moderately acidic media (Sawaki et al., 2009). These lines exhibit different degrees of hypersensitivity to moderately acidic conditions because of the dysfunction of different tolerance genes, suggesting the involvement of different mechanisms. In Arabidopsis, ALUMINUM-ACTIVATED MALATE TRANSPORTER1 (AtALMT1) regulates Al-activated root malate excretion that protects the root tip from acute Al toxicity by Al exclusion (Hoekenga et al., 2006), and ALUMINUM SENSITIVE3 (ALS3) regulates internal Al sequestration involved in long term Al tolerance (Larsen et al., 1997, 2005). The KO mutants for these genes display Al hypersensitivity. In addition, SENSITIVE TO PROTON RHIZOTOXICITY1 (STOP1)-KO, a suppressor of multiple genes for Al and H⁺ tolerance, shows sensitivity to Al³⁺ and H⁺ (Iuchi et al., 2007; Sawaki et al., 2009). These sensitive genotypes are useful tools for evaluating Al³⁺ and H⁺ toxicity in the pH range 5 to 5.5. On the other hand, several cellular responses, such as the induction of gene expression, have been identified in Arabidopsis that could be useful in the estimation of the attraction of {Al³⁺} to the PM, which is computed by our electrostatic-based model. Therefore, Arabidopsis appears to be a useful model system for the validation of modeling based on the SGCS model and to further our understanding of Al³⁺ and H⁺ rhizotoxicities at moderately acidic conditions in relation to Ca²⁺ alleviation.Computation of {Al3+}_PM requires accurate speciation of Al and other solutes in the bulk solution. The original SGCS program is suitable for relatively simple solutions (Kinraide and Wang, 2010). However, the rooting medium used for the Arabidopsis assays exceeds the number of solutes that can be accurately assessed by the SGCS program (Kobayashi et al., 2007). Consequently, we updated the modeling methodology using the speciation program GEOCHEM-EZ, which is suitable for complex media (Famoso et al., 2010; Shaff et al., 2010). This improved model, used in conjunction with molecular biological assays such as biomarker analysis of Al-inducible gene expression, has allowed us in this study to validate the predicted {Al3+}_PM rhizotoxicity in relation to {Ca2+}_PM alleviation from the wheat modeling studies. The updated modeling of Ca alleviation in mutants uncovered one of the mechanisms of Ca alleviation in the H⁺-sensitive mutant and identified an Al-sensitive double mutant genotype, phosphatidate phosphohydrolase1 (pah1) and pah2 (Nakamura et al., 2009), that fitted previous predictions. Finally, we demonstrate the ability of gypsum to ameliorate the sensitive phenotype of selected genotypes, when they were grown in moderately acidic soil culture. Taken together, we present here experimental validation of the SGCS-based modeling, and its combination with molecular physiology provides a deeper understanding of plant Al³⁺ and H⁺ toxicity in relation to Ca²⁺ alleviation at pΗ of at least 5.0.     

Identification of a new IgE-binding epitope of peanut oleosin that cross-reacts with buckwheat

Peanut and buckwheat induce a severe allergic reaction, anaphylaxis, which is considered to be mediated by immunoglobulin E (IgE). We identified in this study a new IgE-binding epitope of the peanut allergen that cross-reacted with buckwheat. The phosphate-buffered saline-soluble fraction of buckwheat inhibited the binding between IgE and the peanut allergen. A cross-reactive peptide was isolated from the α-chymotrypsin hydrolysate of peanut. Based on the amino acid sequence and mass spectrometric analysis data, the peptide was identified as Ser-Asp-Gln-Thr-Arg-Thr-Gly-Tyr (SDQTRTGY); this sequence is identical to amino acids 2-9 in the N-terminal hydrophilic domain of oleosin 3 which is located on the surface of the lipid storage body. Synthetic SDQTRTGY was found to bind with IgE in the sera of all eight peanut-allergic patients tested. Since many foods of plant origin contain oleosin, the possibility of an anaphylactic cross-reaction in allergic patients should always be considered.