Transgenic tomato plants expressing an <Emphasis Type="Italic">Arabidopsis</Emphasis> thionin (<Emphasis Type="Italic">Thi2.1</Emphasis>) driven by fruit-inactive promoter battle against phytopathogenic attack

Tomato is one of the most important crop plants; however, attacks by pathogens can cause serious losses in production. In this report, we explore the potential of using the Arabidopsis thionin (Thi2.1) gene to genetically engineer enhanced resistance to multiple diseases in tomato. Potential thionin toxicity in fruits was negated by the use of a fruit-inactive promoter to drive the Thi2.1 gene. In transgenic lines containing RB7/Thi2.1, constitutive Thi2.1 expression was detected in roots and incidentally in leaves, but not in fruits. Disease assays revealed that the transgenic lines that were tested conferred significant levels of enhanced resistance to bacterial wilt (BW) and Fusarium wilt (FW). Further studies indicated that BW disease progression in transgenic lines was delayed by a systemic suppression of bacterial multiplication. By adopting a safe genetic engineering strategy, the present investigation is another step forward demonstrating thionin practicality in crop protection.     

Arsenic trioxide represses constitutive activation of NF-kappaB and COX-2 expression in human acute myeloid leukemia, HL-60

It has been proposed that eukaryotic nuclear factor nuclear factor kappa-B (NF-kappaB) and cyclooxygenase-2 (COX-2) are implicated in the pathogenesis of many human diseases including cancer. Arsenic has been widely used in medicine in Oriental countries. Recent studies have shown that arsenic trioxide (As(2)O(3)) could induce in vitro growth inhibition and apoptosis of malignant lymphocytes, and myeloma cells. However, the molecular mechanisms by which As(2)O(3) initiates cellular signaling toward cell death are still unclear. In the present study, the effects of As(2)O(3) on NF-kappaB and COX-2 expression in HL-60 cells were investigated. As(2)O(3) suppressed DNA-binding activity of NF-kappaB composed of p65/p50 heterodimer through preventing the degradation of IkappaB-alpha and the nuclear translocation of p65 subsequently as well as interrupting the binding of NF-kappaB with their consensus sequences. Inhibitory effect of As(2)O(3) on NF-kappaB DNA activity was dependent upon intracellular glutathione (GSH) and H(2)O(2) level, but not superoxide anion. Futhermore, we found that As(2)O(3) also downregulated the expression of COX-2, which has NF-kappaB binding site on its promoter through repressing the NF-kappaB DNA-binding activity.     

A population-based LD map of the human chromosome 6p

The recent publication of the complete sequence of human chromosome 6 provides a platform from which to investigate genomic sequence variation. We report here a detailed linkage disequilibrium (LD) pattern map across the entire human chromosome 6p by using a set of 1152 single nucleotide polymorphisms (SNPs) in a population of 198 Singaporean Chinese, with 326 SNPs focused in the major histocompatibility complex (MHC) region. Our analysis shows some unexpectedly high segments of strong LD in a 10-Mb region that includes the extremely polymorphic and gene-rich MHC loci and many non-MHC genes. These include the telomeric peri-MHC region that harbors olfactory receptors, histones and zinc finger clusters, and the centromeric peri-MHC region that contains several unknown open reading frames. The data also help refine a human–mouse synteny break in the region between 28.6 and 29.4 Mb. The population-based LD map presented here will provide an essential resource for understanding the genomic sequence variation of chromosome 6p and LD mapping of disease genes of complex genetic traits. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users. H. Yu and J.-M. Chia should be regarded as joint first authors.     

Metabolic syndrome and type 2 diabetes: the Hong Kong perspective

The Metabolic syndrome (MetS), obesity and type 2 diabetes are growing global epidemics especially in Asian populations. In light of the differences in body build between people from the West and the East, definitions of obesity in Asians have been modified accordingly. Data from Hong Kong, an epitome of future China, may provide important insight into the potential interactions between nature and nurture in this global epidemic. Now supported by large scale studies, it is clear that Chinese type 2 diabetic patients exhibit marked phenotypic heterogeneity in terms of risk profiles and complications. Apart from genetic differences, age- and stress-related neurohormonal dysregulation may also contribute to the increasing prevalence of obesity, type 2 diabetes and MetS in Chinese living in modern societies. In this mini-review, we aim to summarise findings from our group collected during the last decade in our attempt to understand this epidemic and to develop evidence-based care models to reduce the impact of this health hazard.     

Spatial distribution of lead in enamel and coronal dentine of wistar rats

Lead is one of the most hazardous environmental toxins known. The assessment of lead in dental hard tissues is important in the understanding of its toxic effects on oral tissues and in estimating exposure and body burden in individuals exposed to lead from the environment. However, current information on the uptake and distribution of lead in enamel and dentine is limited. The aim of this project was to study, at high resolution, the spatial distribution of lead in enamel and coronal dentine using an experimental rat model. A dose of 40 mg/L of lead nitrate was administered to pregnant female rats during the periods of gestation and lactation through drinking water. First mandibular molar teeth were removed from their 15-d-old pups and the distribution of lead was studied using a nuclear microprobe (NMP). The distribution of lead in enamel and coronal dentine showed four distinct zones with significantly different mean lead concentrations (p<0.05). High levels of lead were observed in the superficial regions of enamel and in the dentine directly adjacent to the pulp. Additionally, the results confirmed that the NMP is capable of mapping the distribution of lead in teeth at micron resolutions with a detection limit of approx 1 microg/g.     

The effects of phenytoin and its metabolite 5-(4-hydroxyphenyl)-5-phenylhydantoin on cellular glucose transport

Glucose is the principal fuel for brain metabolism and its movement across the blood-brain barrier depends on Glut1. Impaired glucose transport to the brain may have deleterious consequences. For example, Glut1 deficiency syndrome (Glut1DS) is the result of heterozygous loss of function Glut1 mutation leading to energy failure of the brain and subsequently, epileptic encephalopathy. To preserve the integrity of the energy supply to the brain in patients with compromised glucose transport function, consumption of compounds with glucose transport inhibiting properties should be avoided. Phenytoin is a widely used anticonvulsant that affects carbohydrate metabolism. In this study, the hypothesis that phenytoin and its metabolite 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH) affect cellular glucose transport was tested. With a focus on Glut1, the effects of phenytoin and HPPH on cellular glucose transport were studied. Glucose uptake assay measuring the zero-trans influx of radioactive-labeled glucose analogues showed that phenytoin and HPPH did not exert immediate effects on erythrocyte Glut1 activity or glucose transport in Hs68 control fibroblasts, Glut1DS primary fibroblasts isolated from two patients, or in rat primary astrocytes. Prolonged exposure to the two compounds could stimulate glucose transport by up to 30-60% over the control level (p <0.05) in Hs68 and Glut1DS fibroblasts as well as in rat astrocytes. The stimulation of glucose transport by HPPH was dose-dependent and accompanied by an up-regulation of GLUT1 mRNA expression (p <0.05). In conclusion, phenytoin and HPPH do not compromise cellular glucose transport. Prolonged exposure to these compounds can modify carbohydrate homeostasis by up-regulating glucose transport in both normal and Glut1DS conditions in vitro.     

Localization of the microtubule end binding protein EB1 reveals alternative pathways of spindle development in Arabidopsis suspension cells

In a previous study on Arabidopsis thaliana suspension cells transiently infected with the microtubule end binding protein AtEB1a-green fluorescent protein (GFP), we reported that interphase microtubules grow from multiple sites dispersed over the cortex, with plus ends forming the characteristic comet-like pattern. In this study, AtEB1a-GFP was used to study the transitions of microtubule arrays throughout the division cycle of cells lacking a defined centrosome. During division, the dispersed origin of microtubules was replaced by a more focused pattern with the plus end comets growing away from sites associated with the nuclear periphery. The mitotic spindle then evolved in two quite distinct ways depending on the presence or absence of the preprophase band (PPB): the cells displaying outside-in as well as inside-out mitotic pathways. In those cells possessing a PPB, the fusion protein labeled material at the nuclear periphery that segregated into two polar caps, perpendicular to the PPB, before nuclear envelope breakdown (NEBD). These polar caps then marked the spindle poles upon NEBD. However, in the population of cells without PPBs, there was no prepolarization of material at the nuclear envelope before NEBD, and the bipolar spindle only emerged clearly after NEBD. Such cells had variable spindle orientations and enhanced phragmoplast mobility, suggesting that the PPB is involved in a polarization event that promotes early spindle pole morphogenesis and subsequent positional stability during division. Astral-like microtubules are not usually prominent in plant cells, but they are clearly seen in these Arabidopsis cells, and we hypothesize that they may be involved in orienting the division plane, particularly where the plane is not determined before division.     

Stat3 links activated keratinocytes and immunocytes required for development of psoriasis in a novel transgenic mouse model

Here we report that epidermal keratinocytes in psoriatic lesions are characterized by activated Stat3. Transgenic mice with keratinocytes expressing a constitutively active Stat3 (K5.Stat3C mice) develop a skin phenotype either spontaneously, or in response to wounding, that closely resembles psoriasis. Keratinocytes from K5.Stat3C mice show upregulation of several molecules linked to the pathogenesis of psoriasis. In addition, the development of psoriatic lesions in K5.Stat3C mice requires cooperation between Stat3 activation in keratinocytes and activated T cells. Finally, abrogation of Stat3 function by a decoy oligonucleotide inhibits the onset and reverses established psoriatic lesions in K5.Stat3C mice. Thus, targeting Stat3 may be potentially therapeutic in the treatment of psoriasis.     

Amelioration of inflammatory arthritis by targeting the pre-ligand assembly domain of tumor necrosis factor receptors

Tumor necrosis factor (TNF)-alpha has an important role in the pathogenesis of autoimmune and inflammatory diseases such as rheumatoid and septic arthritis. The biological effects of TNF-alpha are mediated by binding to TNF receptors TNFR1 (also known as P60) or TNFR2 (also known as P80). The pre-ligand assembly domain (PLAD) is a portion of the extracellular region of TNFRs that mediates receptor-chain association essential for signaling. We found that soluble versions of PLAD, especially those derived from P60, block the biochemical effects of TNF-alpha in vitro and potently inhibit arthritis in animal models. Thus, targeting the PLAD may have clinical value in the treatment of human arthritis and other disorders involving receptors of the TNFR superfamily.     

Migration and differentiation of neural precursors derived from human embryonic stem cells in the rat brain

Human embryonic stem (hES) cells provide a potentially unlimited cell source for regenerative medicine. Recently, differentiation strategies were developed to direct hES cells towards neural fates in vitro. However, the interaction of hES cell progeny with the adult brain environment remains unexplored. Here we report that hES cell-derived neural precursors differentiate into neurons, astrocytes and oligodendrocytes in the normal and lesioned brain of young adult rats and migrate extensively along white matter tracts. The differentiation and migration behavior of hES cell progeny was region specific. The hES cell-derived neural precursors integrated into the endogenous precursor pool in the subventricular zone, a site of persistent neurogenesis. Like adult neural stem cells, hES cell-derived precursors traveled along the rostral migratory stream to the olfactory bulb, where they contributed to neurogenesis. We found no evidence of cell fusion, suggesting that hES cell progeny are capable of responding appropriately to host cues in the subventricular zone.