Holocentric Chromosomes of Luzula elegans Are Characterized by a Longitudinal Centromere Groove, Chromosome Bending, and a Terminal Nucleolus Organizer Region

The structure of holocentric chromosomes was analyzed in mitotic cells of Luzula elegans. Light and scanning electron microscopy observations provided evidence for the existence of a longitudinal groove along each sister chromatid. The centromere-specific histone H3 variant, CENH3, colocalized with this groove and with microtubule attachment sites. The terminal chromosomal regions were CENH3-negative. During metaphase to anaphase transition, L. elegans chromosomes typically curved to a sickle-like shape, a process that is likely to be influenced by the pulling forces of microtubules along the holocentric axis towards the corresponding microtubule organizing regions. A single pair of 45S rDNA sites, situated distal to Arabidopsis-telomere repeats, was observed at the terminal region of one chromosome pair. We suggest that the 45S rDNA position in distal centromere-free regions could be required to ensure chromosome stability. Copyright (C) 2011 S. Karger AG, Base

Stretching the Rules: Monocentric Chromosomes with Multiple Centromere Domains

The centromere is a functional chromosome domain that is essential for faithful chromosome segregation during cell division and that can be reliably identified by the presence of the centromere-specific histone H3 variant CenH3. In monocentric chromosomes, the centromere is characterized by a single CenH3-containing region within a morphologically distinct primary constriction. This region usually spans up to a few Mbp composed mainly of centromere-specific satellite DNA common to all chromosomes of a given species. In holocentric chromosomes, there is no primary constriction; the centromere is composed of many CenH3 loci distributed along the entire length of a chromosome. Using correlative fluorescence light microscopy and high-resolution electron microscopy, we show that pea (Pisum sativum) chromosomes exhibit remarkably long primary constrictions that contain 3-5 explicit CenH3-containing regions, a novelty in centromere organization. In addition, we estimate that the size of the chromosome segment delimited by two outermost domains varies between 69 Mbp and 107 Mbp, several factors larger than any known centromere length. These domains are almost entirely composed of repetitive DNA sequences belonging to 13 distinct families of satellite DNA and one family of centromeric retrotransposons, all of which are unevenly distributed among pea chromosomes. We present the centromeres of Pisum as novel ``meta-polycentric'' functional domains. Our results demonstrate that the organization and DNA composition of functional centromere domains can be far more complex than previously thought, do not require single repetitive elements, and do not require single centromere domains in order to segregate properly. Based on these findings, we propose Pisum as a useful model for investigation of centromere architecture and the still poorly understood role of repetitive DNA in centromere evolution, determination, and function

Cytomolecular identification of individual wheat-wheat chromosome arm associations in wheat-rye hybrids

Chromosome pairing in the meiotic metaphase I of wheatrye hybrids has been characterized by sequential genomic and fluorescent in situ hybridization allowing not only the discrimination of wheat and rye chromosomes, but also the identification of the individual wheat and rye chromosome arms involved in the chromosome associations. The majority of associations (93.8%) were observed between the wheat chromosomes. The largest number of wheat-wheat chromosome associations (53%) was detected between the A and D genomes, while the frequency of B-D and A-B associations was significantly lower (32 and 8%, respectively). Among the A-D chromosome associations, pairing between the 3AL and 3DL arms was observed with the highest frequency, while the most frequent of all the chromosome associations (0.113/ cell) was found to be the 3DS-3BS. Differences in the pairing frequency of the individual chromosome arms of wheat-rye hybrids have been discussed in relation to the homoeologous relationships between the constituent genomes of hexaploid wheat

Tumor Necrosis Factor Alpha-Induced Interleukin-8 Production via NF- B and Phosphatidylinositol 3-Kinase/Akt Pathways Inhibits Cell Apoptosis in Human Hepatocytes

Tumor necrosis factor alpha (TNF-α) not only induces apoptotic signals but also causes antiapoptotic and regenerative responses in the liver. However, the molecular mechanism(s) of the latter events remains unclear. In the present study, we examined TNF-α-induced genes in Hc human normal (unsensitized) hepatocytes by cDNA microarray analysis. Interleukin-8 (IL-8) induction was the most pronounced of the upregulated genes. The IL-8 protein level was also increased. IL-8 belongs to the ELR-CXC chemokine family and appears to exert mitogenic and antiapoptotic functions in other cell systems. IL-8 expression by TNF-α was inhibited when two survival signals, nuclear factor κB (NF-κB) and phosphatidylinositol 3-kinase (PI3K)/Akt, were inhibited by a mutant form of inhibitor of NF-κB (IκB); by dominant negative (kinase-dead) Akt; or by treatment with LY 294002, an inhibitor of PI3K. TNF-α induced apoptosis in Hc cells that were sensitized by inhibition of NF-κB and PI3K activation. IL-8 administration protected mice against concanavalin A-induced hepatitis in vivo. IL-8 also rescued the sensitized Hc cells, at least in part, from TNF-α-induced apoptosis in vitro. TNF-α inhibited DNA synthesis in unsensitized Hc cells in the absence of serum. Exogenous IL-8 reversed, though anti-IL-8 neutralization antibody enhanced, growth inhibition by TNF-α. These results indicate that IL-8, the production of which is stimulated by TNF-α, inhibits apoptosis of sensitized hepatocytes and releases normal (unsensitized) hepatocytes from growth inhibition induced by TNF-α

An epistatic mini-circuitry between the transcription factors Snail and HNF4\uce\ub1 controls liver stem cell and hepatocyte features exhorting opposite regulation on stemness-inhibiting microRNAs

Preservation of the epithelial state involves the stable repression of epithelial-to-mesenchymal transition program, whereas maintenance of the stem compartment requires the inhibition of differentiation processes. A simple and direct molecular mini-circuitry between master elements of these biological processes might provide the best device to keep balanced such complex phenomena. In this work, we show that in hepatic stem cell Snail, a transcriptional repressor of the hepatocyte differentiation master gene HNF4\uce\ub1, directly represses the expression of the epithelial microRNAs (miRs)-200c and-34a, which in turn target several stem cell genes. Notably, in differentiated hepatocytes HNF4\uce\ub1, previously identified as a transcriptional repressor of Snail, induces the miRs-34a and-200a, b, c that, when silenced, causes epithelial dedifferentiation and reacquisition of stem traits. Altogether these data unveiled Snail, HNF4\uce\ub1 and miRs-200a, b, c and-34a as epistatic elements controlling hepatic stem cell maintenance/differentiation. \uc2\ua9 2012 Macmillan Publishers Limited. All rights reserved

Respiratory distress and perinatal lethality in Nedd4-2-deficient mice

The epithelial sodium channel (ENaC) is essential for sodium homoeostasis in many epithelia. ENaC activity is required for lung fluid clearance in newborn animals and for maintenance of blood volume and blood pressure in adults. In vitro studies show that the ubiquitin ligase Nedd4-2 ubiquitinates ENaC to regulate its cell surface expression. Here we show that knockout of Nedd4-2 in mice leads to increased ENaC expression and activity in embryonic lung. This increased ENaC activity is the likely reason for premature fetal lung fluid clearance in Nedd4-2−/− animals, resulting in a failure to inflate lungs and perinatal lethality. A small percentage of Nedd4-2−/− animals survive up to 22 days, and these animals also show increased ENaC expression and develop lethal sterile inflammation of the lung. Thus, we provide critical in vivo evidence that Nedd4-2 is essential for correct regulation of ENaC expression, fetal and postnatal lung function and animal survival

Traditional eye medicine use by newly presenting ophthalmic patients to a teaching hospital in south-eastern Nigeria: socio-demographic and clinical correlates

<p>Abstract</p> <p>Background</p> <p>This study set out to determine the incidence, socio-demographic, and clinical correlates of Traditional Eye Medicine (TEM) use in a population of newly presenting ophthalmic outpatients attending a tertiary eye care centre in south-eastern Nigeria.</p> <p>Methods</p> <p>In a comparative cross-sectional survey at the eye clinic of the University of Nigeria Teaching Hospital (UNTH), Enugu, between August 2004 - July 2006, all newly presenting ophthalmic outpatients were recruited. Participants' socio-demographic and clinical data and profile of TEM use were obtained from history and examination of each participant and entered into a pretested questionnaire and proforma. Participants were subsequently categorized into TEM- users and non-users; intra-group analysis yielded proportions, frequencies, and percentages while chi-square test was used for inter-group comparisons at P = 0.01, df = 1.</p> <p>Results</p> <p>Of the 2,542 (males, 48.1%; females, 51.9%) participants, 149 (5.9%) (males, 45%; females, 55%) used TEM for their current eye disease. The TEMs used were chemical substances (57.7%), plant products (37.7%), and animal products (4.7%). They were more often prescribed by non-traditional (66.4%) than traditional (36.9%) medicine practitioners. TEMs were used on account of vision loss (58.5%), ocular itching (25.4%) and eye discharge (3.8%). Reported efficacy from previous users (67.1%) and belief in potency (28.2%) were the main reasons for using TEM. Civil servants (20.1%), farmers (17.7%), and traders (14.1%) were the leading users of TEM. TEM use was significantly associated with younger age (p < 0.01), being married (p < 0.01), rural residence (p < 0.01), ocular anterior segment disease (p < 0.01), delayed presentation (p < 0.01), low presenting visual acuity (p < 0.01), and co-morbid chronic medical disease (p < 0.01), but not with gender (p = 0.157), and educational status (p = 0.115).</p> <p>Conclusion</p> <p>The incidence of TEM use among new ophthalmic outpatients at UNTH is low. The reasons for TEM use are amenable to positive change through enhanced delivery of promotive, preventive, and curative public eye care services. This has implications for eye care planners and implementers. To reverse the trend, we suggest strengthening of eye care programmes, even distribution of eye care resources, active collaboration with orthodox eye care providers and traditional medical practitioners, and intensification of research efforts into the pharmacology of TEMs.</p

Using Microsatellites to Understand the Physical Distribution of Recombination on Soybean Chromosomes

Soybean is a major crop that is an important source of oil and proteins. A number of genetic linkage maps have been developed in soybean. Specifically, hundreds of simple sequence repeat (SSR) markers have been developed and mapped. Recent sequencing of the soybean genome resulted in the generation of vast amounts of genetic information. The objectives of this investigation were to use SSR markers in developing a connection between genetic and physical maps and to determine the physical distribution of recombination on soybean chromosomes. A total of 2,188 SSRs were used for sequence-based physical localization on soybean chromosomes. Linkage information was used from different maps to create an integrated genetic map. Comparison of the integrated genetic linkage maps and sequence based physical maps revealed that the distal 25% of each chromosome was the most marker-dense, containing an average of 47.4% of the SSR markers and 50.2% of the genes. The proximal 25% of each chromosome contained only 7.4% of the markers and 6.7% of the genes. At the whole genome level, the marker density and gene density showed a high correlation (R2) of 0.64 and 0.83, respectively with the physical distance from the centromere. Recombination followed a similar pattern with comparisons indicating that recombination is high in telomeric regions, though the correlation between crossover frequency and distance from the centromeres is low (R2 = 0.21). Most of the centromeric regions were low in recombination. The crossover frequency for the entire soybean genome was 7.2%, with extremes much higher and lower than average. The number of recombination hotspots varied from 1 to 12 per chromosome. A high correlation of 0.83 between the distribution of SSR markers and genes suggested close association of SSRs with genes. The knowledge of distribution of recombination on chromosomes may be applied in characterizing and targeting genes