Spinal cord regeneration: Lessons for mammals from non‐mammalian vertebrates

Unlike mammals, regenerative model organisms such as amphibians and fish are capable of spinal cord regeneration after injury. Certain key differences between regenerative and nonregenerative organisms have been suggested as involved in promoting this process, such as the capacity for neurogenesis and axonal regeneration, which appear to be facilitated by favorable astroglial, inflammatory and immune responses. These traits provide a regenerative‐permissive environment that the mammalian spinal cord appears to be lacking. Evidence for the regenerative nonpermissive environment in mammals is given by the fact that they possess neural stem/progenitor cells, which transplanted into permissive environments are able to give rise to new neurons, whereas in the nonpermissive spinal cord they are unable to do so. We discuss the traits that are favorable for regeneration, comparing what happens in mammals with each regenerative organism, aiming to describe and identify the key differences that allow regeneration. This comparison should lead us toward finding how to promote regeneration in organisms that are unable to do so. genesis 51:529–544. © 2013 Wiley Periodicals, Inc.     

Holocarboxylase synthetase regulates expression of biotin transporters by chromatin remodeling events at the SMVT locus

The sodium-dependent multivitamin transporter (SMVT) is essential for mediating and regulating biotin entry into mammalian cells. In cells, biotin is covalently linked to histones in a reaction catalyzed by holocarboxylase synthetase (HCS); biotinylation of lysine 12-biotinylated histone H4 (K12Bio H4) causes gene silencing. Here, we propose a novel role for HCS in sensing and regulating levels of biotin in eukaryotic cells. We hypothesized that nuclear translocation of HCS increases in response to biotin supplementation; HCS then biotinylates histone H4 at SMVT promoters, silencing biotin transporter genes. Jurkat lymphoma cells were cultured in media containing 0.025, 0.25, or 10 nmol/l biotin. The nuclear translocation of HCS correlated with biotin concentrations in media; the relative enrichment of both HCS and K12Bio H4 at SMVT promoter 1 (but not promoter 2) increased by 91% in cells cultured in medium containing 10 nmol/l biotin compared with 0.25 nmol/l biotin. This increase of K12Bio H4 at the SMVT promoter decreased SMVT expression by up to 86%. Biotin homeostasis by HCS-dependent chromatin remodeling at the SMVT promoter 1 locus was disrupted in HCS knockdown cells, as evidenced by abnormal chromatin structure (K12Bio H4 abundance) and increased SMVT expression. The findings from this study are consistent with the theory that HCS senses biotin, and that biotin regulates its own cellular uptake by participating in HCS-dependent chromatin remodeling events at the SMVT promoter 1 locus in Jurkat cells.     

Mapping of transfer RNA genes on tobacco chloroplast DNA

Tobacco chloroplast tRNAs have been purified by two-dimensional polyacrylamide gel electrophoresis, identified by aminoacylation, labelled at their 3-end and hybridized to tobacco chloroplast DNA restriction fragments, in order to establish a tRNA gene map. These hybridization studies have revealed the localization of at least seven genes in each inverted repeat region, a minimum of 22 tRNA genes in the large single copy region and one tRNA gene in the small single copy region. Comparison of the tobacco chloroplast tRNA gene map to that of maize shows many similarities, but also some differences suggesting that DNA sequence rearrangements have occurred in the chloroplast genome during evolution.     

Epistasis between ADIPOQ rs1501299 and PON1 rs662 polymorphisms is potentially associated with the development of knee osteoarthritis

Molecular Biology Reports - Overweight produces oxidative stress (OS) on the articular cartilage, with the subsequent risk of developing knee osteoarthritis (OA). Associations between genetic...     

Oviposition Preferences of <Emphasis Type="Italic">Plutella xylostella</Emphasis> are Influenced by the Type of Plant Induction and Glucosinolate Hydrolysis Profiles

Effects of inducing plants by exposing them to insect herbivory, mechanical damage or damaged neighboring plants were evaluated on the oviposition preferences of Plutella xylostella. The role of plant genotypes differing in their glucosinolate hydrolysis profiles was also evaluated using a wild ecotype (Col-0) and a genetically modified line (tgg1tgg2) of Arabidopsis thaliana. While the Col-0 line has normal production of glucosinolate hydrolysis products, the double myrosinase knockout (tgg1tgg2) is defective in the production of these volatiles. Dual choice oviposition assays were performed using naïve P. xylostella females, and the two A. thaliana lines, which were exposed to the three types of induction treatments. Female oviposition preferences were significantly influenced by both the type of plant induction and the plant genotypes differing in their volatile profiles. Plutella xylostella females significantly preferred to oviposit on herbivore-damaged plants (versus undamaged controls) when Col-0 plants were used, but chose control plants over the double myrosinase knockout tgg1tgg2. However, plant genotype did not influence oviposition choices between plant-plant primed or mechanically damaged plants and paired undamaged controls. Given the prevalent use of genetically modified plants and the potential differences in their responses to different types of induction, these factors may be important to consider in the management of specialist pests such as the diamondback moth P. xylostella.     

Biochemical characterization of the Staphylococcus aureus PcrA helicase and its role in plasmid rolling circle replication

Previous genetic studies have suggested that a putative chromosome-encoded helicase, PcrA, is required for the rolling circle replication of plasmid pT181 in Staphylococcus aureus. We have overexpressed and purified the staphylococcal PcrA protein and studied its biochemical properties in vitro. Purified PcrA helicase supported the in vitro replication of plasmid pT181. It had ATPase activity that was stimulated in the presence of single-stranded DNA. Unlike many replicative helicases, PcrA was highly active as a 5' --> 3' helicase and had a weaker 3' --> 5' helicase activity. The RepC initiator protein encoded by pT181 nicks at the origin of replication and becomes covalently attached to the 5' end of the DNA. The 3' OH end at the nick then serves as a primer for displacement synthesis. PcrA helicase showed an origin-specific unwinding activity with supercoiled plasmid pT181 DNA that had been nicked at the origin by RepC. We also provide direct evidence for a protein-protein interaction between PcrA and RepC proteins. Our results are consistent with a model in which the PcrA helicase is targeted to the pT181 origin through a protein-protein interaction with RepC and facilitates the movement of the replisome by initiating unwinding from the RepC-generated nick.     

No Association between Personality and Candidate Gene Polymorphisms in a Wild Bird Population

Consistency of between-individual differences in behaviour or personality is a phenomenon in populations that can have ecological consequences and evolutionary potential. One way that behaviour can evolve is to have a genetic basis. Identifying the molecular genetic basis of personality could therefore provide insight into how and why such variation is maintained, particularly in natural populations. Previously identified candidate genes for personality in birds include the dopamine receptor D4 (DRD4), and serotonin transporter (SERT). Studies of wild bird populations have shown that exploratory and bold behaviours are associated with polymorphisms in both DRD4 and SERT. Here we tested for polymorphisms in DRD4 and SERT in the Seychelles warbler (Acrocephalus sechellensis) population on Cousin Island, Seychelles, and then investigated correlations between personality and polymorphisms in these genes. We found no genetic variation in DRD4, but identified four polymorphisms in SERT that clustered into five haplotypes. There was no correlation between bold or exploratory behaviours and SERT polymorphisms/haplotypes. The null result was not due to lack of power, and indicates that there was no association between these behaviours and variation in the candidate genes tested in this population. These null findings provide important data to facilitate representative future meta-analyses on candidate personality genes.     

Initial Data on the Molecular Epidemiology of Cryptosporidiosis in Lebanon

Cryptosporidium spp. represent a major public health problem worldwide and infect the gastrointestinal tract of both immunocompetent and immunocompromised persons. The prevalence of these parasites varies by geographic region, and no data are currently available in Lebanon. To promote an understanding of the epidemiology of cryptosporidiosisin this country, the main aim of this study was to determine the prevalence Cryptosporidium in symptomatic hospitalized patients, and to analyze the genetic diversity of the corresponding isolates. Fecal specimens were collected in four hospitals in North Lebanon from 163 patients (77 males and 86 females, ranging in age from 1 to 88 years, with a mean age of 22 years) presenting gastrointestinal disorders during the period July to December 2013. The overall prevalence of Cryptosporidium spp. infection obtained by modified Ziehl-Neelsen staining and/or nested PCR was 11%, and children <5 years old showed a higher rate of Cryptosporidium spp. The PCR products of the 15 positive samples were successfully sequenced. Among them, 10 isolates (66.7%) were identified as C. hominis, while the remaining 5 (33.3%) were identified as C. parvum. After analysis of the gp60 locus, C. hominis IdA19, a rare subtype, was found to be predominant. Two C. parvum subtypes were found: IIaA15G1R1 and IIaA15G2R1. The molecular characterization of Cryptosporidium isolates is an important step in improving our understanding of the epidemiology and transmission of the infection.     

LINE-1 retrotransposition events affect endothelial proliferation and migration

Long interspersed nuclear element-1 (LINE-1, L1) is a retrotransposon which affects the human genome by a variety of mechanisms. While LINE-1 expression is suppressed in the most somatic human cells, LINE-1 elements are activated in human cancer. Recently, high accumulation of LINE-1-encoded ORF1p and ORF2p in endothelial cells of mature human blood vessels was described. Here, we demonstrate that LINE-1 de novo retrotransposition events lead to a reduction of endothelial cell proliferation and migration in a porcine aortic endothelial (PAE) cell model. Cell cycle studies show a G0/G1 arrest in PAE cells harboring LINE-1 de novo retrotransposition events. Remarkably, in in situ analysis LINE-1-encoded ORF2p was not detectable in tumor blood vessels of different human organs while vascular endothelial cells of corresponding normal organs strongly expressed LINE-1 ORF2p. Quantitative RT-PCR analysis revealed that LINE-1 de novo retrotransposition influences selectively the expression of some angiogenic factors such as VEGF and Tie-2. Thus, our data suggest that LINE-1 de novo retrotransposition events might suppress angiogenesis and tumor vascularisation by reducing the angiogenic capacity of vascular endothelial cells.