Manipulating the Xenopus genome with transposable elements

The study of amphibian embryogenesis has provided important insight into the mechanisms of vertebrate development. The frog Xenopus laevis has been an important model of vertebrate cell biology and development for many decades. Genetic studies in this organism are not practical because of the tetraploid nature of the genome and the long generation time of this species. Recently, a closely related frog, namely Xenopus tropicalis, has been proposed as an alternative system; it shares all of the physical characteristics that make X. laevis a useful model but has the advantage of a diploid genome and short generation time. The rapid accumulation of genetic resources for this animal and the success of pilot mutagenesis screens have helped propel this model system forward. Transposable elements will provide invaluable tools for manipulating the frog genome. These integration systems are ideally suited to transgenesis and insertional mutagenesis strategies in the frog. The high fecundity of the frog combined with the ability to remobilize transposon transgenes integrated into frog genome will allow large-scale insertional mutagenesis screens to be performed in laboratories with modest husbandry capacities

Using minidrones to teach geospatial technology fundamentals

With an increased level of interest in promoting science, technology, engineering, and maths (STEM) careers, there are many ways in which drone and geospatial technology can be brought into the education system to train the future workforce. Indeed, state-level government policies are even stipulating that they should be integrated into curriculum. However, in some cases, drones may be seen as the latest toy advertised to achieve an education outcome. Some educators find it difficult to incorporate the technology in a meaningful way into their classrooms. Further, educators can often struggle to maintain currency on rapidly developing technology, particularly when it is outside of their primary area of expertise as is frequently the case in schools. Here, we present a structured approach to using drones to teach fundamental geospatial technology concepts within a STEM framework across primary/elementary, middle, secondary, and tertiary education. After successfully working with more than 6000 participants around the world, we encourage other scientists and those in industry using drones as part of their research or operations to similarly reach out to their local community to help build a diverse and strong STEM workforce of the future

Francisella tularensis: an arthropod-borne pathogen

Arthropod transmission of tularemia occurs throughout the northern hemisphere. Few pathogens show the adaptability of Francisella tularensis to such a wide array of arthropod vectors. Nonetheless, arthropod transmission of F. tularensis was last actively investigated in the first half of the 20th century. This review will focus on arthropod transmission to humans with respect to vector species, modes of transmission, geographic differences and F. tularensis subspecies and clades

Remobilization of Tol2 transposons in Xenopus tropicalis

<p>Abstract</p> <p>Background</p> <p>The Class II DNA transposons are mobile genetic elements that move DNA sequence from one position in the genome to another. We have previously demonstrated that the naturally occurring <it>Tol2 </it>element from <it>Oryzias latipes </it>efficiently integrates its corresponding non-autonomous transposable element into the genome of the diploid frog, <it>Xenopus tropicalis. Tol2 </it>transposons are stable in the frog genome and are transmitted to the offspring at the expected Mendelian frequency.</p> <p>Results</p> <p>To test whether <it>Tol2 </it>transposons integrated in the <it>Xenopus tropicalis </it>genome are substrates for remobilization, we injected <it>in vitro </it>transcribed <it>Tol2 </it>mRNA into one-cell embryos harbouring a single copy of a <it>Tol2 </it>transposon. Integration site analysis of injected embryos from two founder lines showed at least one somatic remobilization event per embryo. We also demonstrate that the remobilized transposons are transmitted through the germline and re-integration can result in the generation of novel GFP expression patterns in the developing tadpole. Although the parental line contained a single <it>Tol2 </it>transposon, the resulting remobilized tadpoles frequently inherit multiple copies of the transposon. This is likely to be due to the <it>Tol2 </it>transposase acting in discrete blastomeres of the developing injected embryo during the cell cycle after DNA synthesis but prior to mitosis.</p> <p>Conclusions</p> <p>In this study, we demonstrate that single copy <it>Tol2 </it>transposons integrated into the <it>Xenopus tropicalis </it>genome are effective substrates for excision and random re-integration and that the remobilized transposons are transmitted through the germline. This is an important step in the development of 'transposon hopping' strategies for insertional mutagenesis, gene trap and enhancer trap screens in this highly tractable developmental model organism.</p

Remobilization of Sleeping Beauty transposons in the germline of Xenopus tropicalis

<p>Abstract</p> <p>Background</p> <p>The <it>Sleeping Beauty </it>(<it>SB</it>) transposon system has been used for germline transgenesis of the diploid frog, <it>Xenopus tropicalis</it>. Injecting one-cell embryos with plasmid DNA harboring an <it>SB </it>transposon substrate together with mRNA encoding the <it>SB </it>transposase enzyme resulted in non-canonical integration of small-order concatemers of the transposon. Here, we demonstrate that <it>SB </it>transposons stably integrated into the frog genome are effective substrates for remobilization.</p> <p>Results</p> <p>Transgenic frogs that express the <it>SB</it>10 transposase were bred with <it>SB </it>transposon-harboring animals to yield double-transgenic 'hopper' frogs. Remobilization events were observed in the progeny of the hopper frogs and were verified by Southern blot analysis and cloning of the novel integrations sites. Unlike the co-injection method used to generate founder lines, transgenic remobilization resulted in canonical transposition of the <it>SB </it>transposons. The remobilized <it>SB </it>transposons frequently integrated near the site of the donor locus; approximately 80% re-integrated with 3 Mb of the donor locus, a phenomenon known as 'local hopping'.</p> <p>Conclusions</p> <p>In this study, we demonstrate that <it>SB </it>transposons integrated into the <it>X. tropicalis </it>genome are effective substrates for excision and re-integration, and that the remobilized transposons are transmitted through the germline. This is an important step in the development of large-scale transposon-mediated gene- and enhancer-trap strategies in this highly tractable developmental model system.</p

A new strategy for waterborne disease prevention

In many parts of the developing world, drinking water is collected from unsafe sources and is further contaminated during storage in household vessels. We have developed a simple, inexpensive system for point-of-use disinfection and storage of water which has 3 elements: for disinfection, a sodium hypochlorite solution produced from water and salt using appropriate technology; for safe storage, a 20-litre plastic vessel with a narrow mouth, lid, and spigot (referred to hereafter as the special vessel); and community education to ensure proper use of this system and to teach populations about the association between contaminated water and disease (Mintz, 1995). A field test of this system in El Alto, Bolivia, demonstrated a high level of acceptance among impoverished Aymara Indian families (Quick, 1996). Stored water in households that used the system had lower levels of contamination with E. coli than water in households that used their traditional storage systems. A second field test among vendors in the markets of Guatemala City, Guatemala, showed that there were lower levels of contamination with fecal coliform bacteria in samples of stored water and beverages from vendors using this system than from vendors not using this system (Sobel, 1997). Two field trials have been conducted in the past 3 years to test the effectiveness of this system in preventing diarrhea and its sustainability on a large scale

Identifying factors associated with sedentary time after stroke. Secondary analysis of pooled data from nine primary studies.

<p><b>Background</b>: High levels of sedentary time increases the risk of cardiovascular disease, including recurrent stroke.</p> <p><b>Objective</b>: This study aimed to identify factors associated with high sedentary time in community-dwelling people with stroke.</p> <p><b>Methods</b>: For this data pooling study, authors of published and ongoing trials that collected sedentary time data, using the activPAL monitor, in community-dwelling people with stroke were invited to contribute their raw data. The data was reprocessed, algorithms were created to identify sleep-wake time and determine the percentage of waking hours spent sedentary. We explored demographic and stroke-related factors associated with total sedentary time and time in uninterrupted sedentary bouts using unique, both univariable and multivariable, regression analyses.</p> <p><b>Results</b>: The 274 included participants were from Australia, Canada, and the United Kingdom, and spent, on average, 69% (SD 12.4) of their waking hours sedentary. Of the demographic and stroke-related factors, slower walking speeds were significantly and independently associated with a higher percentage of waking hours spent sedentary (p = 0.001) and uninterrupted sedentary bouts of <i>>30</i> and <i>>60 min</i> (p = 0.001 and p = 0.004, respectively). Regression models explained 11–19% of the variance in total sedentary time and time in prolonged sedentary bouts.</p> <p><b>Conclusion</b>: We found that variability in sedentary time of people with stroke was largely unaccounted for by demographic and stroke-related variables. Behavioral and environmental factors are likely to play an important role in sedentary behavior after stroke. Further work is required to develop and test effective interventions to address sedentary behavior after stroke.</p

Landscape and Residential Variables Associated with Plague-Endemic Villages in the West Nile Region of Uganda

Plague, caused by the bacteria Yersinia pestis , is a severe, often fatal disease. This study focuses on the plagueendemic West Nile region of Uganda, where limited information is available regarding environmental and behavioral risk factors associated with plague infection. We conducted observational surveys of 10 randomly selected huts within historically classified case and control villages (four each) two times during the dry season of 2006 ( N = 78 case huts and N = 80 control huts), which immediately preceded a large plague outbreak. By coupling a previously published landscape-level statistical model of plague risk with this observational survey, we were able to identify potential residence-based risk factors for plague associated with huts within historic case or control villages (e.g., distance to neighboring homestead and presence of pigs near the home) and huts within areas previously predicted as elevated risk or low risk (e.g., corn and other annual crops grown near the home, water storage in the home, and processed commercial foods stored in the home). The identified variables are consistent with current ecologic theories on plague transmission dynamics. This preliminary study serves as a foundation for future case control studies in the area

Interventions to help coral reefs under global change – a complex decision challenge

Climate change is impacting coral reefs now. Recent pan-tropical bleaching events driven by unprecedented global heat waves have shifted the playing field for coral reef management and policy. While best-practice conventional management remains essential, it may no longer be enough to sustain coral reefs under continued climate change. Nor will climate change mitigation be sufficient on its own. Committed warming and projected reef decline means solutions must involve a portfolio of mitigation, best practice conventional management and coordinated restoration and adaptation measures involving new and perhaps radical interventions. We propose that proactive research and development to expand the reef management toolbox fast but safely, combined with expedient trialling of promising interventions is now urgently needed, whatever emissions trajectory the world follows. We discuss the challenges and opportunities of embracing new interventions in a race against time, including their risks and uncertainties. Ultimately, solutions to the climate challenge for coral reefs will require consideration of what society wants, what can be achieved technically and economically, and what opportunities we have for action in a rapidly closing window. Finding solutions that work for coral reefs and people will require exceptional levels of coordination of science, management and policy, and open engagement with society. It will also require compromise, because reefs will change under climate change despiteour best interventions. We argue that being clear about society’s priorities, and understanding both the opportunities and risks that come with an expanded toolset, can help us make the most of a challenging situation

Normal Globular Cluster Systems in Massive Low Surface Brightness Galaxies

We present the results of a study of the globular cluster systems of 6 massive spiral galaxies, originally cataloged as low surface brightness galaxies but here shown to span a wide range of central surface brightness values, including two intermediate to low surface brightness galaxies. We used the Advanced Camera for Surveys on board HST to obtain photometry in the F475W and F775W bands and select sources with photometric and morphological properties consistent with those of globular clusters. A total of 206 candidates were identified in our target galaxies. From a direct comparison with the Galactic globular cluster system we derive specific frequency values for each galaxy that are in the expected range for late-type galaxies. We show that the globular cluster candidates in all galaxies have properties consistent with globular cluster systems of previously studied galaxies in terms of luminosity, sizes and color. We establish the presence of globular clusters in the two intermediate to low surface brightness galaxies in our sample and show that their properties do not have any significant deviation from the behavior observed in the other sample galaxies. Our results are broadly consistent with a scenario in which low surface brightness galaxies follow roughly the same evolutionary history as normal (i.e. high surface) brightness galaxies except at a much lower rate, but require the presence of an initial period of star formation intense enough to allow the formation of massive star clusters.Comment: 14 pages, 6 figures. AJ accepte