Joint interpretation of AER/FGF and ZPA/SHH over time and space underlies hairy2 expression in the chick limb

Embryo development requires precise orchestration of cell proliferation and differentiation in both time and space. A molecular clock operating through gene expression oscillations was first described in the presomitic mesoderm (PSM) underlying periodic somite formation. Cycles of HES gene expression have been further identified in other progenitor cells, including the chick distal limb mesenchyme, embryonic neural progenitors and both mesenchymal and embryonic stem cells. In the limb, hairy2 is expressed in the distal mesenchyme, adjacent to the FGF source (AER) and along the ZPA-derived SHH gradient, the two major regulators of limb development. Here we report that hairy2 expression depends on joint AER/FGF and ZPA/SHH signaling. FGF plays an instructive role on hairy2, mediated by Erk and Akt pathway activation, while SHH acts by creating a permissive state defined by Gli3-A/Gli3-R>1. Moreover, we show that AER/FGF and ZPA/SHH present distinct temporal and spatial signaling properties in the distal limb mesenchyme: SHH acts at a long-term, long-range on hairy2, while FGF has a shortterm, short-range action. Our work establishes limb hairy2 expression as an output of integrated FGF and SHH signaling in time and space, providing novel clues for understanding the regulatory mechanisms underlying HES oscillations in multiple systems, including embryonic stem cell pluripotency. (C) 2012. Published by The Company of Biologists Ltd.FCT, Portugal [SFRH/BD/33176/2007]; Ciencia2007 Program Contract (Portuguese Government); IBB/CBME, LA; FCT, Portugal (National and FEDER COMPETE Program funds) [PTDC/SAU-OBD/099758/2008, PTDC/SAU-OBD/105111/2008]info:eu-repo/semantics/publishedVersio

Limb patterning: from signaling gradients to molecular oscillations

The developing forelimb is patterned along the proximal-distal and anterior-posterior axes by opposing gradients of retinoic acid and fibroblast growth factors and by graded sonic hedgehog signaling, respectively. However, how coordinated patterning along both axes is accomplished with temporal precision remains unknown. The limb molecular oscillator hairy2 was recently shown to be a direct readout of the combined signaling activities of retinoic acid, fibroblast growth factor and sonic hedgehog in the limb mesenchyme. Herein, an integrated time-space model is presented to conciliate the progress zone and two-signal models for limb patterning. We propose that the limb clock may allow temporal information to be decoded into positional information when the distance between opposing signaling gradients is no longer sufficient to provide distinct cell fate specification.C.J.S. was supported by Fundacao para a Ciencia e a Tecnologia, Portugal (grant SFRH/BPD/89493/2012); R.P.A. is funded by Ciencia 2007 Program Contract (Portuguese Government) and Programa Operacional Regional do Norte (ON.2) NORTE-07-0124-FEDER-000017. This work was supported by research grants from Institute for Biotechnology and Bioengineering/Centro de Biomedicina Molecular e Estrutural, LA (to I.P.), by the national Portuguese funding through Fundacao para a Ciencia e a Tecnologia (National and FEDER COMPETE Program funds: PTDC/SAU-OBD/099758/2008 and PTDC/SAU-BID/121459/2010 to I.P. and R.P.A., respectively) and by PEst-OE/EQB/LA0023/2011

Chick Hairy1 protein interacts with Sap18, a component of the Sin3/HDAC transcriptional repressor complex

<p>Abstract</p> <p>Background</p> <p>The vertebrate adult axial skeleton, trunk and limb skeletal muscles and dermis of the back all arise from early embryonic structures called somites. Somites are symmetrically positioned flanking the embryo axial structures (neural tube and notochord) and are periodically formed in a anterior-posterior direction from the presomitic mesoderm. The time required to form a somite pair is constant and species-specific. This extraordinary periodicity is proposed to depend on an underlying somitogenesis molecular clock, firstly evidenced by the cyclic expression of the chick <it>hairy1 </it>gene in the unsegmented presomitic mesoderm with a 90 min periodicity, corresponding to the time required to form a somite pair in the chick embryo. The number of <it>hairy1 </it>oscillations at any given moment is proposed to provide the cell with both temporal and positional information along the embryo's anterior-posterior axis. Nevertheless, how this is accomplished and what biological processes are involved is still unknown. Aiming at understanding the molecular events triggered by the somitogenesis clock Hairy1 protein, we have employed the yeast two-hybrid system to identify Hairy1 interaction partners.</p> <p>Results</p> <p>Sap18, an adaptor molecule of the Sin3/HDAC transcriptional repressor complex, was found to interact with the C-terminal portion of the Hairy1 protein in a yeast two-hybrid assay and the Hairy1/Sap18 interaction was independently confirmed by co-immunoprecipitation experiments. We have characterized the expression patterns of both <it>sap18 </it>and <it>sin3a </it>genes during chick embryo development, using <it>in situ </it>hybridization experiments. We found that both <it>sap18 </it>and s<it>in3a </it>expression patterns co-localize <it>in vivo </it>with <it>hairy1 </it>expression domains in chick rostral presomitic mesoderm and caudal region of somites.</p> <p>Conclusion</p> <p>Hairy1 belongs to the hairy-enhancer-of-split family of transcriptional repressor proteins. Our results indicate that during chick somitogenesis Hairy1 may mediate gene transcriptional repression by recruiting the Sin3/HDAC complex, through a direct interaction with the Sap18 adaptor molecule. Moreover, since <it>sap18 </it>and <it>sin3a </it>are not expressed in the PSM territory where <it>hairy1 </it>presents cyclic expression, our study strongly points to different roles for Hairy1 throughout the PSM and in the prospective somite and caudal region of already formed somites.</p

Comprehensive analysis of fibroblast growth factor receptor expression patterns during chick forelimb development

Specific interactions between fibroblast growth factors (Fgf1-22) and their tyrosine kinase receptors (FgfR1-4) activate different signalling pathways that are responsible for the biological processes in which Fgf signalling is implicated during embryonic development. In the chick, several Fgf ligands (Fgf2, 4,8, 9, 10, 12, 13 and 18) and the four FgfRs (FgfR 1, 2, 3 and 4) have been reported to be expressed in the developing limb. The precise spatial and temporal expression of these transcripts is important to guide the limb bud to develop into a wing/leg. In this paper, we present a detailed and systematic analysis of the expression patterns of FgfR1, 2, 3 and 4 throughout chick wing development, by in situ hybridisation on whole mounts and sections. Moreover, we characterize for the first time the different isoforms of FGFR1-3 by analysing their differential expression in limb ectoderm and mesodermal tissues, using RT-PCR and in situ hybridisation on sections. Finally, isoform-specific sequences for FgfR1IIIb, FgfR1IIIc, FgfR3IIIb and FgfR3IIIc were determined and deposited in GenBank with the following accession numbers: GU053725, GU065444, GU053726, GU065445, respectively.Fundacao para a Ciencia e Tecnologia [SFRH/BD/33176/2007]; Portuguese Government; Fundacao para a Ciencia e Tecnologia, Portugal [OBD/099758/2008]; EU; IBB/CBM

Efficacy, safety and acceptability of a new chewable formulationversusthe solid tablet of mebendazole against hookworm infections in children: an open-label, randomized controlled trial

Background; : Soil-transmitted helminths (STHs) infect almost 1·5 billion people worldwide. The control of STH infections is based on preventive chemotherapy using either albendazole or mebendazole. Before being widely used, a sufficient body of evidence on efficacy, safety and acceptability is warranted for the new chewable child-friendly formulation of mebendazole that was recently developed.; Methods; : We conducted a randomised controlled superiority trial in four primary schools and kindergartens on Pemba Island, Tanzania. We considered eligible children aged 3 to 12 years with a hookworm infection intensity of at least 50 eggs per gram (EPG) of stool and no chronic diseases. Participants were allocated to treatment arms (ratio 1:1) using a computer generated random sequence. Our primary outcome was geometric mean based egg reduction rate (ERR) against hookworm assessed 14-21 days post-treatment. This trial complete and is registered with ClinicalTrials.gov, number NCT03995680 (June 24, 2019).; Findings; : 397 children were eligible and randomised into the solid (198) or chewable (199) tablet arms, of whom 393 were analysed. We found no significant difference between both formulations in terms of ERR (solid 70·8% versus chewable 68·5%, difference in ERRgeometric mean 2·3%-points, 95% CI -7·8 to 12·6, p = 0.65) and CR (11·2 versus 12·7%, 95% CI -4·9 to 7·9, p = 0.65) against hookworm infections. Adverse events were mild in both treatment arms.; Interpretations; : Though we could not demonstrate superiority in terms of efficacy of the new formulation, the difference between arms was small and therefore, the chewable formulation could be safely used as an alternative to swallowable tablets, in particular in young children who may have swallowing difficulties. This might help increase compliance and, consequently, enhance the effect of preventive chemotherapy

Current Knowledge and Conservation of the Wild Mammals of the Gulf of Guinea Oceanic Islands

Oceanic islands are usually difficult for mammals to colonize; consequently, the native mammal fauna is typically species-poor, often consisting of just a few species of bats. The oceanic islands of the Gulf of Guinea are no exception to this pattern. Still, the known mammal richness is relatively high for the small size of the islands. Out of a total of 13 native species, including 11 bats and 2 shrews, at least 7 species and 3 subspecies are single-island endemics. In addition to native species, at least 6 other wild mammals have been introduced to the islands purposely or accidentally by humans. Some of these are among the world’s most notorious invasive species and cause damage to native species, ecosystems, and humans. Predation by exotic species can threaten native island mammals, which are especially sensitive due to their small populations and limited ranges. These impacts are likely worsened by other threats, such as forest degradation and climate change, and a general lack of knowledge about the natural history of most species also hampers the implementation of conservation measures. Therefore, fostering further research on the endemic-rich mammal fauna of these islands is vital to ensure their persistence.info:eu-repo/semantics/publishedVersio

Malnutrition, anemia, micronutrient deficiency and parasitic infections among schoolchildren in rural Tanzania

BACKGROUND: Malnutrition, anemia, micronutrient deficiency and parasitic infections continue to impact the nutritional status and health of children in lower-income countries, however not enough data concerning this issue is available. The aim of this study was to assess the distribution of nutritional indicators, anemia and micronutrient deficiency and their underlying risk factors among schoolchildren in south-eastern Tanzania. METHOD/PRINCIPAL FINDINGS: This cross-sectional study enrolled primary schoolchildren aged 6-12 years from Kikwawila and Kiberege wards, Tanzania. In total 471 schoolchildren underwent physical examination and provided blood, stool and urine samples for micronutrient level assessment, nutritional and anemia status, and parasitic infection status. We employed bivariate and multivariate logistic regression to determine the association between nutritional statuses, anemia, micronutrient deficiency and parasitic infections. We found that 23.90%, 12.60% and 16.20% of schoolchildren were stunted, underweight and wasted, respectively. About 14% of schoolchildren were found to be anemic and were more likely to be diagnosed with Plasmodium falciparum infection (aOR: 3.95, 95% CI: 2.73-5.67). Vitamin A (34.70%) and vitamin B12 (8.80%) were the most prevalent micronutrients found to be deficient in diagnosed children. Finally, we found that schoolchildren attending the most rural schools were five times more likely to be diagnosed with at least one micronutrient deficiency (aOR: 5.04, 95% CI: 2.38-11.44). CONCLUSIONS/SIGNIFICANCE: Malnutrition, anemia and micronutrient deficiency still pose a significant health burden among schoolchildren living in rural Tanzania. To effectively tackle this burden, health interventions such as deworming, micronutrient supplementation, vector control, health education and access to clean water and improved sanitation should be strengthened and made sustainable

Informed consent procedure in a double blind randomized anthelminthic trial on Pemba Island, Tanzania: do pamphlet and information session increase caregivers knowledge?

Background In clinical research, obtaining informed consent from participants is an ethical and legal requirement. Conveying the information concerning the study can be done using multiple methods yet this step commonly relies exclusively on the informed consent form alone. While this is legal, it does not ensure the participant’s true comprehension. New effective methods of conveying consent information should be tested. In this study we compared the effect of different methods on the knowledge of caregivers of participants of a clinical trial on Pemba Island, Tanzania. Methods A total of 254 caregivers were assigned to receive (i) a pamphlet (n = 63), (ii) an oral information session (n = 62) or (iii) a pamphlet and an oral information session (n = 64) about the clinical trial procedures, their rights, benefits and potential risks. Their post-intervention knowledge was assessed using a questionnaire. One group of caregivers had not received any information when they were interviewed (n = 65). Results In contrast to the pamphlet, attending an information session significantly increased caregivers’ knowledge for some of the questions. Most of these questions were either related to the parasite (hookworm) or to the trial design (study procedures). Conclusions In conclusion, within our trial on Pemba Island, a pamphlet was found to not be a good form of conveying clinical trial information while an oral information session improved knowledge. Not all caregivers attending an information session responded correctly to all questions; therefore, better forms of communicating information need to be found to achieve a truly informed consent

Efficacy and safety of a single dose versus a multiple dose regimen of mebendazole against hookworm infections in children : a randomised, double-blind trial

Background: Single-dose mebendazole is widely used in preventive chemotherapy against the soil-transmitted helminths (STHs) Ascaris lumbricoides, hookworm and Trichuris trichiura, yet it shows limited efficacy against hookworm and T. trichiura infections. The use of adapted treatment regimens might provide a strategy to control and eliminate STH infections in STH-persistent settings. We evaluated the safety and efficacy of the multiple dose mebendazole regimen (3 days 100 mg bid) versus a single dose of 500 mg mebendazole in a setting with high STH prevalence and high drug pressure. Methods: This randomised, double-blind clinical trial took place in a primary school on Pemba Island, Tanzania, in school-aged children (6–12 years). Using a computer random number generator (block size 10), hookworm-positive children were randomly assigned (1:1) to either a single or multiple dose regimen of mebendazole by an independent statistician. Two stool samples were collected at baseline and follow-up (18 to 22 days after treatment) for Kato-Katz analysis. The primary outcome was cure rate (CR) against hookworm. Secondary outcomes were egg reduction rate (ERR) against hookworm, CRs and ERRs against A. lumbricoides and T. trichiura, and tolerability assessed 3, 24 and 48 h post-treatment. Participants, investigators, caregivers, outcome assessors and the trial statistician were blinded. This trial is registered with ClinicalTrials.gov, number NCT03245398. Findings: 93 children were assigned to each treatment arm. 185 children completed treatment and provided follow-up stool samples. CR against hookworm was significantly higher in the multiple dose (98%) than in the single dose arm (13%, OR 389.1, 95% CI 95.2 to 2885.7%, p < 0.001). 34 and 42 children reported mild adverse events in the single and multiple dose arms, respectively. The most common events were abdominal pain, headache and diarrhoea. Interpretation: The poor performance of single dose mebendazole against hookworm infections was confirmed, but the multiple dose treatment regimen of mebendazole showed high efficacy. Hence, multiple dose mebendazole might provide a treatment strategy in given epidemiological situations to boost control and elimination of STH infections. Funding: PATH

Secondary forest regeneration benefits old-growth specialist bats in a fragmented tropical landscape

Tropical forest loss and fragmentation are due to increase in coming decades. Understanding how matrix dynamics, especially secondary forest regrowth, can lessen fragmentation impacts is key to understanding species persistence in modified landscapes. Here, we use a whole-ecosystem fragmentation experiment to investigate how bat assemblages are influenced by the regeneration of the secondary forest matrix. We surveyed bats in continuous forest, forest fragments and secondary forest matrix habitats, similar to 15 and similar to 30 years after forest clearance, to investigate temporal changes in the occupancy and abundance of old-growth specialist and habitat generalist species. The regeneration of the second growth matrix had overall positive effects on the occupancy and abundance of specialists across all sampled habitats. Conversely, effects on generalist species were negligible for forest fragments and negative for secondary forest. Our results show that the conservation potential of secondary forests for reverting faunal declines in fragmented tropical landscapes increases with secondary forest age and that old-growth specialists, which are often of most conservation concern, are the greatest beneficiaries of secondary forest maturation. Our findings emphasize that the transposition of patterns of biodiversity persistence in island ecosystems to fragmented terrestrial settings can be hampered by the dynamic nature of human-dominated landscapes.Peer reviewe