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

Epidemiology of pediatric schistosomiasis in hard-to-reach areas and populations: a scoping review protocol

Background: Schistosomiasis is a neglected tropical disease (NTD) that affects millions of people. Children are the most vulnerable group to developing overt disease. An estimated 779 million people are at risk of schistosomiasis and 50 million preschool-age children (PSAC) need treatment. PSAC are not currently targeted by national chemotherapy campaigns due to a lack of suitable pediatric formulations of praziquantel. The Pediatric Praziquantel Consortium has developed an orally dispersible praziquantel formulation (arpraziquantel) and is facilitating its adoption for schistosomiasis control by endemic countries through the ADOPT program - an implementation research program that paves the way for the large-scale delivery of the child-friendly formulation to treat schistosomiasis in preschool-aged children in endemic countries. A key challenge for comprehensive NTD control including schistosomiasis is reaching all at-risk populations, including those hard to reach. Main access barriers include geographic, social and economic conditions. Objective : This scoping literature review aims to document the epidemiology of schistosomiasis in children under 6 years of age living in hard-to-reach areas and populations. Methods : This review will adopt the five-stage scoping review process of identifying the research question, identifying relevant studies, study selection, charting data and collating, summarizing and reporting results. Electronic databases including Medline, Web of Science, Embase (Ovid), LILACS and African Journals OnLine (AJOL) will be searched for relevant articles. Two independent reviewers will screen identified articles using a two-stage approach of reviewing the title/abstract and then the full text of provisionally retained articles. Relevant literatures will be downloaded into EndNote X9 to maintain and manage citation and facilitate the overall review process. A meta-analysis will be conducted if indicated. Relevance : The results will provide insights into the burden of schistosomiasis among marginalized PSAC, aiming to produce evidence on the need for inclusion of this population when designing the expansion of preventive chemotherapy programs

Timing embryo segmentation: dynamics and regulatory mechanisms of the vertebrate segmentation clock

All vertebrate species present a segmented body, easily observed in the vertebrate column and its associated components, which provides a high degree of motility to the adult body and efficient protection of the internal organs. The sequential formation of the segmented precursors of the vertebral column during embryonic development, the somites, is governed by an oscillating genetic network, the somitogenesis molecular clock. Herein, we provide an overview of the molecular clock operating during somite formation and its underlying molecular regulatory mechanisms. Human congenital vertebral malformations have been associated with perturbations in these oscillatory mechanisms. Thus, a better comprehension of the molecular mechanisms regulating somite formation is required in order to fully understand the origin of human skeletal malformations.Fundacao paraa Ciencia e a Tecnologia, Portugal [SFRH/BD/27796/2006, SFRH/BPD/80588/2011]; Programa Operacional Regional do Norte (ON.2) [NORTE-07-0124-FEDER-000017]; Centro de Biomedicina Molecular e Estrutural, LA; Fundacao para a Ciencia e a Tecnologia (National and FEDER COMPETE Program funds) [PTDC/SAU-BID/121459/2010, PTDC/SAU-OBD/099758/2008]; [PEst-OE/EQB/LA0023/2011

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

Bird taxonomic and functional responses to land abandonment in wood-pastures

Wood-pastures are socio-ecological systems covering vast areas in Europe. Although used for grazing and production of various forest goods, wood-pastures harbour a rich biodiversity and are usually considered as High Nature Value Farmlands. However, socio-economic pressures are driving the transformation of these valuable landscapes from multi-functional, heterogeneous habitats to homogeneous areas through either intensification or land abandonment. We investigated how changes in management intensity influence the taxonomic diversity, functional diversity and functional composition of birds in these landscapes using generalized linear models. In contrast to taxonomic diversity, functional diversity decreased significantly towards shrub-dominated and less heterogeneous areas related to the abandonment of grazing and/or understory management practices. Grassland and generalist species, and associated guilds such as granivores, ground-nesters and ground-foragers are almost absent less managed areas. On the other hand, shrub-dominated areas favour forest species, particularly understory/canopy foragers and arboreal nesters, although the forest guild is still well-represented in actively managed, heterogeneous areas. Our results indicate the abandonment of wood-pasture management affects the prevalence of grassland and generalist species, leading to functional diversity loss and potentially reduced ecosystem functioning. We suggest non-intensive, active management is needed to maintain habitat heterogeneity and canopy openness, enhancing trait diversity in wood-pastures.Peer reviewe

The impact of alternative science education methodologies on the motivation and acquisition of scientific concepts

Fully aware of the increasing importance of active and experimental learning, this study has been conducted in Portugal between 2007 and 2008 and was the first of this kind to ever be conducted in this country. Thirty eight students of the school E.B. 2, 3 D. Maria II (middle school) participated in the extra-curricular activity entitled “Scientists for a Day”, previous developed by the Life and Health Science Research Institute/School of Health Science (ICVS/ECS), University of Minho. This activity realized in the School E.B. 2, 3 D. Maria II and organized by teachers of the same School consisted in a set of laboratory activities subdivided into four experimental stations, namely: 1st Station – “Extracting banana DNA”; 2nd Station – “Acid/Base”, 3rd Station – “Observation of chicken embryos” and 4th Station – “Five Senses”. The general objectives of this activity were to stimulate the pleasure of knowledge, encourage critical views, heighten the interest in science, motivate students towards experimental work and demystify the idea of what a Scientist is. In an effort to validate this activity and evaluate what they have learned, the students were asked to answer a questionnaire before and immediately after this activity. In this study we observed a clear correlation between the use of active and experimental learning activities, and an increase in scientific knowledge

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

Unifying low and high mass star formation through density amplified hubs of filaments

Context: Star formation takes place in giant molecular clouds, resulting in mass-segregated young stellar clusters composed of Sun-like stars, brown dwarves, and massive O-type(50-100\msun) stars. Aims: To identify candidate hub-filament systems (HFS) in the Milky-Way and examine their role in the formation of the highest mass stars and star clusters. Methods: Filaments around ~35000 HiGAL clumps that are detected using the DisPerSE algorithm. Hub is defined as a junction of three or more filaments. Column density maps were masked by the filament skeletons and averaged for HFS and non-HFS samples to compute the radial profile along the filaments into the clumps. Results: ~3700~(11\%) are candidate HFS of which, ~2150~(60\%) are pre-stellar, ~1400~(40\%) are proto-stellar. All clumps with L>10^4 Lsun and L>10^5 Lsun at distances respectively within 2kpc and 5kpc are located in the hubs of HFS. The column-densities of hubs are found to be enhanced by a factor of ~2 (pre-stellar sources) up to ~10 (proto-stellar sources). Conclusions: All high-mass stars preferentially form in the density enhanced hubs of HFS. This amplification can drive the observed longitudinal flows along filaments providing further mass accretion. Radiation pressure and feedback can escape into the inter-filamentary voids. We propose a "filaments to clusters" unified paradigm for star formation, with the following salient features: a) low-intermediate mass stars form in the filaments slowly (10^6yr) and massive stars quickly (10^5yr) in the hub, b) the initial mass function is the sum of stars continuously created in the HFS with all massive stars formed in the hub, c) Feedback dissiption and mass segregation arise naturally due to HFS properties, and c) explain age spreads within bound clusters and formation of isolated OB associations.Comment: 20 pages, 17 figures, Accepted by Astronomy and Astrophysic

Star formation and ionized regions in the Inner Galactic Plane

We present a comprehensive statistical study to understand the impact of galactic bubble structures detected in the Spitzer observations throughout the galactic plane on the star formation process. We analysed 1 360 galactic bubbles and ∼70 000 star-forming sources, from both Hi-GAL and GLIMPSE surveys, located in their vicinity. The spatial distribution of the star-forming sources seen in surface density maps reveal a clear evolutionary gradient, were more evolved Young Stellar Objects (YSOs) are typically found in the center, while recent star-forming sources (prestellar and protostellar) can be seen at the edges of the bubbles. Based on the dynamic ages derived for the bubbles and numerical simulations we find that the timescale for star-formation are better describe advocating for the pre-existence of density structures in the medium prior to the creation of the ionizing source(s). Identical pattern of age distribution of star-forming sources has been found in a recent detailed study of the nearby λ Ori bubble using APOGEE-2 and GAIA DR2 observations, which provides compelling evidence of what we obtained in our statistical result. In light of these results we propose a scenario for the star formation process in expanding ionizing bubbles