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

First meeting of the Portuguese Society for Developmental Biology (SPBD)

[excerpt] The 1st Meeting of the Portuguese Society for DevelopmentalBiology (SPBD – Sociedade Portuguesa de Biologia doDesenvolvimento; was held during two sunny autumndays at the Instituto Gulbenkian de Ciência (IGC) locatedin the beautiful seaside city of Oeiras. This smallmeeting provided unprecedented conditions for Portuguese Developmental Biology researchers to know what is being done inPortugal, to receive feedback on their own work and to establishstrong and productive national collaborations.(undefined

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

The vertebrate Embryo Clock: Common players dancing to a different beat

Vertebrate embryo somitogenesis is the earliest morphological manifestation of the characteristic patterned structure of the adult axial skeleton. Pairs of somites flanking the neural tube are formed periodically during early development, and the molecular mechanisms in temporal control of this early patterning event have been thoroughly studied. The discovery of a molecular Embryo Clock (EC) underlying the periodicity of somite formation shed light on the importance of gene expression dynamics for pattern formation. The EC is now known to be present in all vertebrate organisms studied and this mechanism was also described in limb development and stem cell differentiation. An outstanding question, however, remains unanswered: what sets the different EC paces observed in different organisms and tissues? This review aims to summarize the available knowledge regarding the pace of the EC, its regulation and experimental manipulation and to expose new questions that might help shed light on what is still to unveil.info:eu-repo/semantics/publishedVersio

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

Altered cogs of the clock: Insights into the embryonic etiology of spondylocostal dysostosis

Spondylocostal dysostosis (SCDO) is a rare heritable congenital condition, characterized by multiple severe malformations of the vertebrae and ribs. Great advances were made in the last decades at the clinical level, by identifying the genetic mutations underlying the different forms of the disease. These were matched by extraordinary findings in the Developmental Biology field, which elucidated the cellular and molecular mechanisms involved in embryo body segmentation into the precursors of the axial skeleton. Of particular relevance was the discovery of the somitogenesis molecular clock that controls the progression of somite boundary formation over time. An overview of these concepts is presented, including the evidence obtained from animal models on the embryonic origins of the mutant-dependent disease. Evidence of an environmental contribution to the severity of the disease is discussed. Finally, a brief reference is made to emerging in vitro models of human somitogenesis which are being employed to model the molecular and cellular events occurring in SCDO. These represent great promise for understanding this and other human diseases and for the development of more efficient therapeutic approaches.PTDC/BEX-BID/5410/2014, SFRH/BD/146043/2019, UID/BIM/04773/2019info:eu-repo/semantics/publishedVersio

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

Multiple transcripts regulate glucose-triggered mRNA decay of the lactate transporter JEN1 from Saccharomyces cerevisiae

The Saccharomyces cerevisiae JEN1 gene encoding the lactate transporter undergoes strong catabolic repression at both transcriptional and post-transcriptional levels. JEN1 mRNA decay is greatly accelerated upon the addition of a pulse of glucose, fructose or mannose to induced cell cultures. Mapping of the 5´UTRs and 3´UTRs of JEN1 transcripts revealed multiple transcription start-sites located at position -51, +391 or +972, depending on the cell culture conditions. The presence of the JEN1(+391) transcript correlated with rapid glucose-triggered mRNA degradation of the JEN1(-51) transcript, whereas when the small transcript started at position +972, the JEN1(-51) mRNA turnover rate was unaffected. Overexpressed JEN1(+391) transcript accelerated JEN1(-51) mRNA decay in all conditions tested but was not translated. We propose that the JEN1(+391) transcript may have a ‘‘sensor-like’’ function, regulating glucose-triggered degradation of JEN1(-51) protein-coding mRNA.Fundação para a Ciência e a Tecnologia (FCT) - Programa Operacional "Ciência, Tecnologia, Inovação (POCTI) - POCTI/BIO/38106/2001 (Eixo 2, Medida 2.3, QCAIII-FEDER), BD/15737/98, SFRH/BPD/9432/2002. Deutsche Forschungsgemeinschaft (SFB 579)

THE INFLUENCE OF COLD IN PROPRIOCEPTION OF THE NORMAL KNEE JOINT

The objective of this study was to determine whether the therapeutic use of cold, affects proprioception when applied to the knee joint. Cryotherapy decreases sensory and motor nerve conduction velocities, which are necessary for a normal proprioceptive acuity. Normal proprioceptive acuity is necessary in order to avoid injuries of the musculoskelectal system. Sixty-four healthy volunteers, aged 18-25, moderately active men and women were recruited from a large sample of University students. Subjects were randomly assigned to either the control or the experimental group. The subjects of the experimental group were subjected to 20 min of temperature at constant (5ºC), with an ice application to the knee joint. The results showed that cold does not affect the joint position sense in a normal knee