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Projeto de investigação
Centre for Biomedical Research
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Novel dynamics and functions of Fibronectin in early vertebrate development
Publication . Gomes De Almeida, Patrícia; Thorsteinsdóttir, Sólveig; Palmeirim, Isabel; Andrade, Raquel P.
The metameric body plan of vertebrates is established during somitogenesis, one of the most complex morphogenetic events during development. Somites epithelialize periodically from the anterior-most presomitic mesoderm, and this rhythmicity is thought to be controlled by cyclic traveling waves of gene expression that sweep the tissue anteriorly. Although the spatial and temporal regulation of somitogenesis has been extensively studied, how the periodicity of genetic oscillations is translated into periodic somite epithelialization remains elusive. Furthermore, while knockout experiments have implicated the extracellular matrix component fibronectin in somite formation, much of the roles of its qualitative features deriving from its assembly state are still unknown.
The aim of this thesis is to re-address the role of fibronectin during paraxial mesoderm development, particularly during somite morphogenesis. In Chapter 2, we describe fibronectin production and assembly dynamics during early embryogenesis and found that it is highly dynamic throughout paraxial mesoderm development, as different forms of fibronectin assembly (autocrine vs paracrine) correlate with exquisite morphogenetic events. In Chapter 3 we re-address the role of fibronectin during somite formation in vivo. We show that an intact fibronectin matrix and downstream mechanotransduction signaling are required for correct segmentation clock dynamics and somite morphogenesis. Our results suggest that the fibronectin matrix and its downstream chemical and mechanical cues couple genetic oscillations with timely somite morphogenesis. In Chapter 4 we investigate the role of fibronectin in somite maturation. We demonstrate that normal fibronectin assembly is required for correct Sonic hedgehog signaling in the somite, which in turn controls fibronectin production in this tissue, suggesting that fibronectin and Sonic cooperate to orchestrate somite patterning and differentiation.
This thesis demonstrates that fibronectin is a dynamic pivotal player regulating paraxial mesoderm development. It also highlights the previously unappreciated importance of the extracellular matrix and its derived mechanical cues during embryonic development.
O contributo da nomeação rápida automatizada na predição do desempenho na leitura e na sua perturbação
Publication . Araújo, Susana; Reis, Alexandra; Faísca, Luís; Moura, Octávio; Pereira, Marcelino; Simões, Mário
Early Brain Sensitivity to Word Frequency and Lexicality During Reading Aloud and Implicit Reading
Publication . Faísca, Luís; Reis, Alexandra; Araújo, Susana
The present study investigated the influence of lexical word properties on the early stages
of visual word processing (<250 ms) and how the dynamics of lexical access interact with
task-driven top-down processes. We compared the brain’s electrical response
(event-related potentials, ERPs) of 39 proficient adult readers for the effects of word
frequency and word lexicality during an explicit reading task versus a visual immediaterepetition detection task where no linguistic intention is required. In general, we observed
that left-lateralized processes linked to perceptual expertise for reading are task
independent. Moreover, there was no hint of a word frequency effect in early ERPs, while
there was a lexicality effect which was modulated by task demands: during implicit reading,
we observed larger N1 negativity in the ERP to real words compared to pseudowords,
but in contrast, this modulation by stimulus type was absent for the explicit reading aloud
task (where words yielded the same activation as pseudowords). Thus, data indicate that
the brain’s response to lexical properties of a word is open to influences from top-down
processes according to the representations that are relevant for the task, and this occurs
from the earliest stages of visual recognition (within ~200 ms). We conjectured that the
loci of these early top-down influences identified for implicit reading are probably restricted
to lower levels of processing (such as whole word orthography) rather than the process
of lexical access itself.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UID/BIM/04773/2013