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- Generating asymmetries in the early vertebrate embryo: the role of the Cerberus-like familyPublication . Belo, José A.; Silva, Ana C.; Borges, Ana; Filipe, Mário; Bento, Margaret; Gonçalves, Lisa; Vitorino, Marta; Salgueiro, Ana Marisa; Texeira, Vera; Tavares, Ana T.; Marques, SaraOne fundamental aspect of vertebrate embryonic development is the formation of the body plan. For this process, asymmetries have to be generated during early stages of development along the three main body axes: Anterior-Posterior, Dorso-Ventral and Left-Right. We have been studying the role of a novel class of molecules,the Cerberus/Dan gene family. These are dedicated secreted antagonists of three major signaling pathways: Nodal, BMP and Wnt. Our studies contribute to the current view that the fine tuning of signaling is controlled by a set of inhibitory molecules rather than by activators. In this context, the Cerberus-like molecules emerge as key players in the regulation and generation of asymmetries in the early vertebrate embryo.
- Expression and Function of Ccbe1 in the Chick Early Cardiogenic Regions Are Required for Correct Heart DevelopmentPublication . Furtado, João; Bento, Margaret; Correia, Elizabeth; Inacio, Jose Manuel; Belo, José A.During the course of a differential screen to identify transcripts specific for chick heart/hemangioblast precursor cells, we have identified Ccbe1 (Collagen and calcium-binding EGF-like domain 1). While the importance of Ccbe1 for the development of the lymphatic system is now well demonstrated, its role in cardiac formation remained unknown. Here we show by whole-mount in situ hybridization analysis that cCcbe1 mRNA is initially detected in early cardiac progenitors of the two bilateral cardiogenic fields (HH4), and at later stages on the second heart field (HH9-18). Furthermore, cCcbe1 is expressed in multipotent and highly proliferative cardiac progenitors. We characterized the role of cCcbe1 during early cardiogenesis by performing functional studies. Upon morpholino-induced cCcbe1 knockdown, the chick embryos displayed heart malformations, which include aberrant fusion of the heart fields, leading to incomplete terminal differentiation of the cardiomyocytes. cCcbe1 overexpression also resulted in severe heart defects, including cardia bifida. Altogether, our data demonstrate that although cardiac progenitors cells are specified in cCcbe1 morphants, the migration and proliferation of cardiac precursors cells are impaired, suggesting that cCcbe1 is a key gene during early heart development.
- Comparative expression of mouse and chicken shisa homologues during early developmentPublication . Filipe, Mario; Gonçalves Dias da Silva, Lisa; Bento, Margaret; Silva, Ana Cristina; Belo, José A.During vertebrate embryogenesis, fibroblast growth factor (FGF) and Wnt signaling have been implicated in diverse cellular processes, including cell growth, differentiation, and tissue patterning. The recently identified Xenopus Shisa protein promotes head formation by inhibiting Wnt and FGF signaling through its interaction with the immature forms of Frizzled and FGF receptors in the endoplasmic reticulum, which prevents their posttranslational maturation. Here, we describe the mouse and chicken homologues of Xenopus Shisa. The mouse and chicken Shisa proteins share, respectively, 33.6% and 33.8% identity with the Xenopus homolog. In situ hybridization analysis shows that mouse shisa is expressed throughout embryonic development, predominantly in the anterior visceral endoderm, headfolds, somites, forebrain, optic vesicle, and limb buds. Cross-species comparison shows that the expression pattern of cshisa closely mirrors that of mshisa. Our observations indicate that the Shisa family genes are typically expressed in tissues known to require the modulation of Wnt and FGF signaling. Developmental Dynamics 235:2567-2573, 2006. (c) 2006 Wiley-Liss, Inc.
- Functional analysis of novel genes differentially expressed genes in heart/hemangioblast precursor cells (H/HPC)Publication . Belo, José A.; Bento, Margaret C.; Tavares, Ana T.
- Identification of novel genes expressed in the heart/hemangioblast precursor cellsPublication . Bento, Margaret Carvalho; Belo, JoséMany studies using the chick embryo have been performed to identify the heart-forming region of the development embryo. The heart precursor cells (HPC) are generated within bilateral fields in the lateral mesoderm, which consequently converge toward the midline to form a beating linear heart tube. One of the genes expressed by these cells is Caronte (Car). In the avian embryo, Car transcripts are detected in the anterior mesendoderm including the HPC and in the left lateral plate mesoderm. Preliminary results obtained in promoter analysis experiments, showed that a 2.5Kb fragment upstream from the ATG of chick Car was able to drive EGFP expression within the normal Car domains of expression. Furthermore, a large population of EGFP positive cells, corresponding to the heart and the hemangioblast precursor cells (H/HPC) could clearly be visualized exiting the anterior primitive streak region from as early as stage HH3+. In order to identify and study novel genes expressed and involved in the correct development of the vertebrate H/HPC lineages, a differential screening using Affymetrix GeneChip® system technologies was performed. Remarkably, this screening led to the identification of more than 800 new genes potentially expressed in these haematopoesis, angiogenesis or cardiogenesis precursor lineages. Interesting new transcripts were ordered from EST Databases and three newly uncovered genes were studied more thoroughly. Expression pattern through embryonic development was performed by whole mount in situ hybridization, to validate its differential expression characteristic of the H/HPC population. Taken together, the results in this thesis, provides a set of interesting novel candidate genes that may play important roles in the heart development, providing in the longterm useful information with clinical relevance.