Matrix Gla Protein expression pattern in the early avian embryo.

MGP (Matrix Gla Protein) is an extracellular matrix vitamin K dependent protein previously identified as a physiological inhibitor of calcification and shown to be well conserved among vertebrates during evolution. MGP is involved in other mechanisms such as TGF-ß and BMP activity, and a proposed modulator of cell-matrix interactions. MGP is expressed early in vertebrate development although its role has not been clarified. Previous work in the chicken embryo found MGP localization predominantly in the aorta and aortic valve base, but no data is available earlier in development. Here we examined MGP expression pattern using whole-mount in situ hybridization and histological sectioning during the initial stages of chick development. MGP was first detected at HH10 in the head and in the forming dorsal aorta. At the moment of the onset of blood circulation, MGP was expressed additionally in the venous plexus which will remodel into the vitelline arteries. By E2.25, it is clear that the vitelline arteries are MGP positive. MGP expression progresses centrifugally throughout the area vasculosa of the yolk sac. Between stages HH17 and HH19 MGP is seen in the dorsal aorta, heart, notochord, nephric duct, roof plate, vitelline arteries and in the yolk sac, beneath main arterial branches and in the vicinity of several vessels and venules. MGP expression persists in these areas at least until E4.5. These data suggest that MGP expression could be associated with cell migration and differentiation and to the onset of angiogenesis in the developing chick embryo. This data has biomedical relevance by pointing to the potential use of chick embryo explants to study molecules involved in artery calcification.

Expression and function of Ccbe1 in the chick early cardiogenic regions are required for correct heart development.

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.

Expression pattern of zcchc24 during early Xenopus development.

We report the expression pattern of a novel Xenopus laevis gene, zcchc24, which encodes a protein containing two zinc finger domains from the zf-CCHC and zf-3CxxC superfamilies. This protein shares >84% amino acid identity with its vertebrate homologues. During X. laevis embryonic development, zcchc24 is expressed at gastrula stages in the dorsal mesoderm, including the cardiac precursors region. During neurula stages, zcchc24 is expressed as two stripes in the dorsal region, more precisely, in the somitogenic mesoderm until the cardiac mesoderm. At early tailbud stages, zcchc24 continues to be expressed in these regions, but starts to be expressed in the migrating neural crest. Later, this gene is expressed in the head, branchial arches, heart and somites. The zinc finger domains present in Zcchc24 protein and its dynamic gene expression pattern suggest that Zcchc24 might be involved in the regulation of heart, somites and of branchial arch formation/patterning, namely in the regulation of apoptosis.

Identification of differentially expressed genes in the heart precursor cells of the chick embryo.

Genetic evidence has implicated several genes as being critical for heart development. However, the inducers of these genes as well as their targets and pathways they are involved with, remain largely unknown. Previous studies in the avian embryo showed that at HH4 Cerberus (cCer) transcripts are detected in the anterior endomesoderm including the heart precursor cells and later in the left lateral plate mesoderm. We have identified a promoter element of chick cCer able to drive EGFP expression in a population of cells that consistently exit from the anterior primitive streak region, from as early as stage HH3+, and that later will populate the heart. Using this promoter element as a tool allowed us to identify novel genes previously not known to potentially play a role in heart development. In order to identify and study genes expressed and involved in the correct development and differentiation of the vertebrate heart precursor cell (HPC) lineages, a differential screening using Affymetrix GeneChip system technologies was performed. Remarkably, this screening led to the identification of more than 700 transcripts differentially expressed in the heart forming regions (HFR). Bioinformatic tools allowed us to filter the large amount of data generated from this approach and to select a few transcripts for in vivo validation. Whole-mount in situ hybridization and sectioning of selected genes showed heart and vascular expression patterns for these transcripts during early chick development. We have developed an effective strategy to specifically identify genes that are differentially expressed in the HPC lineages. Within this set we have identified several genes that are expressed in the heart, blood and vascular lineages, which are likely to play a role in their development. These genes are potential candidates for future functional studies on early embryonic patterning.

Síndrome da cimitarra: aspectos da endoscopia respiratória / Scimitar syndrome: endoscopic respiratory aspects

Apresenta-se o caso de uma paciente de 10 anos de idade, sexo feminino, assintomática, encaminhada ao serviço com diagnóstico de dextrocardia. A investigaçäo observou-se o sinal radiológico da cimitarra. A broncoscopia e a broncografia evidenciaram ausência de lobos superior e médio e anormalidades na segmentaçäo brônquica do lobo inferior direito. O cateterismo confirmou a drenagem anômala da veia pulmonar direita para a veia cava inferior, configurando a síndrome da cimitarra