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Development of the arterial pole of the heart is a critical step in cardiogenesis, yet its embryological origin remains obscure. We have analyzed a transgenic mouse line in which beta-galactosidase activity is observed in the embryonic right ventricle and outflow tract of the heart and in contiguous splanchnic and pharyngeal mesoderm. The nlacZ transgene(More)
During somitogenesis, cells are recruited to the caudal presomitic mesoderm (PSM) from the primitive streak (and later the tail bud), while somites separate from the rostral end as epithelial cubes. This is a regular process, one somite forming every 2 hours in the mouse, that can be simulated by clock and wavefront models. The chick basic helix-loop-helix(More)
From 1996 to 2000, ZEBET (Centre for Documentation and Evaluation of Alternative Methods to Animal Experiments at the BgVV, Berlin, Germany) coordinated the European Centre for the Validation of Alternative Methods (ECVAM) prevalidation and validation study on three embryotoxicity tests: a) a test employing embryonic stem cell lines (EST); b) the micromass(More)
Inactivation of the left-right asymmetry gene Pitx2 has been shown, in mice, to result in right isomerism with associated defects that are similar to that found in humans. We show that the Pitx2c isoform is expressed asymmetrically in a presumptive secondary heart field within the branchial arch and splanchnic mesoderm that contributes to the aortic sac and(More)
Chronic venous disease and venous hypertension are common consequences of valve insufficiency, yet the molecular mechanisms regulating the formation and maintenance of venous valves have not been studied. Here, we provide what we believe to be the first description of venous valve morphogenesis and identify signaling pathways required for the process. The(More)
The pulmonary vein is sleeved by myocardium, which is a major source of atrial fibrillation and is involved in congenital sinus venosus defects. Little is known about the cellular origin and mechanism of formation of the pulmonary myocardium. We observed a biphasic process of pulmonary myocardium formation in mice. Firstly, a myocardial cell population(More)
The sinoatrial node, which resides at the junction of the right atrium and the superior caval vein, contains specialized myocardial cells that initiate the heart beat. Despite this fundamental role in heart function, the embryonic origin and mechanisms of localized formation of the sinoatrial node have not been defined. Here we show that subsequent to the(More)
During gastrulation, the node of the mammalian embryo appears to be an organising centre, homologous to Hensen's node in the chick and the dorsal lip of the amphibian blastopore. In addition, the node serves as a precursor population for the head process, notochord and foregut endoderm. We have studied node architecture and cell morphology by electron(More)
The Wnt genes are known to play fundamental roles during patterning and development of a number of embryonic structures. Receptors for Wnts are members of the Frizzled family of proteins containing a cysteine-rich domain (CRD) that binds the Wnt protein. Recently several secreted frizzled-related proteins (Sfrps) that also contain a CRD have been identified(More)