The development of blood vessels either de novo (vasculogenesis) or from pre-existing vessels (angiogenesis) is a process with relevance to both embryogenesis and medicine. It can be studied particularly well in the zebrafish by taking advantage of its transparency, which allows the use of reporter lines that express Green Fluorescent Protein in endothelial cells, permitting the observation of vessels in the living embryo. The characterization of zebrafish mutants that exhibit a reduced or excessive number of vessels, or vessels with an aberrant morphology, is a key focus of the lab. We are using confocal microscopy, in situ hybridizations and antibody stainings to characterize those mutants, which have all been mapped to narrow regions of the respective chromosomes. Molecular techniques are being used to clone these genes positionally. An additional interest in the lab is osteogenesis. The formation of bone is the net result of the interplay between osteoblasts (cells that build bone) and osteoclasts (cells that remodel bone). In a large scale mutant screen we have identified zebrafish mutants that affect osteoblast function and are studying the process of osteogenesis, using methods very similar to the ones mentioned above. We are particularly interested in mutants that exhibit excessive bone formation, as the functions of the underlying genes are relevant not only to larval development, but possibly also have clinical implications.