Article Abstract:
Wnt signals have been shown to be required and sufficient for neural crest cells to adopt pigment cell fates. A zebrafish homolog of microphthalmia-associated transcription factor (MITF) called nacre is needed for differentiation of pigment cells. A promoter region of nacre that has in it Tcf/Lef binding sites, which can mediate Wnt responsiveness were, isolated. The promoter binds to Lef1 protein of zebrafish in vitro. In melanoma cells, a nacre reporter construct is repressed strongly by dominant-negative Tcf. Mutation of Tcf/Lef sites gets rid of Lef1 binding and reporter function in vivo.
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Article Abstract:
A Mix family homeodomain protein that regulates generation of endodermal precursors is encoded by the zebrafish bonnie and clyde (bon) gene. That bon encodes a paired-class homeodomain protein of the Mix family expressed transiently before and during early gastrulation in mesodermal and endodermal progenitors has been shown. Endodermal gene expression and the formation of a gut tube in bon mutants can be rescued by overexpression of bon. It has been shown as well by loss- and gain-of function analyses that Bon functions only downstream of squint and cyclops signaling.
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Article Abstract:
A strategy for the most efficient breeding and screening of proviral insertions has been developed to make a large-scale insertional mutagenesis screening possible. Such a screen is being carried out in zebrafish, in the embryo of which about 2500 genes are essential for normal development. The screen is to isolate about 1000 embryonic mutations. A significant proportion of the mutated genes, those important for normal embryogenesis of a vertebrate, are to be cloned. The first mutants obtained and the rapid cloning of the mutated genes are discussed.
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