title: Loss of maternal Smad5 in zebrafish embryos affects patterning and morphogenesis of optic primordia.
abstract: The mechanisms of patterning and morphogenesis of vertebrate eye primordia are heavily debated. Taking advantage of the maternal effect of a zebrafish smad5 null mutation (Mm169), we investigate the effect of early signaling by members of the bone morphogenetic proteins (Bmps) on eye field patterning and optic vesicle morphogenesis. In contrast to previous Xenopus and chick studies demonstrating a late dorsalizing effect of Bmp4 expressed in the dorsal neural retina itself, we show that patterning of the eye primordia already starts during blastula and early gastrula stages. At these stages, bmps expressed on the ventrolateral side of the embryo promote dorso-distal fates in the entire neuroectoderm, including the eye primordia. Despite a normal split of the eye field in the midline, the eye primordia of Mm169 embryos fail to evaginate laterally. They display a concentric pattern with retinal cells in the center and optic stalk cells in the periphery, representing a flattened version of the topologic relationships present in the mature wild-type eye. Different interpretations of these latter findings are presented. They can be best explained with a model according to which zebrafish eye morphogenesis occurs as a telescopic extension of disc-like, concentric primordia, similar to the development of appendages from imaginal discs in Drosophila.
authors.affiliation: Max-Planck Institute for Immunobiology, Freiburg, Germany. hammerschmid@immunbio.mpg.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Hammerschmidt
authors.forename: Carina
authors.initials: C
authors.lastname: Kramer
authors.forename: Matthias
authors.initials: M
authors.lastname: Nowak
authors.forename: Wiebke
authors.initials: W
authors.lastname: Herzog
authors.forename: Joachim
authors.initials: J
authors.lastname: Wittbrodt
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005123:Eye / Q000033:anatomy & histology / Q000196:embryology*; D005260:Female; D017403:In Situ Hybridization; D008297:Male; D009024:Morphogenesis; D010641:Phenotype; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D051902:Smad5 Protein; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics; D029961:Zebrafish Proteins
chemical_list: D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D010750:Phosphoproteins; D051902:Smad5 Protein; D015534:Trans-Activators; D029961:Zebrafish Proteins; C497801:smad5 protein, zebrafish