--- res: bibo_abstract: - In a large scale screen for mutants with defects in the embryonic development of the zebrafish we identified mutations in four genes, floating head (flh), memo (mom), no tail (ntl), and dec, that are required for early notochord formation. Mutations in flh and ntl have been described previously, while mom and doe are newly identified genes. Mutant mom embryos lack a notochord in the trunk, and trunk somites from the right and left side of the embryo fuse underneath the neural tube. In this respect morn appears similar to flh. In contrast, notochord precursor cells are present in both ntl and doc embryos. In order to gain a greater understanding of the phenotypes, we have analysed the expression of several axial mesoderm markers in mutant embryos of all four genes. In flh and mom, Ntl expression is normal in the germ ring and tailbud, while the expression of Nd and other notochord markers in the axial mesodermal region is disrupted. Nd expression is normal in doc embryos until early semitic stages, when there is a reduction in expression which is first seen in anterior regions of the embryo. This suggests a function for doc in the maintenance of ntl expression. Other notochord markers such as twist, sonic hedgehog and axial are not expressed in the axial mesoderm of ntl embryos, their expression parallels the expression of ntl in the axial mesoderm of mutant doc,flh and mom embryos, indicating that ntl is required for the expression of these markers. The role of doc in the expression of the notochord markers appears indirect via ntl. Floor plate formation is disrupted in most regions in flh and mom mutant embryos but is present in mutant ntl and doc embryos. In mutant embryos with strong ntl alleles the band of cells expressing floor plate markers is broadened. A similar broadening is also observed in the axial mesoderm underlying the floor plate of ntl embryos, suggesting a direct involvement of the notochord precursor cells in floor plate induction. Mutations in al of these four genes result in embryos lacking a horizontal myoseptum and muscle pioneer cells, both of which are thought to be induced by the notochord. These somite defects can be traced back to an impairment of the specification of the adaxial cells during early stages of development. Transplantation of wild-type cells into mutant doc embryos reveals that wild-type notochord cells are sufficient to induce horizontal myoseptum formation in the flanking mutant tissue. Thus dec, like flh and ntl, acts cell autonomously in the notochord. In addition to the four mutants with defects in early notochord formation, we have isolated 84 mutants, defining at least 15 genes, with defects in later stages of notochord development. These are listed in an appendix to this study.@eng bibo_authorlist: - foaf_Person: foaf_givenName: Jörg foaf_name: Odenthal, Jörg foaf_surname: Odenthal - foaf_Person: foaf_givenName: Pascal foaf_name: Haffter, Pascal foaf_surname: Haffter - foaf_Person: foaf_givenName: Elisabeth foaf_name: Vogelsang, Elisabeth foaf_surname: Vogelsang - foaf_Person: foaf_givenName: Michael foaf_name: Brand, Michael foaf_surname: Brand - foaf_Person: foaf_givenName: Fredericus foaf_name: Van Eeden, Fredericus foaf_surname: Van Eeden - foaf_Person: foaf_givenName: Makoto foaf_name: Furutani Seiki, Makoto foaf_surname: Furutani Seiki - foaf_Person: foaf_givenName: Michael foaf_name: Granato, Michael foaf_surname: Granato - foaf_Person: foaf_givenName: Matthias foaf_name: Hammerschmidt, Matthias foaf_surname: Hammerschmidt - foaf_Person: foaf_givenName: Carl-Philipp J foaf_name: Heisenberg, Carl-Philipp J foaf_surname: Heisenberg foaf_workInfoHomepage: http://www.librecat.org/personId=39427864-F248-11E8-B48F-1D18A9856A87 orcid: 0000-0002-0912-4566 - foaf_Person: foaf_givenName: Yunjin foaf_name: Jiang, Yunjin foaf_surname: Jiang - foaf_Person: foaf_givenName: Donald foaf_name: Kane, Donald foaf_surname: Kane - foaf_Person: foaf_givenName: Robert foaf_name: Kelsh, Robert foaf_surname: Kelsh - foaf_Person: foaf_givenName: Mary foaf_name: Mullins, Mary foaf_surname: Mullins - foaf_Person: foaf_givenName: Rachel foaf_name: Warga, Rachel foaf_surname: Warga - foaf_Person: foaf_givenName: Miguel foaf_name: Allende, Miguel foaf_surname: Allende - foaf_Person: foaf_givenName: Eric foaf_name: Weinberg, Eric foaf_surname: Weinberg - foaf_Person: foaf_givenName: Christiane foaf_name: Nüsslein Volhard, Christiane foaf_surname: Nüsslein Volhard bibo_doi: 10.1242/dev.123.1.103 bibo_issue: '1' bibo_volume: 123 dct_date: 1996^xs_gYear dct_isPartOf: - http://id.crossref.org/issn/0950-1991 dct_language: eng dct_publisher: Company of Biologists@ dct_title: Mutations affecting the formation of the notochord in the zebrafish, Danio rerio@ fabio_hasPubmedId: '9007233' ...