title: The midline (notochord and notoplate) patterns the cell motility underlying convergence and extension of the Xenopus neural plate.
abstract: We investigated the role of the dorsal midline structures, the notochord and notoplate, in patterning the cell motilities that underlie convergent extension of the Xenopus neural plate. In explants of deep neural plate with underlying dorsal mesoderm, lateral neural plate cells show a monopolar, medially directed protrusive activity. In contrast, neural plate explants lacking the underlying dorsal mesoderm show a bipolar, mediolaterally directed protrusive activity. Here, we report that "midlineless" explants consisting of the deep neural plate and underlying somitic mesoderm, but lacking a midline, show bipolar, mediolaterally oriented protrusive activity. Adding an ectopic midline to the lateral edge of these explants restores the monopolar protrusive activity over the entire extent of the midlineless explant. Monopolarized cells near the ectopic midline orient toward it, whereas those located near the original, removed midline orient toward this midline. This behavior can be explained by two signals emanating from the midline. We postulate that one signal polarizes neural plate deep cells and is labile and short-lived and that the second signal orients any polarized cells toward the midline and is persistent.
authors.affiliation: Department of Biology, University of Virginia, Charlottesville, VA 22903, USA. mae4z@hotmail.com
authors.forename: Akouavi M
authors.initials: AM
authors.lastname: Ezin
authors.forename: Paul
authors.initials: P
authors.lastname: Skoglund
authors.forename: Ray
authors.initials: R
authors.lastname: Keller
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning; D002465:Cell Movement; D016764:Cell Polarity; D002490:Central Nervous System / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D005456:Fluorescent Dyes; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D018715:Microscopy, Video; D009672:Notochord / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D015398:Signal Transduction; D000071250:Snail Family Transcription Factors; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics; D014404:Tubulin / Q000235:genetics; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics
chemical_list: D005456:Fluorescent Dyes; D053823:Hedgehog Proteins; D000071250:Snail Family Transcription Factors; D015534:Trans-Activators; D014157:Transcription Factors; D014404:Tubulin