title: Development of the left-right axis in amphibians.
abstract: The heart and viscera of vertebrates are formed from primordia that are apparently bilaterally symmetrical. This symmetry is broken during development, yielding organs that develop characteristic asymmetries along the left-right axis. Results from three lines of experimentation on embryos of the amphibian Xenopus laevis indicate that left-right asymmetries are established early in development and that cellular interactions transmit left-right information from one primordium to another. First, a cytoplasmic rearrangement that occurs during the first cell cycle after fertilization may establish left-right asymmetry in some regions of the embryo. Second, a variety of experimental results indicate that embryonic ectoderm or its basal extracellular matrix may transmit left-right axial information to cardiac mesoderm and visceral endoderm. Third, inhibition of proteoglycan synthesis during a narrow period of development, concurrent with the migration of the cardiac primordia to the ventral midline, prevents asymmetrical development of the heart.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley 94720.
authors.forename: H J
authors.initials: HJ
authors.lastname: Yost
mesh_terms: D000663:Amphibians / Q000196:embryology*; D000818:Animals; D002465:Cell Movement; D004707:Endoderm; D005775:Gastrula; D006321:Heart / Q000196:embryology; D008648:Mesoderm; D009024:Morphogenesis; D014466:Ultraviolet Rays / Q000009:adverse effects