Entire mesodermal mantle behaves as Spemann's organizer in dorsoanterior enhanced Xenopus laevis embryos

Journal Article · Sun May 01 00:00:00 EDT 1988 · Dev. Biol.; (United States)

DOI:https://doi.org/10.1016/0012-1606(88)90189-3· OSTI ID:6968591

Kao, K R; Elinson, R P

The body plan of Xenopus laevis can be respecified by briefly exposing early cleavage stage embryos to lithium. Such embryos develop exaggerated dorsoanterior structures such as a radial eye and cement gland. In this paper, we demonstrate that the enhanced dorsoanterior phenotype results from an overcommitment of mesoderm to dorsoanterior mesoderm. Histological and immunohistochemical observations reveal that the embryos have a greatly enlarged notochord with very little muscle tissue. In addition, they develop a radial, beating heart, suggesting that lithium also specifies anterior mesoderm and pharyngeal endoderm. Randomly oriented diametrically opposed marginal zone grafts from lithium-treated embryos, when transplanted into ultraviolet (uv)-irradiated axis-deficient hosts, rescue dorsal axial structures. These transplantation experiments demonstrate that the entire marginal zone of the early gastrula consists of presumptive dorsal mesoderm. Vital dye marking experiments also indicate that the entire marginal zone maps to the prominent proboscis that is composed of chordamesoderm and represents the long axis of the embryo. These results suggest that lithium respecifies the mesoderm of Xenopus laevis embryos so that it differentiates into the Spemann organizer. We suggest that the origin of the dorsoanterior enhanced phenotypes generated by lithium and the dorsoanterior deficient phenotypes generated by uv irradiation are due to relative quantities of organizer. Our evidence demonstrates the existence of a continuum of body plan phenotypes based on this premise.

• Research Organization: Univ. of Toronto, Ontario (Canada)
• OSTI ID: 6968591
• Journal Information: Dev. Biol.; (United States), Vol. 127:1
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
EMBRYOS
CELL DIFFERENTIATION
LITHIUM
GENETIC EFFECTS
HEART
PHENOTYPE
TRANSPLANTS
ULTRAVIOLET RADIATION
ALKALI METALS
BIOLOGICAL EFFECTS
BODY
CARDIOVASCULAR SYSTEM
ELECTROMAGNETIC RADIATION
ELEMENTS
METALS
ORGANS
RADIATIONS
560300* - Chemicals Metabolism & Toxicology
560152 - Radiation Effects on Animals- Animals