An inhibitory effect of Xenopus gastrula ectoderm on muscle cell differentiation and its role for dorsoventral patterning of mesoderm.
In Amphibia, mesoderm cells such as notochord, muscle, and blood are formed as a result of mesoderm induction, the first known inductive interaction during the embryonic development of Vertebrates. Recent evidence shows, however, that, in addition to mesoderm induction, further cell-cell interactions during gastrulation also play an important role in the differentiation of mesoderm cells in Xenopus embryos. Here we report the existence of an inhibitory effect of gastrula ectoderm on muscle cell differentiation. When placed in contact with a muscle progenitor cell population, ectoderm from the ventral side of a gastrula embryo exerts an inhibitory effect on MyoD expression and muscle differentiation. This inhibitory effect is not observed on notochord differentiation. Dorsal ectoderm shows the same extent of inhibitory effect if it is isolated at the early-gastrula stage but gradually loses its effect during gastrulation as it is induced to become neural tissue. Cell mixing experiments have shown that this inhibitory effect, clearly seen in ventral ectoderm, is not observed in ventral mesoderm cells. We propose that the ectoderm emits a signal counteracting dorsalization and the community effect and that this signal plays an important role in the correct dorsoventral patterning of mesoderm.
Kato
K
K
Wellcome CRC Institute, Cambridge, England.
Gurdon
J B
JB
D000818:Animals; D002454:Cell Differentiation; D004475:Ectoderm / Q000502:physiology*; D005260:Female; D005775:Gastrula / Q000502:physiology*; D008648:Mesoderm / Q000502:physiology*; D009132:Muscles / Q000196:embryology*; D017570:MyoD Protein / Q000032:analysis; D014982:Xenopus laevis / Q000196:embryology*
D017570:MyoD Protein