Linkage of cardiac left-right asymmetry and dorsal-anterior development in Xenopus.
The left-right body axis is defined relative to the dorsal-ventral and anterior-posterior body axes. Since left-right asymmetries are not randomly oriented with respect to dorsal-ventral and anterior-posterior spatial patterns, it is possible that a common mechanism determines all three axes in a coordinate manner. Two approaches were undertaken to determine whether alteration in dorsal-anterior development perturbs the left-right orientation of heart looping. Treatments known to decrease dorsal-anterior development in Xenopus laevis, UV irradiation during the first cell cycle or Xwnt-8 DNA injections into dorsal blastomeres, caused an increase in cardiac left-right reversals. The frequency of left-right reversal was correlated with the severity of dorsal-anterior perturbation and with the extent of anterior notochord regression. Injection of Xwnt-8 DNA into dorsal midline cells resulted in decreased dorsal-anterior development and a correlated increase in cardiac left-right reversals. In contrast, injection of Xwnt-8 DNA into cardiac progenitor blastomeres did not result in left-right reversals, and dorsal-anterior development and notochord formation were normal. Disrupting development of dorsal-anterior cells, including cells that give rise to the Organizer region and the notochord, results in the randomization of cardiac left-right asymmetry. These results suggest dorsal-anterior development and the regulation of left-right orientation are linked.
Danos
M C
MC
Department of Cell Biology and Neuroanatomy, University of Minnesota, Minneapolis 55455, USA.
Yost
H J
HJ
D000818:Animals; D015870:Gene Expression; D006321:Heart / Q000196:embryology*; D017403:In Situ Hybridization; D009024:Morphogenesis; D009672:Notochord / Q000502:physiology; D010641:Phenotype; D014466:Ultraviolet Rays; D014982:Xenopus laevis / Q000196:embryology*