Regulation of vertebrate left–right asymmetries by extracellular matrix

Abstract

THE vertebrate body is organized along three geometric axes: anterior–posterior, dorsal–ventral and left–right. Left–right axis formation, displayed in heart and gut development, is the least understood, even though it has been studied for many years^1–4. In Xenopus laevis gastrulae, a fibronectin-rich extracellular matrix is deposited on the basal surface of ectoderm cells^5,6 over which cardiac and visceral primordia move during development. Here I report experiments in which localized perturbation of a small patch of extracellular matrix by microsurgery was correlated with localized randomization of left–right asymmetries. Global perturbation of the extracellular matrix by microinjection of Arg-Gly-Asp peptides or heparinase into the blastocoel resulted in global randomization of left-right asymmetries. From these observations, I suggest that left–right axial information is contained in the extracellular matrix early in development and is independently transmitted to cardiac and visceral primordia.