Cell Movements at Hensen’s Node Establish Left/Right Asymmetric Gene Expression in the Chick

Abstract

Migration and Asymmetry Although vertebrates show asymmetry in internal body organization, the earliest steps toward establishing different anatomies on the left and right sides are not conserved. How this is achieved in birds has been especially confusing. Gros et al. (p. 941 , published online 9 April) show that in chicks some of the earliest left-right asymmetric domains of gene expression, including those of Sonic hedgehog (Shh) and Fibroblast growth factor 8 (Fgf8) , are produced passively. Genes are activated in bilateral cell populations, followed by rearrangements that shuffle Shh -expressing cells.