Antagonistic signaling by Caronte, a novel Cerberus-related gene, establishes left-right asymmetric gene expression.

Left-right asymmetry is initiated during chick embryogenesis in small domains near Hensen's node. Subsequently, broad asymmetric gene expression domains are established in the lateral plate mesoderm, ultimately determining the directionality of morphogenetic events. The transfer of asymmetric information from the node to the lateral plate is mediated by Caronte (Car), a novel member of the Cerberus/Dan gene family, which induces targets by antagonizing symmetrically expressed BMP signals. In addition, BMP antagonism by Car induces asymmetric expression of Lefty in the midline, preventing spread of left-sided signals to the contralateral side.