REQUIREMENT OF THE MANX GENE FOR EXPRESSION OF CHORDATE FEATURES IN ATAILLESS ASCIDIAN LARVA

An evolutionary change in development was studied in two closely relat ed ascidian species, one exhibiting a conventional tadpole larva and t he other a modified tailless larva. Interspecific hybridization restor es chordate features to the tailless larva. The zinc finger gene Manx is expressed in cells that generate chordate features in the tailed sp ecies but is down-regulated in the tailless species. Manx expression i s restored in hybrid embryos. Antisense oligodeoxynucleotide treatment inhibited Manx expression and chordate features in hybrid embryos, wh ich suggests that Manx is required for development of the chordate lar val phenotype in ascidians.