Segmentally iterated expression of an engrailed-class gene in the embryo of an australian onychophoran

Abstract

 We have identified an engrailed-class (en-class) gene and determined the distribution pattern of its protein during embryogenesis in a member of the Onychophora. The results of this work add to our understanding of the evolution of development and in addition, they contribute information toward clarifying the phylogenetic position of this group. We observe transient expression in a portion of each developing segment. By the time limbs have formed, segmental expression of en-class protein is restricted to the mesoderm. This pattern shares important spatio-temporal characteristics with those of Annelida and Arthropoda, both of which have members that express en-class genes segmentally in mesoderm and ectoderm.