Expression of AmKrox, a starfish ortholog of a sea urchin transcription factor essential for endomesodermal specification.

The sea urchin zinc finger transcription factor SpKrox is a regulatory gene that functions early in endomesodermal specification. We report here the cloning and expression of an ortholog of this gene, AmKrox, from the starfish Asterina miniata. The echinoderm Krox proteins belong to a class of transcription factors that includes the vertebrate Blimp-1 proteins and two putative insect proteins. AmKrox is expressed in a ring around the vegetal pole of the blastula. During gastrulation, expression is detected surrounding the blastopore and in the posterior archenteron. In the early bipinnaria larva transcripts are detected in the midgut and hindgut. Despite differences in early development of sea urchins and starfish, the expression of these Krox transcription factors is highly conserved.