Expression of a zebrafish iroquois homeobox gene, Ziro3, in the midline axial structures and central nervous system.

We describe a zebrafish gene, Ziro3, which is highly homologous to Xenopus and mouse iroquois3. Ziro3 expression starts during gastrulation in the dorsal axial mesoderm that develops into the notochord. Later, the expression is limited to the chordo-neural hinge in the tailbud. Ziro3 expression also occurs in the central nervous system (CNS), excluding the telencephalon. The level of Ziro3 expression differs in odd and even rhombomeres. In the midbrain-hindbrain boundary (MHB) and rhombomere 6, Ziro3 transcripts appear only after the formation of the cerebellum and otic vesicle, respectively.