EXPRESSION OF 2 ZEBRAFISH HOMOLOGS OF THE MURINE SIX3 GENE DEMARCATESTHE INITIAL EYE PRIMORDIA

The murine homeobox gene Six3 and its Drosophila homologue sine oculis both have regulatory functions in eye development. We report the isol ation and characterization of two zebrafish genes, six3 and six6, that are closely related to the murine Six3 gene. Zebrafish six3 may be th e structural orthologue, while the six6 gene is more similar with resp ect to embryonic expression. Transcripts of both zebrafish sir genes a re first detected in involuting axial mesendoderm and, subsequently, i n the overlying anterior neural plate from which the optic vesicles an d the forebrain will develop. Direct correspondence between six3/six6 expression boundaries and the optic vesicles indicate essential roles in defining the eye primordia. During later stages only the six6 gene displays similar features of expression in the eyes and rostral brain as reported previously for murine Six3. (C) 1998 Elsevier Science Irel and Ltd.