TRANSIENT EXPRESSION OF A NOVEL SIX3-RELATED ZEBRAFISH GENE DURING GASTRULATION AND EYE FORMATION

Both the Drosophila homeobox gene sine oculis and its murine homologue Six3 have regulatory functions in eye development. In zebrafish, in a ddition to two previously reported homologues of murine Six3?, we have identified a related gene (six7). Although the deduced Six7 protein s hares less than 68% sequence identity with the other known zebrafish S ix3-like proteins, the embryonic expression patterns have highly conse rved features. The six7 transcripts are first detected in involuting a xial mesendoderm and, subsequently, in the overlying neurectoderm from which the forebrain and optic primordia develop. Similar to the two o ther zebrafish Six3 homologues, the expression boundaries of six7 corr espond quite closely with the edges of the optic vesicles. Hence, the partially overlapping expression domains of these three six genes prob ably contribute to anteroposterior specification and in defining the e ye primordia. (C) 1998 Elsevier Science B.V. All rights reserved.