Sequence relationships and expression patterns of zebrafish zic2 and zic5 genes.

The zinc finger motif forms a DNA binding domain that is found in a wide variety of proteins. Among them, the members of the zic gene family are highly conserved throughout metazoans. We report here the isolation of two new members of this gene family in zebrafish, zic2.2 and zic5, isolated during random screening for tissue-specific genes. Zic2.2 is closely related to the previously reported zic2 gene, which we propose to rename zic2.1; these two genes form a subfamily with other vertebrate zic2 genes. We compare here the expression patterns of zic2.1, zic2.2, and zic5. All three genes showed dynamic expression patterns starting after the initiation of zygotic transcription, predominantly in the developing neural tube. Compared to zic2.1, zic2.2 was expressed in a similar but distinct manner during early development, particularly in the retina and the forming somites. A zic2.2 ortholog has not been identified in other vertebrate species, suggesting that the zic2.1/zic2.2 pair resulted from a genome duplication event during the evolution of the zebrafish lineage.