Developmental expression of class III and IV POU domain genes in the zebrafish

Using redundant primers in a PCR based cloning strategy, POU-domain encoding sequences representing two different class III genes (brain-1.1, brain-1.2) and one class IV gene (brain-3.1) were identified in zebrafish. Using the PCR clones to screen a zebrafish gastrula cDNA library, a third class III POU gene was identified (brain-1.0). RT-PCR assays performed with gene-specific primers indicated that the four POU genes exhibited distinct patterns of expression in developing embryos and adult fish. Like their mammalian homologs, the class III genes were expressed early in development and in the adult brain, while the class IV gene was poorly expressed during early development but highly expressed in the adult eye. Since two of the POU PCR clones were obtained from genomic DNA, the fish genes may also be similar to their mammalian homologs in being largely devoid of introns.