Characterization and expression pattern of pouII1, a novel class IIPOU gene in zebrafish

POU domain transcription factors that share a conserved DNA-binding domain, POU domain, are important regulators for the development of embryos in var ious animal species. A novel zebrafish POU domain gene, pouII1 has been clo ned. The pouII1 cDNA is 2080 kb in length and encodes a putative polypeptid e of 596 amino acids. It is placed into class II POU family since it shares a high degree of homology with the known members of this family. Northern hybridization identifies a major transcript of approximately 2.1 kb that wa s present in embryos at the single-cell stage throughout 24 h postfertiliza tion. The whole mount in situ hybridization shows that pouII1 transcripts a re present in the single-cell embryos, strongly suggesting that these trans cripts are of maternal origin. During early development of the embryos, pou II1 mRNA was ubiquitously distributed in all cells and tissues. The transcr ipts are gradually limited to brains and become completely undetectable by day 3. To our knowledge, pouII1 is the first class II POU gene identified i n zebrafish.