p73 is one of the p53 family members which are transcription factors involved in the regulation of cell proliferation, apoptosis, and differentiation. In this study, we cloned the p73 cDNA from zebrafish ovary RNA. The consensus open reading frame (1923 bp) encodes a polypeptide of 640 amino acids which shares 70-95% identity to the p73 of other vertebrates. Expression of zebrafish p73 mRNA is restricted to tissues such as skin, fin, brain, ovary, and testis, in contrast to the ubiquitous expression of zebrafish p53 and p63. During embryonic development, p73 transcripts are detected from the zygote period to the early larva stage. Whole-mount in situ hybridization reveals that p73 expression is in the brain, including olfactory bulbs, telencephalon, and hypothalamus, as well as in the pharyngeal arches and the nose. Moreover, p73 protein is found in the ovary and testis sections by immunohistochemical staining. (C) 2003 Elsevier Inc. All rights reserved.