Restricted expression of the homeobox gene prox 1 in developing zebrafish.

Prox 1 is a vertebrate homeobox gene which is homologous to the Drosophila transcription factor, prospero. We have isolated a prox 1 cDNA from zebrafish, which encodes a protein that has 82%, 84% and 83% amino acid identity with chicken, mouse and human Prox 1, respectively. Antibodies raised against human Prox 1 cross-react with zebrafish Prox 1 and are used here to determine the expression patterns of Prox 1 during zebrafish embryogenesis by whole-mount immunohistochemistry. In the 10-somite embryo, Prox 1 is expressed over the prospective lens placode and over a broad region of epithelium extending from the eye to the otic vesicle. As embryogenesis proceeds, Prox 1 expression in the eye lens becomes intense, and is detected in maturing muscle pioneer cells and superficial muscle cells. In the CNS, Prox 1 is expressed in a stripe along the forebrain-midbrain boundary, in a segmented pattern in the ventral hindbrain, and in selected cells of the ventral spinal cord. Additional sites of Prox 1 expression include the lateral line primordium, the trigeminal ganglia, the otic vesicle and occasional endodermal cells.