Cloning, characterization and expression of zvep, a novel vitelline envelope‐specific gene in the zebrafish ovary

Abstract

The egg envelope is a specialized extracellular matrix that surrounds and protects the oocyte and plays significant roles in animal reproductive and developmental processes. Using the NCBI digital differential display program we identified an EST sequence (XM_001340234.1) acquired from zebrafish ovary cDNA libraries in GeneBank. The full-length cDNA of this transcript was obtained by 3'and 5' RACE and further confirmed by PCR and sequencing. The full-length cDNA of the novel gene is 2,720 bp and encodes a protein of 761 amino acids. RT-PCR and Western blot analysis showed its expression in ovary and brain but not in other tissues. In situ hybridization demonstrates that the mRNA is transcribed in ooplasm of stage I, II, and III oocytes. Interestingly, immunohistochemistry on zebrafish ovarian sections showed that protein expression in the vitelline envelope was located to two thin positive lines in the stage III oocytes. These ovarian expression patterns show that this is a new component of the vitelline envelope that is synthesized during early developing oocytes. This protein was named ZVEP (zebrafish vitelline envelope protein) and it did not have any homology with other known vitelline envelope genes. Thus, we found that zvep is a novel gene related to the vitelline envelope in zebrafish.