Identification and expression analysis of two zebrafish E2F5 genes during oogenesis and development.

During the process of screening genes that are preferentially expressed in zebrafish germ cells, we isolated an E2F family member zE2F5b, which is a truncated isoform of zebrafish E2F5a. The E2F transcription factors are thought to play an essential role in cell cycle progression. Reverse transcription polymerase chain reaction and whole mount in situ hybridization analyses have demonstrated that both zE2F5a and zE2F5b mRNAs are predominantly expressed in stage I and II oocytes. In early development, the two zE2F5 transcripts are expressed by many parts of the embryo and are then restricted to the brain area. Interestingly, zE2F5b mRNA is detected later in the lens and optic tectum while zE2F5a mRNA is absent. Our data suggests that E2F5 may play important roles in zebrafish brain, eye and ovarian development.