Abstract
Purpose: :
bcl6
Methods: :
Morpholino knock-down was performed in zebrafish embryos, and in situ hybridization, immunohistochemistry, and histological methods were utilized to determine the effects on eye development.
Results: :
Loss of Bcl6 function leads to colobomas and ventral retina defects. bcl6 knockdown also results in up-regulation of p53, a previously known Bcl6 target, and an increase in the number of apoptotic cells in the retina. Knockdown of both bcl6 and p53 prevents colobomas supporting a model in which Bcl6 dependent p53 inhibition in the retina is required for cell survival therein. Loss of Vax1 and Vax2 in zebrafish leads to colobomas (Take-uchi et al., 2003), and we tested whether Vax1 and Vax2 act upstream of bcl6. Indeed, loss of Vax1 and Vax2 resulted in a loss of bcl6 expression, concomitant with induction of p53, and an increase in the number of apoptotic cells in the eye. Interestingly, triple knockdown of vax1, vax2 and p53 rescued colobomas in vax1/vax2 morphants suggesting that Vax1 and Vax2 act upstream of bcl6 to regulate cell survival in the retina. Finally, we identified functional interactions between Bcl6, Bcor and Rybpa during eye development.
Conclusions: :
Bcl6 plays a critical role in preventing apoptosis in the retina during eye development, and this is required to contain the retina and RPE within the optic cup. Vax1 and Vax2 act upstream of bcl6 in the ventral retina, and Bcl6 functions along with Bcor and Rybpa to mediate cell survival by regulating p53 within the developing zebrafish retina.
Keywords: retinal development • gene/expression • transcription factors