Pou5f1 protein expression and posttranslational modification during early zebrafish development.

Background: Pou5f1/Oct4 is a transcription factor essential for maintenance of pluripotency in mammals and for control of blastula and gastrula stage gene regulatory networks in zebrafish. Information on Pou5f1 protein distribution was before this study not available for zebrafish. Therefore, we generated polyclonal antibodies that selectively recognize Pou5f1 and analyzed its protein distribution and modification during development.

Results: Pou5f1 protein is present in unfertilized oocytes, and persists in all embryonic and enveloping layer cell nuclei until the end of gastrulation, but is absent from yolk syncytial nuclei. Pou5f1 is subject to multiple developmentally regulated phosphorylations, with the higher phosphorylated forms prevailing in the oocyte and during late gastrulation.

Conclusions: The developmental protein profile correlates with the stages during which deep cells are not committed to a specific germ layer. The posttranslational modification by phosphorylation opens the possibility that Pou5f1 may be subject to temporal or region specific modulation of its activity or stability by embryonic signaling mechanisms.