Molecular cloning, genetic mapping, and developmental expression of bovinePOU5F1

We describe isolation and characterization of the bovine ortholog of POU5F1 (bPOU5F1) encoding octamer-binding transcription factor-4 (Oct-4). The org anization of bPOU5F1 is similar to its human and murine orthologs, and it s hares 90.6% and 81.7% overall identity at the protein level, respectively. Transient transfection of luciferase reporter constructs in murine P19 embr yonal carcinoma cells demonstrated that bPOU5F1 has a functional promoter a nd contains two enhancer elements, of which one is repressed by retinoic ac id. bPOU5F1 was mapped to the major histocompatibility complex on chromosom e 23. bPOU5F1 mRNA was detected by nested reverse transcription-polymerase chain reaction in immature oocytes and in in vitro-produced preattachment-s tage embryos. Oct-4 in oocytes and in vitro-produced preattachment-stage em bryos was demonstrated by indirect immunofluorescence. Confocal laser scann ing microscopy revealed Oct-4 in both the inner cell mass and trophoblast c ells of the blastocyst until Day 10 of development. Immunofluorescence perf ormed on the outgrowths formed at Day 13 postfertilization from in vitro-pr oduced Day 8 blastocysts showed Oct-4 staining in all cells. This expressio n pattern suggests that bPOU5F1 acts early in bovine embryonic development but that its expression is not restricted to pluripotent cells of the blast ocyst.