Identification of a homologue of POU5F1 (OCT3/4) in a marsupial, the brushtail possum

Several morphological features of early development differ between marsupia ls and eutherians. These include early overt conceptus polarity, the mode o f segregation of pluriblast and trophoblast lineages, and the superficial p osition of the pluriblast within the unilaminar blastocyst epithelium. Know ledge of the molecular mechanisms of early development is lacking in marsup ials. We have cloned from the brushtail possum, Trichosurus vulpecula, the partial cDNA of a marsupial homologue of mammalian POU5F1, which encodes oc tamer-binding transcription factor-4 (Oct-4). The 579 bp cloned coding sequ ence of possum PDU5F1 (tvPOU5F1) shaves 74, 78, and 79% identify with murin e Pou5f1, human POU5F1, and bovine bPOU5F1, respectively, at the protein le vel. The mRNA for tvPOU5F1 was detected by in situ hybridization in oogonia and in oocytes of growing follicles, but not in early meiotic oocytes. In a gastrulation-stage conceptus, high tvPOU5F1 expression was found in the e mbryonic ectoderm, with low or undetectable expression in other cell types. These results are comparable with those of murine and bovine expression st udies, and suggest that the putative role of POU5F1 in totipotent and pluri potent cells is conserved among mammals. (C) 2001 Wiley-Liss, Inc.