Evolution and functions of Oct4 homologs in non-mammalian vertebrates

•Evolutionary history of Oct4 homologs Pou5f1 and Pou5f3.•Functional equivalence of Pou5f1 and Pou5f3.•Biological roles of Pou5f1 and Pou5f3 in different vertebrates.

PouV class transcription factor Oct4/Pou5f1 is a central regulator of indefinite pluripotency in mammalian embryonic stem cells (ESCs) but also participates in cell lineage specification in mouse embryos and in differentiating cell cultures. The molecular basis for this versatility, which is shared between Oct4 and its non-mammalian homologs Pou5f1 and Pou5f3, is not yet completely understood. Here, I review the current understanding of the evolution of PouV class transcription factors and discuss equivalent and diverse roles of Oct4 homologs in pluripotency, differentiation, and cell behavior in different vertebrate embryos. This article is part of a Special Issue entitled: The Oct Transcription Factor Family, edited by Dr. Dean Tantin.