OCT4 and downstream factors are expressed in human somatic urogenital epithelia and in culture of epididymal spheres

The transcription factor OCT4 plays a crucial role in the earliest differentiation of the mammalian embryo and in self-renewal of embryonic stem cells. However, it remains controversial whether this gene is also expressed in somatic tissues. Here, we use a combination of RT-PCR on whole and microdissected tissues, in situ hybridization, immunohistochemistry and western blotting to show that OCT4 and SOX2 together with downstream targets, UTF1 and REX1/ZFP42, are expressed in the human male urogenital tract. We further support these results by the analysis of DNA methylation of a region in the OCT4 promoter. In culture, human primary epididymal cells formed spheres that continued to express the investigated genes for at least 20 days. Transcriptomic analysis of cultured cells showed up-regulation of CD29, CD44 and CD133 that are normally associated with sphere-forming cancer stem cells. Furthermore, stimulation with retinoic acid resulted in down-regulation of OCT4 expression, however, without multilineage differentiation. Our results show that OCT4 and associated genes are expressed in somatic epithelial cells from the urogenital tract and that these cells can form spheres, a general marker of stem cell behaviour.