Bone marrow stromal cell antigen 2 is broadly expressed in the different pluripotent states of human pluripotent stem cells and regulates the expression of pluripotency genes and three germ layer markers.

Human pluripotent stem cells (hPSCs) have at least three distinct states: naïve pluripotency that represents the cellular states of the pre-implantation epiblast cells, primed pluripotency that represents the cellular states of the post-implantation epiblast cells, and formative pluripotency that represents a developmental continuum between naïve and primed pluripotency. Various cell surface markers have been used to define and analyze primed and naïve hPSCs within heterogeneous populations. However, not much is known about common cell surface markers for the different pluripotent states of hPSCs. To study surface molecules important for maintaining naive pluripotency, in this study, we generated murine monoclonal antibodies (MAbs) specific to naïve hPSCs. Subsequent studies showed that N15-F8, one of the MAbs, bound to both naïve and primed hPSCs. Cell surface biotin labeling and subsequent immunoprecipitation proved that N15-F8 recognized bone marrow stromal antigen 2 (BST2) in a conformation-dependent manner. Quantitative polymerase chain reaction (qPCR) revealed that BST2 expression was decreased during the early stages of differentiation via embryoid body (EB) formation in primed hPSCs. BST2 knockdown in primed hPSCs resulted in reduced expression of pluripotency genes. BST2 knockdown in naïve hPSCs also resulted in reduced expression of pluripotency genes and several naïve and primed pluripotent state-specific genes. BST2 knockdown induced the expression of ectoderm and endoderm markers in primed hPSCs, whereas it suppressed the expression of mesoderm markers. The results suggest that BST2 is broadly expressed in the different pluripotent states of hPSCs and regulates the expression of pluripotency genes and three germ layer markers.