B-box and SPRY domain containing protein (BSPRY) is associated with the maintenance of mouse embryonic stem cell pluripotency and early embryonic development.

Mouse embryonic stem (ES) cells consist of heterogeneous populations with differing abilities to proliferate and differentiate. We previously demonstrated that the expression level of platelet endothelial cell adhesion molecule 1 (PECAM1)/CD31 was positively correlated with the undifferentiated state of mouse ES cells. In order to screen for a novel gene(s) involved in ES cell pluripotency, we performed an oligo microarray analysis and identified that B-box and SPRY domain containing protein (BSPRY) was expressed at high levels in PECAM1-positive cells. Two splice isoforms of BSPRY, BSPRY-1 and BSPRY-2, were expressed in undifferentiated ES cells and in blastocysts. Knockdown of BSPRY-1/2 in ES cells significantly reduced the number of undifferentiated colonies and caused increased expression of primitive ectoderm marker gene Fgf5. The overexpression of BSPRY-2 reciprocally increased the number of undifferentiated ES cells in the presence of LIF. Similarly, injection of BSPRY-1/2 siRNAs into 2-cell embryos caused developmental retardation and degeneration of embryos, and a significant decrease in the number of cells, especially in the inner cell mass (ICM), was observed at the blastocyst stage. Furthermore, microinjection of a BSPRY-1 expression vector into pronuclear stage embryos resulted in an increase in the hatching blastocysts rate after 120 h of culture. These results suggest that BSPRY-1 and BSPRY-2 are associated with both ES cell pluripotency and early embryonic development.