NPR-A regulates self-renewal and pluripotency of embryonic stem cells

Self-renewal and pluripotency of embryonic stem (ES) cells are maintained by several signaling cascades and by expression of intrinsic factors, such as Oct4, Nanog and Sox2. The mechanism regulating these signaling cascades in ES cells is of great interest. Recently, we have demonstrated that natriuretic peptide receptor A (NPR-A), a specific receptor for atrial and brain natriuretic peptides (ANP and BNP, respectively), is expressed in pre-implantation embryos and in ES cells. Here, we examined whether NPR-A is involved in the maintenance of ES cell pluripotency. RNA interference-mediated knockdown of NPR-A resulted in phenotypic changes, indicative of differentiation, downregulation of pluripotency factors (such as Oct4, Nanog and Sox2) and upregulation of differentiation genes. NPR-A knockdown also resulted in a marked downregulation of phosphorylated Akt. Furthermore, NPR-A knockdown induced accumulation of ES cells in the G1 phase of the cell cycle. Interestingly, we found that ANP was expressed in self-renewing ES cells, whereas its level was reduced after ES cell differentiation. Treatment of ES cells with ANP upregulated the expression of Oct4, Nanog and phosphorylated Akt, and this upregulation depended on NPR-A signaling, because it was completely reversed by pretreatment with either an NPR-A antagonist or a cGMP-dependent protein kinase inhibitor. These findings provide a novel role for NPR-A in the maintenance of self-renewal and pluripotency of ES cells.     

Inactivation of Klf5 by zinc finger nuclease downregulates expression of pluripotent genes and attenuates colony formation in embryonic stem cells

Recent studies suggest that Klf5 is required to maintain embryonic stem (ES) cells in an undifferentiated state. However, whether Klf5 can be inactivated by novel fusion technology of zinc finger nucleases (ZFN) has never before been examined. Therefore, we used ZFN technology to target the Klf5 gene in mouse ES cells, and examined the effects of the Klf5 gene on the expression of pluripotency-related genes, Oct3/4, Nanog, and Sox2 and on the self-renewal of ES cells. In Klf5–ZFN-transfected cells, expression of the Klf5 mRNA was downregulated by ~80 % compared to the control. Furthermore, expression of the Oct3/4 and Nanog mRNAs was significantly decreased in the Klf5–ZFN-targeted cells. RT-PCR analysis, however, showed no significant change in the level of Sox2 mRNA, but a decreased trend was evident in the Klf5–ZFN-targeted cells. Moreover, we observed the spontaneous differentiation of Klf5–ZFN-transfected cells and quantitative analysis revealed a significant decrease in colony formation in Klf5–ZFN-transfected cells. In conclusion, our data suggest that ZFN methodology is an effective approach to target the Klf5 gene and that Klf5 plays an important role in the maintenance of ES cell self-renewal.