Protein tyrosine phosphatase 1B (PTP1B) is required for cardiac lineage differentiation of mouse embryonic stem cells

Protein tyrosine phosphatase 1B (PTP1B) has been shown to regulate multiple cellular events such as differentiation, cell growth, and proliferation; however, the role of PTP1B in differentiation of embryonic stem (ES) cells into cardiomyocytes remains unexplored. In the present study, we investigated the effects of PTP1B inhibition on differentiation of ES cells into cardiomyocytes. PTP1B mRNA and protein levels were increased during the differentiation of ES cells into cardiomyocytes. Accordingly, a stable ES cell line expressing PTP1B shRNA was established. In vitro, the number and size of spontaneously beating embryoid bodies were significantly decreased in PTP1B-knockdown cells, compared with the control cells. Decreased expression of cardiac-specific markers Nkx2-5, MHC-α, cTnT, and CX43, as assessed by real-time PCR analysis, was further confirmed by immunocytochemistry of the markers. The results also showed that PTP1B inhibition induced apoptosis in both differentiated and undifferentiated ES cells, as presented by increasing the level of cleaved caspase-3, cytochrome C, and cleaved PARP. Further analyses revealed that PTP1B inhibition did not change proliferation and pluripotency of undifferentiated ES cells. Taken together, the data presented here suggest that PTP1B is essential for proper differentiation of ES cells into cardiomyocytes.