PinX1t, a Novel PinX1 Transcript Variant, Positively Regulates Cardiogenesis of Embryonic Stem Cells

Abstract

Background Pin2/ TRF 1‐interacting protein, PinX1, was previously identified as a tumor suppressor. Here, we discovered a novel transcript variant of mP inX1 (mouse PinX1), mP inX1t (mouse PinX1t), in embryonic stem cells ( ESC s). The aims of this investigation were (1) to detect the presence of mP inX1 and mP inX1t in ESC s and their differentiation derivatives; (2) to investigate the role of mP inX1 and mP inX1t on regulating the characteristics of undifferentiated ESC s and the cardiac differentiation of ESC s; (3) to elucidate the molecular mechanisms of how mP inX1 and mP inX1t regulate the cardiac differentiation of ESCs. Methods and Results By 5′ rapid amplification of cDNA ends, 3′ rapid amplification of cDNA ends, and polysome fractionation followed by reverse transcription–polymerase chain reaction, mP inX1t transcript was confirmed to be an intact mRNA that is actively translated. Western blot confirmed the existence of mP inX1t protein. Overexpression or knockdown of mP inX1 (both decreased mP inX1t expression) both decreased while overexpression of mP inX1t increased the cardiac differentiation of ESC s. Although both mP inX1 and mP inX1t proteins were found to bind to cardiac transcription factor mRNA s, only mP inX1t protein but not mP inX1 protein was found to bind to nucleoporin 133 protein, a nuclear pore complex component. In addition, mP inX1t‐containing cells were found to have a higher cytosol‐to‐nucleus ratio of cardiac transcription factor mRNA s when compared with that in the control cells. Our data suggested that mP inX1t may positively regulate cardiac differentiation by enhancing export of cardiac transcription factor mRNA s through interacting with nucleoporin 133. Conclusions We discovered a novel transcript variant of mP inX1, the mP inX1t, which positively regulates the cardiac differentiation of ESC s.