Jingyuan Cao

Regulatable transgene expression in human pluripotent stem cells (hPSCs) and their progenies is often necessary to dissect gene function in a temporal and spatial manner. However, hPSC lines with inducible transgene expression, especially in differentiated progenies, have not been established due to silencing of randomly inserted genes during stem cell expansion and/or differentiation. Here, we report the use of transcription activator-like effector nucleases-mediated targeting to AAVS1 site to generate versatile conditional hPSC lines. Transgene (both green fluorescent protein and a functional gene) expression in hPSCs and their derivatives was not only sustained but also tightly regulated in response to doxycycline both in vitro and in vivo. We modified the donor construct so that any gene of interest can be readily inserted to produce hPSC lines with conditional transgene expression. This technology will substantially improve the way we study human stem cells.

OBJECTIVE: To examine the effect of Ca(2+) store depletion on the translocation of vanilloid transient receptor potential (TRPV) 4-C1 heteromeric channels to the plasma membrane. METHODS AND RESULTS: Vesicular trafficking is a key mechanism for controlling the surface expression of TRP channels in the plasma membrane, where they perform their function. TRP channels in vivo are often composed of heteromeric subunits. Experiments using total internal fluorescence reflection microscopy and biotin surface labeling show that Ca(2+) store depletion enhanced TRPV4-C1 translocation into the plasma membrane in human embryonic kidney 293 cells that were coexpressed with TRPV4 and canonical transient receptor potential 1 (TRPC1). Fluorescent Ca(2+) measurement and patch clamp studies demonstrated that Ca(2+) store depletion enhanced 4α-PDD-stimulated Ca(2+) influx and cation current. The translocation required stromal interacting molecule 1 (STIM1). TRPV4-C1 heteromeric channels were more favorably translocated to the plasma membrane than TRPC1 or TRPV4 homomeric channels. Similar results were obtained in native vascular endothelial cells. CONCLUSIONS: Ca(2+) store depletion stimulates the insertion of TRPV4-C1 heteromeric channels into the plasma membrane, resulting in an augmented Ca(2+) influx in response to flow in the human embryonic kidney cell overexpression system and native endothelial cells.