[1] Natl Univ Singapore, Yong Loo Lin Sch Med, Dept Physiol, Singapore 117593, Singapore
[2] Univ Calif San Diego, Dept Cellular & Mol Med, Stem Cell Program, La Jolla, CA 92093 USA
[3] Univ Calif San Diego, Inst Genom Med, La Jolla, CA 92093 USA
[4] ASTAR, Mol Engn Lab, Singapore 138673, Singapore