Transduction of human embryonic stem cells by foamy virus vectors

Human embryonic stem cells (hESCs) are important tools for the study of stem cell biology and may ultimately be used in cellular therapies and regenerative medicine. For hESCs to achieve their potential, stable genetic modification of the hESC genome will be required. Here we have studied the transduction of hESCs by vectors based on foamy virus (FV), an integrating retrovirus with no known pathogenicity. We find that hESCs and also ESCs derived from rhesus monkeys can be efficiently transduced by FV vectors at frequencies of 14-48%. Integration of FV vector DNA was demonstrated by Southern blot analysis, and stable expression was observed from a single integrated provirus in several clones. Transduced hESCs expressed markers characteristic of undifferentiated cells, differentiated and expressed markers from all three germ layers after serum exposure, and formed teratomas with persistent transgene expression in differentiated cells. Thus, FV vectors are promising tools for the genetic modification of hESCs.