Polycistronic lentiviral vector for hit and run reprogramming of mouse and human somatic cells to induced pluripotent stem cell.

摘要

Embryonic stem (ES) cells are pluripotent and, therefore, can differentiate into most if not all somatic cell types. Because of this characteristic, ES cells have great potential for medical therapies. Since the first cloned mammal, Dolly the sheep, was published in 1996 (1), several groups have successfully cloned other animals by the same nuclear transfer method (2). Isogenic ES cell lines can also be established from donor cells by the same technique (3). However, to date there has been no report of successful derivation of human ES cells by nuclear transfer. Based on the cell fusion (4) and nuclear transfer results, it was believed that factors in the oocyte and ES cells might have the ability to reprogram somatic cells to a more un-differentiated cell type. In 2006, by retroviral expression of 4 different factors in mouse fibroblasts, Yamanaka's group reprogrammed those cells to a ES-like cell type, also known as induced pluripotent stem (iPS) cells (5). A year later, human iPS cells were successfully derived by two different groups (6,7). Since 2007, many groups have demonstrated that iPS cells, just like ES cells, can differentiate into different mature somatic cells (8,9), and the therapeutic potential of these cells has been proven in a mouse model of sickle cell disease (10). However, there are some potential risks when using iPS cells for therapy. First, some of the reprogramming factors are potential oncogenes (11,12). Although the transgenes are usually silenced after iPS cells are formed, reactivation is possible. Second, using four different viruses to infect cells generates multiple insertion sites(13), and these insertional mutants may disrupt normal gene function. Here, we describe a clinically safer way to derive iPS. By using a single polycistronic lentiviral vector, we reprogrammed mouse and human somatic cells to pluripotent stem cells. The reprogramming transgenes are removed after iPS cells are formed. Insertion sites were cloned, sequenced and mapped to the genome. These insertions did not disrupt any exons or know regulatory elements. In future experiments, I plan to utilize the polycistronic vector to develop a novel treatment for human acquired immunodeficiency syndrome.