Question

4. (5 points) Only cells that express a puromycin-resistance (PR) gene can grow in the presence of the drug puromycin. Ganciclovir is a nontoxic drug that is converted to a lethal toxin in a cell that expresses thymidine kinase (TK). Thy-1 is a fibroblast-specific marker protein. Which of the following selection strategies is the most reasonable one to use in experiments that attempt to generate induced pluripotent stem cells (iPS cells) from fibroblasts (1 point, letter)? Explain your choice (4 points, 2-3 sentences).

1. Engineering fibroblasts to express PR under the control of the Nanog promoter, and selecting iPS cells in puromycin-containing media
2. Engineering fibroblasts to express PR under the control of the Thy-1 promoter, and selecting iPS cells in puromycin-containing media
3. Engineering fibroblasts to express TK under the control of the Nanog promoter, and selecting iPS cells in ganciclovir-containing media
4. Engineering fibroblasts to express TK under the control of the Thy-1 promoter, and selecting iPS cells in ganciclovir-containing media
5. Engineering fibroblasts to express TK under the control of the Thy-1 promoter, and selecting iPS cells in puromycin-containing media

Answer 1

The correct option will be- D- Engineering fibroblasts to express TK under the control of the Thy-1 promoter, and selecting iPS cells in ganciclovir-containing media

Explanation: Since Thy-1 promoter is fibroblast specific marker its promoter will provide ability to express the thymidine kinase when cells are in fibroblast stage. Generated induced pluripotent cells from fibroblasts will not express thymidine kinase and presence of Ganciclovir in media will be converted into lethal toxin for thymidine kinase (TK) expressing fibroblasts and only the nduced pluripotent cells will grow helping out in their selection.