1. Howard Hughes Medical Institute, Department of Biomedical Engineering and Center of Synthetic Biology, Boston University, Boston, MA 02215, USA.
2. Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02118, USA.
3. Program in Molecular Biology, Cell Biology, and Biochemistry, Boston University, Boston, MA 02215, USA.
4. Boston University School of Medicine, 715 Albany Street, Boston, MA 02118, USA.