1. Division of Gastroenterology Department of Medicine Brigham and Women's Hospital Harvard Medical School Boston MA 02115 USA
2. The David H. Koch Institute for Integrative Cancer Research Massachusetts Institute of Technology Cambridge MA 02139 USA
3. Department of Health Sciences and Technology Eidgenössische Technische Hochschule Zürich Universitätstrasse 2 Zurich 8092 Switzerland
4. Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge MA 02139 USA
5. Department of Cell/Cellular and Molecular Biology Northeastern University Boston MA 02115 USA
6. Department of Bioengineering Northeastern University Boston MA 02115 USA
7. Department of Biotechnology Northeastern University Boston MA 02115 USA
8. Division of Comparative Medicine Massachusetts Institute of Technology Cambridge MA 02139 USA