Addresses: *The Van Andel Research Institute, 333 Bostwick, Grand Rapids, MI 49503, USA. †The University of Amsterdam, Department of Molecular and Cell Biology, 1081 BT Amsterdam, The Netherlands. ‡The University of Michigan Medical School, 1500 East Medical Center Drive, Ann Arbor, MI 48109, USA. §Yale University School of Medicine, Department of Pathology, 310 Cedar Street, New Haven, CT 06510, USA. Correspondence: Brian B Haab. E-mail: Brian.Haab@vai.