1 Department of Cell and Developmental Biology, Epithelial Biology Center, Vanderbilt University School of Medicine, Nashville, Tennessee.
2 Department of Cell and Developmental Biology, Epithelial Biology Center, Vanderbilt University School of Medicine, Nashville, Tennessee. Electronic address: ken.s.lau@vanderbilt.edu.
3 Department of Cell and Developmental Biology, Epithelial Biology Center, Department of Surgery, Vanderbilt University School of Medicine, Nashville VA Medical Center, Nashville, Tennessee. Electronic address: jim.goldenring@vanderbilt.edu.