Cover photograph (Copyright © 2006, American Society for Microbiology. All Rights Reserved.): The intracellular tyrosine kinase PTK6 is expressed in villus epithelial cells in small intestine. Immunohistochemistry was performed with adult wild-type mouse jejunum using anti-PTK6 (Sik) antibodies, and antibody binding was detected with the peroxidase substrate DAB (brown). (See related article on page 4949.)