1. Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
2. Department of Medicine, Division of Gastroenterology and Hepatology, Stanford School of Medicine, Stanford, California, USA
3. Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
4. VA Palo Alto Health Care System, Department of Veterans Affairs, Palo Alto, California, USA