European University of Madrid 2 articles published in JoVE Developmental Biology Tracing Gene Expression Through Detection of β-galactosidase Activity in Whole Mouse Embryos María José Blanco*1, Ana I.R. Learte*1, Miguel A. Marchena1, Emma Muñoz-Sáez1, María Antonia Cid1, Iván Rodríguez-Martín1, Cristina Sánchez-Camacho2,3 1Faculty of Biomedical and Health Sciences, Universidad Europea de Madrid, 2Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 3School of Doctoral Studies and Research, Universidad Europea de Madrid Here we describe the standard protocol for the detection of β-galactosidase activity in early whole mouse embryos and the method for paraffin sectioning and counterstaining. This is an easy and quick procedure to monitor gene expression during development that can also be applied to tissue sections, organs or cultured cells. Immunology and Infection Methodology for the Study of Horizontal Gene Transfer in Staphylococcus aureus Fabio Cafini*1,2, Nguyen Thi Le Thuy*3, Federico Román4, José Prieto5, Sarah Dubrac6,7, Tarek Msadek6,7, Kazuya Morikawa1 1Division of Biomedical Science, Faculty of Medicine, University of Tsukuba, 2Department of Basic Biomedical Science, Universidad Europea de Madrid, 3Human Biology Program, School of Integrative and Global Majors, University of Tsukuba, 4Laboratory of Nosocomial Infections, Department of Bacteriology, Centro Nacional de MicrobiologÍa, Instituto de Salud Carlos III, 5Division of Microbiology, Department of Medicine, School of Medicine, Universidad Complutense, 6Biology of Gram-Positive Pathogens, Department of Microbiology, Institut Pasteur, Paris, France, 7ERL3526, CNRS, Paris, France We describe here three different protocols for the in vitro investigation of conjugation, transduction, and natural transformation in Staphylococcus aureus.