1. School of Biochemistry and Division of Medical Science, School of Medicine, University of Birmingham, Birmingham, B15 2TT, United Kingdom, Imperial College School of Medicine at NHLI, London, SW3 6LY, United Kingdom, Division of Medical and Molecular Genetics, King's College, Guy's Hospital, London SE1 9RT, United Kingdom, and CRBM, CNRS, INSERM U249, F-34090 Montpellier, France