European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SD, United Kingdom.|Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain.|European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SD, United Kingdom.|Unité Bioinformatique Evolutive, Centre de Bioinformatique, Biostatistique et Biologie Intégrative (C3BI)-USR 3756 CNRS and Institut Pasteur, Paris, France.|Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain.|Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain.