1. Department of Genomics and Bioinformatics, Centre for Genomic Regulation (CRG) The Barcelona Institute of Science and Technology Dr. Aiguader 88, Barcelona 08003 Spain
2. Department of Experimental and Health Sciences, Universitat Pompeu Fabra (UPF) 08003 Barcelona Spain
3. ICREA, Pg. Lluís Companys 23 08010 Barcelona Spain