1. Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain
2. Institució Catalana de Recerca i Estudis Avançats (ICREA), 23 Passeig Lluís Companys, Barcelona 08010, Spain
3. Universitat Pompeu Fabra (UPF), Department of Experimental and Health Sciences, Barcelona 08003, Spain
4. Department of Biology ‘Charles Darwin’, Sapienza University of Rome, P.le A. Moro 5, Rome 00185, Italy