About the Authors
Dipartimento di Genetica e Microbiologia “Adriano Buzzati-Traverso”, Università di Pavia, Pavia, Italy
The authors have declared that no competing interests exist.
Conceived and designed the experiments: EG. Performed the experiments: FMP SGN EM LK. Analyzed the data: FMP SGN LB ER EG. Contributed reagents/materials/analysis tools: CA. Wrote the paper: ER EG. Contributed to paper preparation: FMP SGN.