About the Authors
Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
Department of Biology, York University, Toronto, Ontario, Canada
The authors have declared that no competing interests exist.
Conceived and designed the experiments: FS TSA SW LF. Performed the experiments: FS TSA SW MNH YS. Analyzed the data: FS TSA SW MNH. Wrote the paper: FS LF.