About the Authors
Department of Biological Sciences and Temasek Life Sciences Laboratory, National University of Singapore, Singapore
The authors have declared that no competing interests exist.
The author(s) have made the following declarations about their contributions: Conceived and designed the experiments: LL CL HY. Performed the experiments: LL CL XH WX LS ZT YW. Analyzed the data: LL CL XH WX LS ZT YW HY. Contributed reagents/materials/analysis tools: LL CL XH WX LS ZT YW. Wrote the paper: LL CL HY.