1. School of Information Science and Engineering, University of Jinan, 106 Jiwei Road, 250022 Jinan, P. R. China
2. School of Software, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China
3. Harvard Medical School, Harvard University, P.O. Box 400888, Cambridge, MA 02140, USA
4. National Human Genome Research Institute, National Institutes of Health, US Department of Health and Human Services Bethesda, MD 20852, USA