1. Department of Biochemistry, The University of Western Ontario, London, Ontario N6A 5C1, Canada
2. Department of Genome Sciences, University of Washington, Seattle, Washington 98195, United States
3. Department of Biology, The University of Western Ontario, London, Ontario N6A 5C1, Canada
4. Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario N6A 5C1, Canada