1. Program in Cancer Genetics, Departments of Oncology and Human Genetics, McGill University, Montreal, Quebec H2W 1S6, Canada.
2. Lady Davis Institute and Segal Cancer Centre, Jewish General Hospital, McGill University, Montreal, Quebec H3T 1E2, Canada.
3. Present address: Faculty of Medicine, University of Toronto, Ontario M5S 1A8, Canada.
4. Present address: Department of Medical Genetics, University of Cambridge, Cambridge CB2 1RZ, UK.
5. Research Institute, McGill University Health Centre, Montreal, Quebec H3G 1A4, Canada.