1. Division of Medical Genetics, Department of PediatricsDuke University Medical CenterDurhamNorth CarolinaUSA
2. Department of PediatricsMcMaster University Medical CenterHamiltonOntarioCanada
3. Department of MedicineMcMaster University Medical CenterHamiltonOntarioCanada
4. Department of PathologyGenzyme Corp.FraminghamMassachusettsUSA