Molecular genetic investigations of familial Alzheimer disease in a large collaborative data set : ∗P.H. St George-Hyslop, J.L. Haines (Massachusetts General Hospital, Boston, USA), L.A. Farrer (Boston University, Boston, USA), J. Hardy (St Mary's Hospital Medical School, London, UK), C. van Broeckhoven (University of Antwerp, Antwerp, Belgium), D. Crapper McLachlan (University of Toronto, Toronto, Canada), S. Sorbi (University of Florence,