1. Department of Molecular Medicine, Karolinska Institute (A.F.-M., N.S., P.T.-E., G.N.), 17176 Stockholm, Sweden
2. Department of Biotechnology, KTH Royal Institute of Technology (J.L.), Stockholm 10044, Sweden
3. Institute for Genomic Research (R.L.M., J.Q., N.H.L.), Rockville, Maryland 20850