[1] Univ Calif Davis, Dept Comparat Med, Ctr Comparat Med, Davis, CA 95616 USA
[2] Univ Calif Davis, Sch Med, Dept Med Pathol & Lab Med, Sacramento, CA 95817 USA
[3] NCI, Lab Populat Genet, Div Canc Epidemiol & Genet, NIH, Bethesda, MD 20892 USA
[4] Univ Calif San Francisco, Dept Neurol Surg, San Francisco, CA 94143 USA
[5] Univ Calif Davis, Sch Med, Dept Biochem & Mol Med, Sacramento, CA 95817 USA
[6] McGill Univ, Royal Victoria Hosp, Mol Oncol Grp, Montreal, PQ H3A 1A1, Canada