Ts65Dn bone marrow displays signs of disease by 3 months of age. (A) Three- to 4-month-old Ts65Dn mice harbor a larger LSK cell compartment compared with euploid controls. n = 9 Ts65Dn; n = 9 euploid controls. (B) Bone marrow LSK cells express more CD34 in young Ts65Dn mice. (C) Representative pyronin Y/Hoechst staining of Ts65Dn LSK cells shows that they are more transcriptionally active than controls. Numbers on plots represent the percentage of the total population of cells in the rectangle. (D) Average values and statistical analysis of quiescent LSK cells in bone marrow. n = 3 Ts65Dn; n = 3 controls. P = .001. (E) Young Ts65Dn mice display a trend toward increased megakaryocyte progenitors in the spleen. represent euploid controls; represent Ts65Dn. n = 9 Ts65Dn; n = 9 controls. Error bars represent SE.