Deletion of Tet2 alters HSC compartments in mice before their development of myeloid malignancies as well as HSC proliferation and differentiation potential in vitro. (A) Flow cytometric analysis of LSK (Lin^–Sca-1⁺Kit⁺) HSC and LK (Lin^–Sca-1⁻Kit⁺) progenitor cell population in a representative preleukemic 6- to 7-week-old Tet2^−/− mice. (B) The percentage of LSK cells within the Lin⁻ cell populations in the BM of preleukemic Tet2^−/−, Tet2^+/−, and WT control mice (average ± SD of 4-8 animals). (C-E) The proliferation and differentiation potential of various genotypes of LSK cells were examined by culturing 500 LSK cells in the presence of 4 growth factors and assaying their ability to generate total cells (C) and CFCs (D) after 7 days of culture. CFCs in each culture were evaluated by colony assay of a fraction of the cultures. Cytospin preparations of the progenies generated from each genotype of LSK cells after 7 days of culture were stained with May-Giemsa, a 200-cell differential was performed (E). Representative data from 2 separate experiments are shown. ***P < .001.