HSC and progenitor populations in Mll5^−/− bone marrow. (A) Representative FACS data showing LT-HSC (Lin⁻, Sca-1⁺, c-kit⁺, CD34^lo/−, Flt3^lo), ST-HSC (Lin⁻, Sca-1⁺, c-kit⁺, CD34⁺, Flt3 ^lo), MPP (Lin⁻, Sca-1⁺, c-kit⁺, CD34⁺, Flt3⁺), CMP (Lin⁻, Sca-1⁻, c-kit⁺, CD34⁺, FcγR^lo), GMP (Lin⁻, Sca-1⁻, c-kit⁺, CD34⁺, FcγR^hi), MEP (Lin⁻, Sca-1⁻, c-kit⁺, CD34⁻, FcγR^lo), and CLP (Lin⁻, IL-7R⁺, Sca-1^lo, c-kit^lo) populations in an Mll5^−/− mouse and a wild-type littermate. (B) Graph showing the average relative frequencies of the indicated cell types in wild-type and Mll5^−/− mice (n = 7, both groups) determined using the gating strategies shown in panel A. The data were normalized to the wild-type averages and expressed as percentages. Using the Student t test, we discovered that the following populations showed significant differences in frequency between the 2 groups: LT-HSC, ST-HSC, GMP, MEP (all P < .01) and CLP (P < .05). (C) LT-HSC numbers determined in wild-type and Mll5^−/− mice (n = 6, both groups) on the basis of CD34 and Flt-3 or CD150 and CD48 expression. The cells for this experiment were obtained from mice that had been backcrossed 9 times to C57BL/6 partners. The differences in LT-HSC numbers were significant in both cases by Student t test (P < .05).