Inducible Hippo kinase deletion in the adult mouse hematopoietic system recapitulates MDS and MPN phenotypes. Recipient mice analyzed in this figure were derived from cells of the following genotypes: Stk4^f/fStk3^f/f;Mx1-Cre⁺ (Stk4^Δ/ΔStk3^Δ/Δ, red), Stk4^f/+Stk3f^/+;Mx1-Cre⁺ (Stk4^Δ/+Stk3^Δ/+, blue), and Stk4^f/fStk3^f/f;Mx1-Cre⁻ (Stk4^+/+Stk3^+/+, green); n = 9 mice per genotype. (A) Experimental schematic depicting generation of bone marrow chimeras and pIpC treatment to induce hematopoietic-specific gene deletion for the indicated genotypes. (B) Gene expression for Stk4 and Stk3 measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR) in flow-sorted Lin⁻ cKIT⁺ hematopoietic progenitor cells derived from 2 representative mice of the indicated genotypes, 2 weeks after completion of pIpC treatment. Peripheral blood white blood cell (WBC) counts (C); peripheral blood platelet counts (D); representative spleens from mice of the indicated genotypes, 6 weeks after pIpC treatment (E); peripheral blood granulocyte counts (F); peripheral blood granulocyte frequencies (G); and peripheral blood MPV (H). (I) Representative Wright-Giemsa–stained peripheral blood smears from mice of the indicated genotypes, 6 weeks after pIpC treatment. Arrowheads indicate abnormally large platelets. Scale bar, 50 μm. (J) Peripheral blood red blood cell (RBC) counts. Data are representative of 2 independent experiments. Homozygous and heterozygous groups were independently tested for statistical significance against controls by multiple t tests with the Holm-Sidak correction. *P < .05, **P < .01, ***P < .001.