Accelerated onset of a myeloproliferative disorder in the presence of GFI136N. (A) Experimental setup to induce expression of a mutated K-RAS^K12D transgene. (B) Representative bone marrow cytospins of moribund mice with the indicated genotypes (original magnification ×100, Leitz DMRB from Leica, Micropublisher digital color camera, QImaging). (C) Frequency of myeloid and blast cells in healthy (dark bar) and sick mice (white bar). Top panel: Percentage of myeloid cells in the bone marrow (healthy mice: n = 18 Gfi1^+/+, n = 6 Gfi1^36N/36N, n = 3 Gfi1^36S/+, n = 3 Gfi1^36N/+; sick mice: n = 15 Gfi1^+/+, n = 8 Gfi1^36N/36N, n = 5 Gfi1^36S/+, n = 15 Gfi1^36N/+). Middle panel: Number of blast cells per microliter of blood, healthy mice: n = 21 Gfi1^+/+, n = 5 Gfi1^36N/36N, n = 3 Gfi1^36S/+, n = 4 Gfi1^36N/+; sick mice: n = 17 Gfi1^+/+, n = 5 Gfi1^36N/36N, n = 5 Gfi1^36S/+, n = 7 Gfi1^36N/+). Bottom panel: Total number of myeloid cells in the spleen (healthy mice: n = 21 for Gfi1^+/+, n = 3 for Gfi1^36N/36N, n = 3 for Gfi1^36S/+, n = 3 for Gfi1^36N/+; sick mice: n = 16 Gfi1^+/+, n = 8 Gfi1^36N/36N, n = 5 Gfi1^36S/+, n = 14 Gfi1^36N/+). All sick mice carried both the MxCre transgene and the K-RAS^{flstopfl K12D} allele. (D) Kaplan-Meier survival curve of different strains (n = 12 for control mice, n = 22 for Gfi1^+/+, n = 7 for Gfi1^36S/+, n = 22 for Gfi1^36N/+). P ≤ .01 between Gfi1^36N/+ and Gfi1^+/+. P ≤ .04 between Gfi1^36N/+ and Gfi1^36S/+. The cohort of control mice (CTL) was composed of 2 different subgroups. One group (n = 8) consisted of Mx Cre tg Gfi1^flox/flox mice, which were injected with poly(I:C) to exclude that a higher mortality of mice might be related to Cre activation or toxicity of poly(I:C). The second subgroup (n = 6) consisted of wt mice, which were injected with poly(I:C) also to monitor toxic effects of poly(I:C). With the exception of the control mice, all other mice carried an MxCre transgene and a K-RAS^{flstopfl K12D} allele. (E) Approximately 2 × 10⁶ bone marrow cells of moribund mice (see panel D) with the indicated genotypes were transplanted alongside 10⁵ CD45.1⁺ carrier bone marrow cells into sublethally irradiated CD45.1⁺ mice. Mice were then subsequently observed for emergence of disease; n = 3 for all genotypes. *P ≤ .05.