The SH2 domain is required for the induction of a JAK2V617F-driven MPN and myelofibrosis in a murine BM transplantation model. (A) Three independent transplantation experiments were performed. Results of one representative transplantation are depicted. Murine BM was retrovirally infected with JAK2V617F (V617F, n = 4), JAK2V617F+R426K (V617F mSH2, n = 3), or empty vector (mock, n = 2) and transplanted into lethally irradiated syngenic recipient mice. Hematocrit (%), hemoglobin (g/dL), platelets (G/L), WBC (G/L), and reticulocytes (‰) of transplanted mice at the indicated time points after transplantation are shown. (B) Spleens of representative transplanted animals are shown (left panel), and spleen size was quantified by weight (mg). Values are expressed as mean ± SEM of all animals transplanted. (C) The histopathologic analysis (hematoxylin and eosin staining, ×400) revealed hyperplastic, left-shifted myelopoiesis, and clusters of megakaryocytes in the spleens of JAK2V617F mice, whereas spleens of mock and JAK2V617F mSH2 mice showed normal cellularity. (D) Hematoxylin and eosin and reticulin stainings as labeled of representative tissue samples are shown (×400): left (mock) a normal cellular BM is shown. Note, that all hematopoietic cell lines are present, and the amount of BM fibers is normal. In the middle, BM from a JAK2V617F (V617F) mouse is shown, displaying a left-shifted increase of myeloid cells and a marked presence of collagen fibers, similar to the increase of reticulin fibers in human myeloproliferative disorders. BM obtained from JAK2V617 mSH2 (V617F mSH2) mice shows cellularity and fiber distribution nearly identical to the mock mice shown on the left. Slides were viewed with a Zeiss Axioplan 2 microscope (40×/0.75NA Plan-Neofluar air objective). Images were acquired using a Zeiss Axiocam MRc 5 camera and were processed with Axiovision Rel 4.6 scanning software.