CALR mutants induce an ET-like phenotype in vivo in mice. Primary CALRdel52 (n = 22), CALRins5 (n = 20), CALRdelex9 (n = 10), CALRwt (n = 22), and Mock (n = 10) recipient mice were analyzed every 3 weeks after bone marrow transplantation (BMT), over a 1-year period. Graphs show (A) platelets with a smaller scale on the right, (B) RBC and (C) WBC counts as mean ± SEM. Bonferroni multiple comparison test: *P < .05, **P < .001, ***P < .0001. Arrows indicate 6 months posttransplantation. (D) Spleen GFP⁺ Lin⁻ cells were examined by western blot for CALR protein levels using an antibody specifically directed against the novel C-terminal tail of the mutants (CALRmut). An antibody directed against the whole CALR protein (CALRtot) was also used. β-actin serves as a loading control. Blots show representative results. ns, a nonspecific band; SEM, standard error of the mean.