Sf3b1K700E, Srsf2P95H, HSC-Scl-CreERT, Rosa26-Lox-STOP-Lox-Cas9-EGFP, Tet2 floxed, and Mx1-cre mice were obtained from The Jackson Laboratory and were previously generated and described13 (link),19 (link),26 (link) with the exception of HSC-Scl-CreERT mice44 (link) (which were obtained from Dr. Joachim R Göthert).