A conditional knock-in mouse with heterozygous expression of SF3B1-K700E causes progressive macrocytic anemia (27), and a knock-in mice with hematopoietic-specific expression of SF3B1-K700E impaired erythropoiesis and progressive anemia without ringed sideroblasts, accompanied by a reduction in hematopoietic stem cells (26). Here, SF3B1 is linked to macrocytic anemia.