TAM cells engrafted in NOG mice. (A) Proportion of human CD45⁺ cells in the BM of NOG mice at 4, 8, and 12 weeks after transplantation (n = 3–5 per group). (B) May-Giemsa staining of the BM smear of patients and cytospin preparation of human CD45⁺ cells in the recipient NOG mice. Blast cells with cytoplasmic blebbing consistent with megakaryocytic differentiation were present in the BM of recipient mice. (C) Surface marker analysis of engrafted TAM cells. Human CD45⁺ TAM-derived cells expressing hCD117, hCD34, hCD33, and hCD41a are detected in the recipient’s BM. Blast cells were identified by CD45/SSC gating, and debris (low forward scatter) and dead cells (4′,6-diamidino-2-phenylindole positive) were excluded from the analysis. A representative result of >3 experiments is shown. (D) Genomic direct sequencing shows the presence of concordant GATA1 mutation in xenograft and original patients (1 and 2). (E) G-band karyotyping of TAM-derived cells in recipient murine BM shows no additional chromosome abnormality apart from constitutional trisomy 21, consistent with the findings in the original patients. The GATA1 mutation and the karyotype of engrafted cells from patient 9 were not assessed because of a low cell number.