Expression of antigen CD41a and scinderin in normal human bone marrow cells, cell lines, and cells from patients with acute megakaryoblastic leukemia.

(A) Schematic representation of scinderin (Sc) domains 1 to 6 shows amino acid sequences corresponding to the 3 actin-binding sites (Sc-ABS₁, Sc-ABS₂, and Sc-ABS₃) and to the 2 PIP₂-binding sites (Sc-PIP₂BS₁ and Sc-PIP₂BS₂). (B) Two normal human bone marrow (BM) preparations were treated with NH₄Cl and EDTA, as indicated in “Materials and methods,” and they were cytospun onto glass slides. An enriched preparation of CD34⁺/CD38⁺ cells was isolated from human bone marrow and cultured in the presence of TPO, IL-3, and IL-6, as indicated in “Materials and methods.” A colony (CFU-MK) formed after 12 days in culture is shown. BM samples from 3 patients (patients 1, 2, and 3) with M7 acute megakaryoblastic leukemia were cytospun onto glass slides. Two of the samples were from patients with Down syndrome (patients 2 and 3). Patients 1 and 2 had low levels of CD41a staining. Patient 3 had much higher levels of CD41a staining and cells that appeared to be more mature than those in the other 2 patients. Cell lines MEG-01, HEL, NS-MEG, K562, and HL-60 were also grown in culture as described in “Materials and methods,” and cell samples from the cultures were cytospun onto glass slides. All preparations were fixed and double stained with antibodies against scinderin and CD41a, as indicated in “Materials and methods.” PC, phase-contrast microscopy. Horizontal bars, 15 μm.