The proteins involved in Ca²⁺ signaling in the patients exhibit similarities with immature megakaryocytes. (A) CD34⁺CD41⁺ cells isolated from both umbilical cord blood (left) and leukapheresis (right) samples were purified by fluorescence-activated cell sorting at day 8 of culture. Three different sorted cell samples were cultured for either up to 14 or to 16 to 17 days, and cells were examined at times shown in the figure. Proteins were treated for WB to detect the same SERCA and PMCA-type Ca²⁺ ATPases and control proteins as in Figure 5, as well as PARP (n = 5). The intensity of the bands was quantified by densitometry and the mean values obtained at days 8 or 9 were arbitrarily taken as 100% (Figure S1). (B) The summary of densitometric measurements was used to draw the schematic representation of the relative expressions of PMCA4b, SERCA3a, and β3 during megakaryocytopoiesis (left), and in platelets of the patients (right).