Fig. 1

Pluripotent very small embryonic-like stem cells (VSELs) in adult mouse bone marrow. a Expression of pluripotent stem cell makers including nuclear OCT-4 (red) and SOX-2 (red) and cell surface SSEA-1 (green) and SCA-1 (green) were detected on small-sized cells in bone marrow smears. Also note presence of cytoplasmic OCT-4 in slightly bigger cells. These cells were more abundant and please refer to Additional file 1: Figure S1 to see additional images of cytoplasmic OCT-4-expressing cells. Scale bar = 20 μm. b Flow cytometry analysis of VSELs and HSCs in bone marrow. Cells of size 2–8 μm were gated using size calibration beads as reference, followed by sequential selection of LIN^–/SCA-1⁺ cells. This population was evaluated for expression of CD45. The LIN^–/SCA-1⁺/CD45^– cells were VSELs, while LIN^–/SCA⁺/CD45⁺ cells were HSCs. The average percentage of VSELs and HSCs with SD from 10 experiments is reported. Representative image is shown. c Dual immunofluorescence was performed using anti-SSEA1 antibody (green) with nuclear OCT-4 (red, upper) and SCA-1 (red, lower). Cells co-expressing nuclear OCT-4 and SSEA-1 and SSEA-1 and SCA-1 were observed. Scale bar = 20 μm. In all images, nuclei are counterstained with DAPI. HSC Hematopoietic stem cell, OCT-4 octamer binding transforming factor-4, SSEA-1 stage-specific embryonic antigen-1, Sca-1 stem cell antigen-1, Sox 2 sex-determining region (box 2), DAPI 4′,6-diamidino-2-phenylindole (Color figure online)