Galectin-1, but not heparan sulfates, is required for pre-BCR clustering. (A) The level of GAL1 expression in OP9-shG1 cells was evaluated by Western blotting in comparison with OP9-pSR control cells. Relative GAL1 expression level was normalized by comparison with β-actin. (B) Large pre-BII cells were cocultured with OP9-pSR or OP9-shG1 cells. The percentage of cells with a relocalized pre-BCR was determined by confocal microscopy after anti-IgM staining (at least 3 independent experiments). Data are expressed as percentage of inhibition of pre-BCR relocalization, compared with the OP9-pSR control. (C) OP9 stromal cells were preincubated with increasing amount of heparitinase before cocultures with B62c cells; (left) cellular staining with the anti–neo-hep mAb; (right) percentage of cells with a relocalized pre-BCR. Data are representative of 3 independent experiments. Cells (144 to 543) were examined for pre-BCR relocalization in each condition. Errors bars represent SD.