FIG 10.

Mice transplanted with Sec23b^−/− FLC do not exhibit an erythroid phenotype. Lethally irradiated UBC-GFP^tg/+ mice were transplanted with GFP⁻ FLC harvested from either Sec23b^−/− or WT E.16.5 embryos. Reconstituted hematopoietic cells in recipient mice were GFP⁻, confirming donor engraftment. Recipients of Sec23b^−/− FLC had indistinguishable RBC counts (A), hemoglobin (B), and hematocrit (C) levels compared to control recipients of WT FLC. (D and E) Sec23b^−/− RBC ghosts did not exhibit a band 3 glycosylation defect by Western blotting (D), nor did Ter119⁺ erythroid precursors demonstrate a “double membrane” by transmission electron microscopy (E). (F) By FACS analysis, Ter119⁺ erythroid cells comprised 36.67% (±16.69% [SD]) and 41.56% (±17.68%) of total live BM cells harvested from mice transplanted with Sec23b^−/− and WT FLC, respectively. (G) Mice transplanted with Sec23b^−/− FLC did not exhibit an increase in the percentage of bi/multinucleated RBC precursors. (H) BM erythroid compartments were stratified by forward scatter and CD71 expression into 5 stages of erythroid development (stages I through V, in chronological order) (22). The distributions of erythroid cells among stages I through V were comparable in mice transplanted with Sec23b^−/− FLC and mice transplanted with WT FLC. Error bars indicate standard deviations. Means and standard deviation are indicated by horizontal lines.