Fig. 7. Non-cell autonomous requirement for bls in primitive hematopoiesis. Donor cells labeled with biotin-dextran were transplanted into unlabeled hosts at the sphere stage, to determine whether donor cells can contribute to blood in the host environment. The resulting chimeric animals were analyzed for gata1 expression. Genotype of the host is indicated outside, and that of the donor within, the parenthesis (host genotype 
(donor genotype)). Donor-derived cells were detected by avidine-peroxidase color reaction, and appear brick red. Cells containing gata1 transcripts appear blue. Donor cells that contribute to blood will be colored with red and blue, appearing dark purple (arrowheads).
