Specification of Definitive Hematopoietic Stem Cells Requires scl-β but Not scl-α (A–F) WISH of definitive hematopoietic stem cell markers c-myb (A–C) and runx1 (D–F). Expression of c-myb and runx1 in the ventral wall of DA was markedly reduced in 30-hpf scl-β morphants (C and F) but not in 30-hpf control embryos (A and D) or scl-α morphants (B and E). Insets are high-magnification (20×) views of the ventral wall of DA. The arrowheads indicate the definitive hematopoietic stem cells along the ventral wall of DA. (G–I) WISH of T cell marker rag1. rag1 expression in thymic T cells was abolished in 5-dpf scl-β morphants (I) but not in control embryos (G) and scl-α morphants (H). Arrows indicate the thymus region. In all panels, embryos are in lateral view with anterior to the left.
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