BrdU incorporation assay in wild-type and Vhl^−/− zebrafish. Increased cell proliferation is detectable in all hematopoietic tissues of Vhl^−/− embryos 7.5 days after fertilization, as shown in whole mount and cross-sections (original magnification ×20). CHT indicates caudal hematopoietic tissue; and PHT, pronephric hematopoietic tissue. See the complete figure in the article beginning on page 6449.