Zebrafish von Hippel-Lindau (vhl) tumor suppressor mutants compared to siblings at 7 dpf

We have generated two zebrafish lines carrying inactivating germline mutations in the von Hippel-Lindau (VHL) tumor suppressor gene ortholog vhl. Mutant embryos display a general systemic hypoxic response, including the upregulation of hypoxia-induced genes by 1 day post-fertilization and a severe hyperventilation and cardiophysiological response. vhl mutants develop polycythemia with concomitantly increased epo/epor mRNA levels and Epo signaling. In situ hybridizations reveal global up-regulation of both red and white hematopoietic lineages. Hematopoietic tissues are highly proliferative, with enlarged populations of c-myb+ HSCs and circulating erythroid precursors. Chemical activation of Hif-signaling recapitulated aspects of the vhl-/- phenotype. Furthermore, microarray expression analysis confirms the hypoxic response and hematopoietic phenotype observed in vhl-/- embryos. We conclude that Vhl participates in regulating hematopoiesis and erythroid differentiation. Injections with human VHLp30 and R200W mutant mRNA demonstrate functional conservation of VHL between mammals and zebrafish at the amino acid level, indicating that vhl mutants are a powerful new tool to study genotype-phenotype correlations in human disease. Zebrafish mutants are the first congenital embryonic viable systemic vertebrate animal model for VHL, representing the most accurate model for VHL-associated polycythemia to date. They will contribute to our understanding of hypoxic signaling, hematopoiesis and VHL-associated disease progression. We have compared gene expression profiles between pooled zebrafish vhl mutants and siblings from four different transheterozygous (hu2081/+ x hu2117/+) clutches at 7 days post-fertilization. Samples were run in dye-swap. Results were validated by whole mount in situ hybridization.