Hdac1 inhibitory function of largazole was evaluated in zebrafish angiogenic models. (a,b) Larvae treated with 500 nM largazole displayed blood pooling and pigment pattern defects, similar to that of hdac1 mutant, colgate phenotype. (c,d) To mimic pathogenic vascular defects, vhlhu2117 mutants exhibiting an increased vascularization were used. 2 μM largazole had little effect on basal vascularization of the wildtype embryo (e), while the vhlhu2117 vascularization was greatly minimized in the tail (f-h). The numbers of larvae showing the mutant phenotype after largazole treatment is significantly less than the expected 25% (p<0.01; Chi squared test; n=56 (DMSO), n=44 (Largazole)).