Characterization of Sry-related HMG box group F genes in zebrafish hematopoiesis

OBJECTIVE: The roles of Sox (Sry-related HMG box) genes in zebrafish hematopoiesis are not clearly defined. In this study, we have characterized the sequence homology, gene expression, hematopoietic functions and regulation of sox genes in F group (SoxF) in zebrafish embryos. MATERIALS AND METHODS: Expression of zebrafish SoxF genes were analyzed by whole-mount in situ hybridization (WISH), RT-PCR and real-time RT-PCR of erythroid cells obtained from Tg(gata1:GFP) embryos by FACS. Roles of SoxF genes were analyzed in zebrafish embryos using morpholino knock-down and analyzed by WISH and real-time RT-PCR. Embryo patterning and vascular development were analyzed. RESULTS: All members except sox17 contained a putative β-catenin binding site. sox7 and 18 expressed primarily in the vasculature. sox17 expressed in the intermediate cell mass and its knock-down significantly reduced primitive erythropoiesis at 18 hour post-fertilization (hpf). Definitive hematopoiesis was unaffected. Concomitant sox7 and sox18 knock-down disrupted vasculogenesis and angiogenesis but not hematopoiesis. sox32 knock-down delayed medial migration of hematopoietic and endothelial progenitors at 18hpf and abolished cmyb expression at the caudal hematopoietic tissue at 48 hpf. These defects could be prevented by delaying its knock-down using a caged sox32 morpholino uncaged at 10hpf. Knock-down of SoxF genes significantly up-regulated its own expression and that of sox32 also up-regulated sox18 expression. CONCLUSION: sox17 helped to maintain primitive hematopoiesis whereas sox7 and sox18 regulated angiogenesis and vasculogenesis. sox32 affected both vascular and hematopoietic development, through its effects on medial migration of the hematopoietic and endothelial progenitors.