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

The roles of Sry-related HMG box (Sox) 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.

Expression of zebrafish SoxF genes were analyzed by whole-mount in situ hybridization, reverse transcription polymerase chain reaction, and real-time reverse transcription polymerase chain reaction of erythroid cells obtained from Tg(gata1:GFP) embryos by fluorescence-activated cell sorting. Roles of SoxF genes were analyzed in zebrafish embryos using morpholino knockdown and analyzed by whole-mount in situ hybridization and real-time reverse transcription polymerase chain reaction. Embryo patterning and vascular development were analyzed.

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 knockdown significantly reduced primitive erythropoiesis at 18 hours post-fertilization (hpf). Definitive hematopoiesis was unaffected. Concomitant sox7 and sox18 knockdown disrupted vasculogenesis and angiogenesis, but not hematopoiesis. sox32 knockdown delayed medial migration of hematopoietic and endothelial progenitors at 18 hpf and abolished cmyb expression at the caudal hematopoietic tissue at 48 hpf. These defects could be prevented by delaying its knockdown using a caged sox32 morpholino uncaged at 10 hpf. Knockdown of SoxF genes significantly upregulated their own expression and that of sox32 also upregulated sox18 expression.

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.