The Role of Sox Genes (Group F) in Zebrafish Hematopoiesis

Abstract

Introduction: Sry-related HMG box (SOX) genes belong to a family of transcription factors sharing a conserved high-mobility-group domain. However, information about the functions of Group F sox genes (sox 7, 17, 18 and sox32), particularly in hematopoiesis, are scarce. This is addressed in the present study using morpholino gene knockdown in zebrafish. Method: Morpholinos (MO) targeting selected sox genes were injected into zebrafish embryos and were analyzed for effects in hematopoiesis using real time RT-PCR and WISH. Results: Sox17 was expressed in neural tube and intermediate cell mass (ICM) while sox7 and sox18 was enriched in the vasculature. Sox32, unique in teleosti, was expressed predominantly in the posterior ICM. Of the four, only sox17 was highly enriched in FAC sorted gata-1 positive cells. Injection of Sox17 MO resulted in significant decrease in alpha embryonic hemoglobin (Į-eHB) and gata-1 expression which can be reconstituted by co-injecting only sox17 transcripts, but not by sox7, sox18 or sox32 transcripts. Co-injection of Sox7 and Sox18 MO had no effect on Į-eHB expression. Knockdown of sox32 resulted in decrease of Į-eHB expression, likely to be due to abnormal embryo patterning. Cell cycle profile of gata-1 positive cells in sox17 morphants showed an increase in the percentage of cells in the G1 phase. While either knockdown or over-expression of this gene have no effect on ȕ-catenin signaling as shown by the Tg(Top:GFP)w25 transgenic zebrafish embryos. Conclusion: Of the four SoxF genes in zebrafish, sox17 have unique role in primitive erythropoiesis, enhancing the transition of these cells through the G1 phase. Unlike other orthologs, zebrafish sox17 have no effect on ȕ-catenin signaling. Therefore this gene was unlikely to effect the proliferation of erythroid cells in zebrafish embryos through this pathway.