SOX17, also known as Transcription factor SOX-17, is, as the name suggests, a transcription factor and a probable transcriptional activator in the premeiotic germ cells. It belongs to the SRY-related HMG box family of transcription factors with a high-mobility group DNA-binding domain (HMG box) that plays a key role in embryogenesis and binds to the sequences 5'-AACAAT-'3 or 5'-AACAAAG-3'. SOX17 plays an essential role in cardiac mesoderm specification as well as in definitive hematopoiesis, maintaining fetal hematopoietic stem cells, hematopoiesis in the fetal liver and yolk sac. Along with beta-catenin it is known to cooperate in the regulation of transcription of endodermal genes. Defects in SOX17 are known to cause a severe defect in fetal hematopoiesis.