Acts as a transcription regulator that binds target promoter DNA (PubMed:33952808). Binds to the sequences 5'-AACAAT-'3 or 5'- AACAAAG-3'. Modulates transcriptional regulation via WNT3A. Inhibits Wnt signaling. Promotes degradation of activated CTNNB1. Plays a key role in the regulation of embryonic development. Required for normal development of the definitive gut endoderm. Required for normal looping of the embryonic heart tube. Plays an important role in embryonic and postnatal vascular development, including development of arteries. Plays an important role in postnatal angiogenesis, where it is functionally redundant with SOX18. Required for the generation and maintenance of fetal hematopoietic stem cells, and for fetal hematopoiesis. Probable transcriptional activator in the premeiotic germ cells. {ECO:0000250|UniProtKB:Q61473, ECO:0000269|PubMed:33952808}. This is the function of SOX17 (SRY-box transcription factor 17, Ensembl gene identifier ENSG00000164736).