Enables DNA-binding transcription repressor activity, RNA polymerase II-specific and RNA polymerase II cis-regulatory region sequence-specific DNA binding activity. Involved in blood vessel development; negative regulation of DNA-binding transcription factor activity; and negative regulation of transcription by RNA polymerase II. Acts upstream of or within neuromuscular process controlling balance and regulation of growth. Located in nucleus. Is expressed in several structures, including cardiovascular system; ganglia; genitourinary system; hemolymphoid system gland; and yolk sac. Orthologous to human FOXS1 (forkhead box S1). [provided by Alliance of Genome Resources, Apr 2022]