Enables several functions, including E-box binding activity; protein heterodimerization activity; and transmembrane receptor protein tyrosine kinase activator activity. Contributes to DNA-binding transcription activator activity, RNA polymerase II-specific. Involved in gastrulation; positive regulation of neuron differentiation; and positive regulation of transcription by RNA polymerase II. Acts upstream of or within several processes, including histone acetylation; immune system development; and regulation of gene expression. Located in cytosol and nucleus. Part of RNA polymerase II transcription regulator complex and nucleosome. Is expressed in several structures, including branchial arch; central nervous system; male reproductive system; retina; and urinary system. Human ortholog(s) of this gene implicated in agammaglobulinemia and colorectal cancer. Orthologous to human TCF3 (transcription factor 3). [provided by Alliance of Genome Resources, Apr 2022]