Enables DNA-binding transcription activator activity, RNA polymerase II-specific; RNA polymerase II cis-regulatory region sequence-specific DNA binding activity; and RNA polymerase II-specific DNA-binding transcription factor binding activity. Involved in several processes, including heart development; regulation of transcription by RNA polymerase II; and visceral motor neuron differentiation. Acts upstream of or within several processes, including circulatory system development; negative regulation of SMAD protein complex assembly; and regulation of transcription, DNA-templated. Located in cytoplasm and nucleus. Is expressed in several structures, including early conceptus; genitourinary system; heart; hindbrain; and sensory organ. Used to study dilated cardiomyopathy. Human ortholog(s) of this gene implicated in atrial heart septal defect 4. Orthologous to human TBX20 (T-box transcription factor 20). [provided by Alliance of Genome Resources, Apr 2022]