Transcription factor essential for neural and some non-neural tissues development. Binds to an 11-bp consensus sequence containing the invariant tetranucleotide 5'-ACGC-3'. During development of the central nervous system, required to specify the amacrine and horizontal cell fates from multipotent retinal progenitors while suppressing the alternative photoreceptor cell fates. Drives commitment of p2 progenitors to the V2b interneuron fates during spinal cord neurogenesis. In development of non-neural tissues, plays an essential role in the specification of the atrioventricular canal. Isoform 1 is expressed mainly in adult thymus. Isoform 2 is detected in adult skin. Isoform 3 is expressed in adult brain and embryo. Prominent expression sites include the olfactory placode, the basal layer of the olfactory epithelium, the neuroepithelium of the developing retina, the germinal zone of the differentiated eye, regions of motoneuron development in the neural tube and periventricular regions of the brain. In embryo, expressed ubiquitously, but with decreasing intensity, from the one-cell through gastrula stages. At 36-48 hpf, mutants exhibit pericardial edema due to dysmorphic hearts that fail to loop and form and atrioventricular (AV) canal. Hearts show continues peristatic pumping rather than coordinated and sequential beating of atrial and ventricular chambers. Endocardial cells remain squamous and AV myocardial cell shape fail to occur.