Establishes the cardiac repolarization gradient by its repressive actions on the KCND2 potassium-channel gene. Required for retinal cone bipolar cell differentiation. May regulate contrast adaptation in the retina and control specific aspects of visual function in circuits of the mammalian retina. Involved in craniofacial and gonadal development (By similarity). Modulates the migration of progenitor cell populations in branchial arches and gonads by repressing CXCL12. Not expressed in the developing metanephric kidney or adult kidney. In 9.5 dpc embryos, expressed in the rhombencephalon, metencephalon, and in the cephalic mesoderm surround the optic vesicle. By 12.5 dpc, expression continues in the mesenchyme and also begins in subsets of cells in the neuroretina, becoming expressed in the retinal inner neuroblast layers by 16.5 dpc. Expressed in developing bipolar cells during retinal development starting at postnatal day 5, and expressed in a subset of cone bipolar cells in the mature retina. Also expressed along the spinal cord, in the ventricular layer, in motor neurons and in the proximal limb buds during embryonic development. Expressed in the developing heart in the endocardium that lines the heart chambers. Disruption causes increased KCND2 potassium-channel expression in endocardial myocardium leading to abolition of the cardiac repolarization gradient, a selective increase of the major cardiac repolarization current, I(to,f), and increased susceptibility to arrhythmias. Belongs to the TALE/IRO homeobox family.