Receptor for retinoic acid. Retinoic acid receptors bind as heterodimers to their target response elements in response to their ligands, all-trans or 9-cis retinoic acid, and regulate gene expression in various biological processes. The rar/rxr heterodimers bind to the retinoic acid response elements (RARE) composed of tandem 5'-AGGTCA-3' sites known as DR1-DR5 (By similarity). Heterodimer; with a rxr molecule. Binds DNA preferentially as a rar/rxr heterodimer. Isoforms differ in their N-terminal section. Expressed in embryos, tadpoles and various adult tissue such as kidney, testis, brain, liver, skeletal muscle and spleen. It is synthesized during oogenesis and persists during early cleavage. It accumulates at gastrulation (stage 10), peaks in quantity during neurulation (stage 17), then drops to a low level after stage 26. Isoform 1 is strongly expressed in branchial arches and to a lesser extent in the neural floor plate, but is not expressed neither in the pre-somitic mesoderm nor notochord. At gastrula stages 10-11, isoform 2 is mainly found in ectoderm and mesoderm with greater expression in the prospective dorsal side. At neurula stage, expressed anteriorly in the head mesoderm and in the archenteron roof. In early tadpole stage, expressed in head mesenchyme and in the tailbud. Composed of three domains: a modulating N-terminal domain, a DNA-binding domain and a C-terminal ligand-binding domain. Belongs to the nuclear hormone receptor family. NR1 subfamily.