Acts partially redundantly with other irx members in neural patterning. Required for formation of the posterior forebrain, midbrain, hindbrain, and to a lesser extent, spinal cord. Acts early in neural plate development to induce expression of some but not all proneural genes, and specify a neural precursor state. Also up-regulates repressors that prevent neuronal differentiation. Patterns the neuroectoderm in both the anterior/posterior and dorsal/ventral axes. Acts primarily as a transcriptional repressor during neural development, and binds to the bmp4 promoter to repress gene expression and thus mediate down-regulation of bmp4 by wnt signaling. Controls multiple processes through bmp4-repression including neural plate development, neural crest specification and Spemann organizer development. Involved in the specification of the preplacodal field at the anterior border of the neural plate. Regulates the genetic cascade of interactions that are necessary for positioning the isthmus organizer and the formation of the midbrain-hindbrain boundary. Required during at least two stages of pronephros kidney development; during neurula stages, maintains transcription of key renal genes to define the size and identity of the pronephric anlage, probably in part through regulation of bmp-signaling. Subsequently required for proper formation of the intermediate tubule segment of the pronephros. Acts principally as a transcriptional activator during pronephros development. Expressed early in neural differentiation in the neural plate, and expression continues in the neural tube after neural fold closure. Expressed in the presumptive midbrain territory. Also expressed in the prospective neural crest and the preplacodal field, anterior to the neural plate. Strongly expressed in the profundal placode and weakly expressed in the trigeminal placode. Also expressed in the mesoderm in the Spemann organizer from the start of gastrulation, and subsequently in its derivatives; namely in the notochord as well as in the somites of stage 25 embryos, and the somites and notochord of tailbud embryos. Also expressed in specific and overlapping dynamic patterns with irx2 and irx3 during pronephric kidney development. Renal expression begins in the dorsal region of the pronephric anlage at mid neurula stage and continues to at least tailbud stages where expression is confined to the intermediate tubule segment IT1. Renal expression is maintained at tadpole stages. By wnt signaling. Mutually antagonizes bmp4 signaling. Inhibited in the neural plate by foxd5. The anterior limit of expression at the future border between the prethalamus and thalamus is defined by mutual repression with the anterior repressor fezf2, and also by arx. Induced by retinoic acid (RA) during kidney development. Belongs to the TALE/IRO homeobox family. Although PubMed:17875669 show that irx1 is dispensable for pronephric kidney development, PubMed:18715948 show that irx1 is required for formation of the pronephros.