Six5 (homeobox protein SIX5), also known as SIX5, BOR2 or DMAHP (DM locus-associated homeodomain protein), is a transcription factor that is expressed in various structures of the adult eye. Localized to the cytoplasm in early development and to the nucleus in the later stages of development,Six5 is involved in regulation of organogenesis and in maintenance of retinal formation. Six5 is able to bind the 5'-TCA[AG][AG]TTNC-3' DNA sequence found in the myogenin and IGFBP5 promoters and, through this binding, can control transcription of the associated mRNA. Six5 is regulated via association with DACH1 (dachshund homolog 1) and is co-activated by the EYA (eyes absent) proteins. Defects in the gene encoding Six5 are the cause of branchiooto- renal syndrome type 2 (BOR2), an autosomal disorder characterized by hearing loss, a deep overbite and myopia. Two isoforms exist due to alternative splicing events.