Transcription factor that is involved in the regulation of cell proliferation, apoptosis and embryonic development. Depending on context, functions as transcriptional repressor or activator. Transcriptional activation is enhanced by eya1 (in vitro). Plays an important role in the development of the inner ear, where it promotes hair cell proliferation and inhibits proliferation of neural progenitor cells. Required for normal myogenesis. Plays a role in the development of fast muscle fibers throughout the body, as well as the development of craniofacial muscles. Required for normal expression of myod1 and myog during myogenesis. Interacts with eya1. First detected at mid-gastrulation. After the onset of segmentation, detected in cranial placode. At later stages of development, detected in the olfactory, otic, and lateral line placodes, in the developing inner ear and in neuromasts. After 48 hpf, no longer detected in the inner ear, but continues to be expressed in lateral line neuromasts. In addition, detected in the pituitary, branchial arches, somites, pectoral fin, ventral abdomen muscle, and the cranial muscles of the eye and lower jaw. Detected in developing fast muscle. Morpholino knockdown of the protein increases both cell proliferation and apoptosis in the otocyst. Increases proliferation of neuronal cells and decreases the number of cells destined to form hair cells. Disrupts myogenesis by interfering with the proliferation of dermomyotomal cells expressing pax7 and loss of myog expression. Belongs to the SIX/Sine oculis homeobox family. Zebrafish has two genes coding for six1 orthologs. This gene is called six1b by ZFIN and in PubMed:23444384, but has also been described as six1 (PubMed:17035528) and as six1a (PubMed:15254912, PubMed:18789916, PubMed:19409884).