Transcription factor that is involved in the regulation of cell proliferation, apoptosis and embryonic development. Depending on context, functions as transcriptional repressor or activator. Plays an important role in the development of the inner ear, where it promotes hair cell proliferation and inhibits proliferation of neural progenitor cells (By similarity). 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. Ubiquitous during segmentation. Detected in otic vesicle and statoacoustic ganglion at later stages of development. At 24 hpf, detected in developing fast muscle throughout the trunk. Morpholino knockdown of the protein disrupts both skeletal muscle development in the trunk and cranial muscle development. Disrupts myogenesis by interfering with the proliferation of dermomyotomal cells expressing pax7. Belongs to the SIX/Sine oculis homeobox family. Zebrafish has two genes coding for six1 orthologs. This gene is called six1a by ZFIN, but has also been described as six1b (PubMed:18789916).