SIX1 (D5S2S) Rabbit mAb #16960

Sine oculis homeobox (SIX) proteins belong to a family of evolutionarily conserved transcription factors discovered in Drosophila mutant screens for embryonic eye development genes (1-3). The prototypical family member (sine oculis, so) was named for eyeless embryos carrying mutations in a gene highly conserved among vertebrates, including humans (SIX1) (4). A total of six family members (SIX1-6) have been identified in vertebrates. Each SIX protein contains a homeobox nucleic acid recognition domain (HD) with a DNA-binding helix-turn-helix motif and an adjacent SIX domain, which may be involved in regulating protein-protein interactions (5). In addition to their critical functions during embryonic organogenesis, research studies suggest that SIX proteins play additional roles in postnatal cell cycle regulation, with potentially important implications in tumorigenesis (6,7).
In contrast to the Drosophila ortholog, the vertebrate SIX1 gene product does not play a critical role in embryonic eye development. Vertebrate SIX1 is required for development of mesoderm- and neural crest-derived lineages, and male reproductive tissues (8-10). SIX1 has also been shown to regulate transcription of MyoD in adult muscle progenitor cells during postnatal muscle development (11). A mechanistic role for SIX1 in cell cycle regulation is supported by research studies showing increased SIX1 expression in various cancer subtypes, including breast, ovarian, and hepatocellular carcinoma (6,12,13).