Sex Determining Region Y Box Protein 21 (SOX21)

In the chick embryo, Sox21 promotes neuronal cellular differentiation by counteracting the activity of Sox1, Sox2, and Sox3, which maintain neural cells in an undifferentiated state.SOX21 knockout mice display hair loss beginning from postnatal day 11. New hair regrowth was initiated a few days later but was followed by renewed hair loss. Sox21 is also expressed in the hair shaft cuticle in humans and consequently variants of the Sox21 gene could be responsible for some hair loss conditions in humans. The partial SOX21 sequence encodes a deduced protein with an HMG box-like domain sharing 63% sequence identity with the SRY HMG box. Like the HMG box of SRY, the HMG box-like domain of SOX21 contains a putative nuclear localization signal.