Transcription factor 7-like 1 (TCF7L1; also HMG box transcription factor 3, TCF-3) is a 63kD member of the TCF/LEF family of proteins. Human TCF7L1 is 588 aa in length and contains one HMG box DNA-binding domain (aa346-414). Human TCF7L1 shares 95% aa sequence identity with mouse TCF7L1. TCF7L1 is expressed in hair follicles and skin keratinocytes, and at lower levels in stomach epithelium. Functionally, it participates in the Wnt signaling pathway. TCF7L1 binds to DNA and acts as a repressor in the absence of CTNNB1, and as an activator in its presence. TCF7L1 is also necessary for the terminal differentiation of epidermal cells, the formation of keratohyalin granules and the development of the barrier function of the epidermis.