TCF1 also known as TCF7 is a member of the T-cell factor/lymphoid enhancer-binding factor family of high mobility group (HMG) box transcriptional activators. TCF1 plays a crucial role in lymphoid cell development as a DNA-binding transcriptional activator. TCF1 is activated through the Wnt signaling pathway, which is essential for regulating gene expression during cell differentiation and proliferation. TCF1 contains a high mobility group (HMG) box that facilitates binding to DNA, allowing regulation of Wnt target genes. TCF1 exists in several splice variants, including TCF1A, which share a conserved amino terminus but differ in carboxy terminal sequences, potentially influencing functional roles in various cellular contexts.