TCF7 gene structure. TCF7 gene contains multiple exons. Different splicing may transcribe to variants of mRNAs, and translates to different protein isoforms. Exon Ia, Ib, IVa, and IX are alternative exons. There exits two promoters as shown in the figure. The first promoter can generate mRNAs encoding a full-length activating form of protein isoforms which contains the β-catenin binding domain, while the second promoter cannot and thus produce the truncated dominant-negative isoforms. Therefore, two different groups of TCF7 isoforms function differently.