Fig. 4.

Schematic illustration of TCF4 genomic sequence encompassing CTG18.1, defined protein coding TCF4 isoforms, and characterized TCF4 functional domains. A. Genomic sequence surrounding the CTG18.1 repeat element (red) and adjacent CTC repeat (blue). Intronic sequence surrounding the repeat is shown in lowercase black lettering. Exonic sequence is represented by uppercase letters. B. A schematic of the canonical TCF4 transcript (ENST00000354452.8; NM_001083962.2) encoding Isoform B (ENSP00000346440.3). Arrowhead shows the relative position of the SNP rs613872. Sequence is presented in a 5′ to 3′ orientation. C. A schematic representation of all characterized, protein coding, TCF4 transcripts reported in Ensembl. Transcripts that contain or are in close proximity to the CTG18.1 repeat (red dotted box) are grouped and colored in black. Those transcripts which do not encompass the repeat are colored grey. The transcripts encoding isoform A (TCF4-204 – red) and Isoform B (TCF4-201 - blue) are labelled. Colored boxes denote exons which code for specific TCF4 functional domains. D. Schematic of TCF4 protein functional domains characterized within isoform A and isoform B. Activation domain 1 (AD1) and activation domain 2 (AD2) are represented in blue, whereas the nuclear localization signal (NLS) is in red. Repressor regions of the protein are represented with R. The basic helix-loop-helix (bHLH) domain and the C domain are highlighted in light green and dark green, respectively.