Figure 1. Structure of the human TFPI Gene.

The TFPI gene spans 90 kb and contains 10 exons (vertical boxes) and 9 introns that encode for three isoforms. Exons are labeled numerically (top), introns alphabetically (bottom). Translated exons encoding TFPIα are filled in blue. Alternatively spliced exons leading to the generation of TFPIδ and TFPIβ are filled in magenta and red, respectively. Exons 1 and 2 encode 5′ untranslated (5′UT) sequences with alternative splicing resulting in the absence of exon 2 in some messages. Exon 3 encodes the signal peptide and amino terminal peptide (SP+NT). Exons 4, 6 and 9 encode Kunitz domains 1 (K1), 2 (K2) and 3 (K3), respectively and intervening peptide sequences that link the Kunitz domains are encoded by exons 5 (IP1) and 7 (IP2). A run-on of exon 6 into intron F (magenta) encodes the short TFPIδ variant carboxyl terminus (δCT). The TFPIβ carboxy-terminal peptide (βCT) is encoded by exon 8 (red) and splicing of exon 7 to exon 8 occurs to generate the TFPIβ message. In the TFPIα message exon 9 is directly spliced to exon 7 (K3) and to exon 10 (αCT), thereby encoding the Kunitz-3 and carboxyterminus of the TFPIα protein.