Figure 1.

Schematic diagram of the subunits of collagen VI. All the 6 chains and their encoding genes are presented. The molecular structures of collagen VI subunits are similar: a short collagenous triple-helical domain and three von Willebrand factor type A (vWF-A) domains (N1, C1, and C2). Nine additional vWF-A domains are found in the N-terminal domain (N2–N10) and 3 special domains are found in the C-terminal domain (C3–C5) in the collagen alpha-3 (VI) chain. The area marked by arrows shows the collagenous domain and the cleaved C5 domain fragment endotrophin. In humans, the COL6A4 gene is disrupted by a chromosome break to create two pseudogenes. In addition, the N2–N10 vWF-A domains are each encoded by a single exon accordingly from exon 11 to exon 3 (E11–E3), and the domains undergo alternative splicing are marked orange. Due to the alternative splicing of COL6A3 at the pre-mRNA level, the N3, N5, N7, N9 and N10 vWF-A domains of the collagen alpha-3 (VI) chain are either present or absent in the final chain. The tumor-specific alternative splicing of exons 6, 4, and 3 (E6, E4, and E3) are also showed in the Figure in Red marks. This figure was modified with permission from Cescon M, Gattazzo F, Chen P, Bonaldo P. Collagen VI at a glance. J Cell Sci. 2015;128(19):3525–3531. doi:10.1242/jcs.169748. Copyright 2015, The Company of Biologists Ltd.¹⁰⁰

Abbreviations: TH, triple helical; vWF-A, von Willebrand factor type A; E3, exon 3; E4, exon 4; E5, exon 5; E6, exon 6; E7, exon 7; E8, exon 8; E9, exon 9; E10, exon 10; E11, exon 11.