HGNC Approved Gene Symbol: COL22A1
Cytogenetic location: 8q24.23-q24.3 Genomic coordinates (GRCh38) : 8:138,588,235-138,914,041 (from NCBI)
COL22A1, a member of the FACIT (fibrillar-associated collagens with interrupted triple helices) subgroup of the collagen protein family, specifically localizes to tissue junctions (Koch et al., 2004).
By EST database searching, Koch et al. (2004) identified a sequence with homology to the C-terminal amino acid sequence of type XII collagen (COL12A1; 120320). Using PCR-based strategies, they isolated the full-length cDNA of a novel collagen, designated COL22A1, from placenta and hip cartilage/bone cDNA libraries. The deduced 1,626-amino acid protein contains a putative 27-amino acid signal peptide. It has the typical structure of a FACIT collagen, with an N-terminal globular domain and a short C-terminal collagenous stretch. The N terminus has a VWA (von Willebrand factor A-like) domain, followed by a TSPN (N-terminal thrombospondin-like domain) containing N-glycosylation sites. The C-terminal 105 amino acids contain interruptions in Gly-X-Y triplets followed by 2 cysteine residues. It shares the greatest overall homology with COL21A1 (610002), but its VWA domain also has similarity to the VWA domains of COL12A1 and matrilin-1 (MATN1; 115437). Northern blot analysis of human tisuses detected a 6.4-kb transcript in skeletal muscle and heart. RT-PCR on mouse tissues revealed additional signals in cartilage, skin and keratinocytes, and eye. In situ hybridization detected mouse Col22a1 mRNA exclusively in muscle cells at the muscle attachment sites to tendon elements and ribs. Immunofluorescence studies demonstrated that mouse Col22a1 protein distribution is specific to tissue junctions, including the myotendinous junction in skeletal and heart muscle, the articular cartilage-synovial fluid junctions, and the border between the anagen hair follicle and the dermis in skin. Immunoelectron microscopy localized Col22a1 to basement membranes outlining the myotendinous junction.
Using cell adhesion assays, Koch et al. (2004) demonstrated that COL22A1 acts as a cell adhesion ligand for lung fibroblasts expressing alpha-1/beta-1 and alpha-2/beta-1 integrins, and for keratinocytes expressing alpha-2/beta-1 integrins (Koch et al., 2004).
Koch et al. (2004) determined that the COL22A1 gene contains 66 exons and spans 326 kb. The signal peptide coding sequence is located in the second exon.
By genomic sequence analysis, Koch et al. (2004) mapped the COL22A1 gene to chromosome 8q24.2 and the mouse homolog to chromosome 15D2-D3.
Koch, M., Schulze, J., Hansen, U., Ashwodt, T., Keene, D. R., Brunken, W. J., Burgeson, R. E., Bruckner, P., Bruckner-Tuderman, L. A novel marker of tissue junctions, collagen XXII. J. Biol. Chem. 279: 22514-22521, 2004. [PubMed: 15016833] [Full Text: https://doi.org/10.1074/jbc.M400536200]