The DDR1 gene comprises 17 exons and spans 12 kb of the genomic sequence on chromosome 6 (from position 30851861 bp to 30867933 bp in the positive strand orientation).

The 3840-bp mRNA is transcribed in a centromeric to telomeric orientation. Alternative splicing can occur, and 5 named isoforms (DDR1a-e) are recognised.

No pseudogene has been described.

DDR1 belongs to the DDRs subfamily of tyrosine kinase receptors. This subfamily is composed of only two members, DDR1 and DDR2, and it is distinguished by an extracellular domain that is homologous to the carbohydrate-binding lectin discoidin-I in Dictyostelium discoideum. The Discoidin domain is essential for the ability of DDRs to bind ligands. To-date, collagen is the only unique DDR1 ligand that has been identified. Five isoforms of DDR1 that are generated by alternative splicing have been described. The longest DDR1 transcript codes for the full-length receptor (DDR1c isoform) and is composed of 919 amino acids. DDR1a and DDR1b isoforms lack 37 amino acids in the juxtamembrane domain or 6 amino acids in the kinase domain. DDR1d and DDR1e isoforms are C-terminally truncated receptors. DDR1d lacks exons 11 and 12 causing a frame-shift mutation that generates a stop codon and premature termination of transcription. Finally, DDR1e lacks exons 11 and 12 as well as the first half of exon 10 (Alves et al., 1995).

DDR1 is ubiquitously expressed in a variety of epithelial tissues (Alves et al., 1995; Curat and Vogel, 2002; Ferri et al., 2004; Hou et al., 2001; Mohan et al., 2001; Sakamoto et al., 2001; Tanaka et al., 1998). DDR1 is also expressed in endothelial blood capillary cells and oligodendrocytes in the human brain (Franco-Pons et al., 2009; Roig et al., 2010). DDR1 is significantly overexpressed in several human cancers (Barker et al., 1995; Colas et al., 2011; Ford et al., 2007; Hajdu et al., 2010; Heinzelmann-Schwarz et al., 2004; Laval et al., 1994; Nemoto et al., 1997; Park et al., 2007; Tun et al., 2011; Weiner et al., 1996; Weiner et al., 2000; Yamanaka et al., 2006; Yoshida et al., 2007) and carcinoma cell lines (Alves et al., 1995; Gu et al., 2011; Park et al., 2007; Sakuma et al., 1996).

Transmembrane.

Receptor tyrosine kinases are key components of several signal transduction pathways. These kinases control multiple cellular processes, including motility, proliferation, differentiation, metabolism and survival.
DDR1 is actively involved in tumorigenesis and promotes the proliferation of neoplasic cells. The interaction of DDR1 and Notch1 displays a prosurvival effect (Kim et al., 2011). DDR1 participates in the collective migration of cancer cells by coordinating the cell polarity regulators Par3 and Par6 (Hidalgo-Carcedo et al., 2011).

- P. troglodytes, discoidin domain receptor tyrosine kinase 1, DDR1
- C. lupus, discoidin domain receptor tyrosine kinase 1, DDR1
- M. musculus, discoidin domain receptor family member 1, Ddr1
- R. norvegicus, discoidin domain receptor tyrosine kinase 1

Few somatic mutations have been described. Four mutations (G1486T, A496S, CC2469/2470TT, R824W) have been identified in a cohort of 26 primary lung neoplasms (Davies et al., 2005). One somatic mutation (A803V) was found in 4 acute myeloid leukaemia patients (Tomasson et al., 2008).