Type IX collagen, a heterotrimer of αl(IX), α2(IX) and α3(IX) chains, is a cartilage-specific fibril-associated collagen. In the process of characterizing genomic clones for the mouse α2(IX) collagen gene four pairs of oligonucleotide primers designed for amplification of murine exon sequences were also utilized to construct cDNA clones for human α2(IX) collagen spanning > 90% of the coding region. The amino acid and nucleotide sequence identities between human and chick are 78% and 71%, respectively. Localization of the COL9A2 gene to human chromosome 1 was subsequently performed using a panel of DNAs from human/rodent somatic cell hybrids.
