Isolation of a mRNA preferentially expressed in synoviocytes from rheumatoid arthritis that is identical with lumican, which encodes a collagen binding Extracellular Matrix Protein

Rheumatoid arthritis (RA) is a complex disease including autoimmune disorder and resulting in inflammation. It also shows progressive proliferation of synoviocytes, and these synoviocytes destroys articular structure. In order to understand the mechanism of this abnormal proliferation of RA-originated synoviocytes in molecular level, we analyzed the gene expression profiles by using DNA chips that contain more than 10,000 genes. Comparing the expression profiles of normal and RA-originated synoviocytes, we found several genes that are highly expressed in RA-originated synoviocytes than normal synoviocytes. Among these genes, we focused on one hypothetical protein, cDNA of which contains one reading frame in its DNA fragment, indicating that this fragment is a part of large mRNA structure. The expression of this gene in RA-originated synoviocytes is about three times higher than that in normal synoviocytes by DNA chip analysis. After cDNA cloning of this mRNA, we found that the gene is identical with lumican, which encodes a collagen binding, extracellular matrix protein. This mRNA was widely distributed in many tissues but its alternatively spliced forms are differently expressed in various tissues.