The control of expression of type II collagen: relevance to cartilage disease

Cartilage is a unique tissue containing only one cell type, the chondrocyte, surrounded by an extensive extracellular matrix. One of the principal components of the cartilage matrix is type II collagen. The gene coding for type II collagen is relatively large and contains several distinct sequences that function to both up-regulate and down-regulate expression by interacting with chondrocyte transcription factors. Also, there appears to be regulation of collagen II expression by differential splicing of the collagen II mRNA to form different forms of the protein. Finally, the gene is a target for mutations that result in diseases of cartilage such as chondrodysplasias and some forms of osteoarthritis.