Type I collagen is the most abundant and well characterized collagen in vertebrates. It forms 90% of the organic mass of bone and tendon and is the major collagen of skin, ligaments, cornea, and many interstitial connective tissues. The helical type I collagen molecule is a heterotrimer composed of two α 1 chains and one α 2 chain, which encoded by the COL1A1and COL1A2 genes and located on chromosome 17 and 7 respectively. (75)
The evidence for involvement of COL1A1 gene in pathogenesis of otosclerosis comes from research in a related disorder