The collagen alpha-2(I) chain (COL1A2) gene encodes the pro-alpha2 chain of type I collagen. Type I collagen is a fibrous structural protein that is widely present in most connective tissues, particularly in the extracellular matrix of bone, cornea, dermis, and tendons. In this model, the P2A-iCre element is knocked into the mouse Col1a2 gene at the TAA stop codon. Its specific expression is regulated by the mouse Col1a2 gene. When crossed with mice containing loxP sites, the offspring mice can undergo sequence recombination between loxP sites in fibroblast cells, mediated by the Cre recombinase.