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Comparison of the sequence of the N-terminal 30 amino acids of cartilage-inducing factor-A (CIF-A) from bovine demineralized bone with the corresponding sequence of human transforming growth factor-beta (TGF-beta) revealed 100% identity. Furthermore, CIF-A stimulated normal rat kidney fibroblasts to become anchorage-independent and form colonies in soft agar (in the presence of epidermal growth factor) in a manner similar to TGF-beta. Similarly, TGF-beta from human platelets induced rat muscle mesenchymal cells to differentiate and synthesize cartilage-specific macromolecules in a manner equivalent to CIF-A. These data show that CIF-A and TGF-beta are closely related or identical molecules and that these factors may be involved in cell differentiation including cartilage formation as the first step in endochondral bone formation.
Seyedin et al. (Thu,) studied this question.