TWO CARTILAGE INDUCING FACTORS (CIF), WHICH INDUCE THE DIFFERENTIATION OF MESENCHYMAL CELLS INTO CHONDROBLASTS IN VITRO, HAVE BEEN ISOLATED FROM BOVINE DEMINERALIZED BONE (SEYEDIN ET AL.

TWO CARTILAGE INDUCING FACTORS (CIF), WHICH INDUCE THE DIFFERENTIATION OF MESENCHYMAL CELLS INTO CHONDROBLASTS IN VITRO, HAVE BEEN ISOLATED FROM BOVINE DEMINERALIZED BONE (SEYEDIN ET AL. PROC. NATL. ACAD. SCI. 1985). THE INDUCED CELLS SYNTHESIZE DIFFERENTIATED CHONDROCYTE MARKERS SUCH AS CARTILAGE-SPECIFIC PROTEOGLYCANS AND TYPE II COLLAGEN. INDUCTION OF CHONDROGENESIS IN RESPONSE TO CIF IS EXPECTED TO BE MEDIATED THROUGH THE FINDING OF THE CIF TO A SPECIFIC PLASMA MEMBRANE RECEPTOR FOLLOWED BY ENDOCYTOSIS OF THE CIF-RECEPTOR COMPLEX, AS IS THE CASE WITH SEVERALPOLYPEPTIDE HORMONES AND GROWTH FACTORS.THIS PROJECT IS DIRECTED TOWARD IDENTIFICATION, PURIFICATION, AND CHARACTERIZATION OF THE RECEPTOR FOR CIF. PURIFICATION AND CHARACTERIZATION OF THE CIF RECEPTOR IS ESSENTIAL TO UNDERSTAND THE MECHANISM UNDERLYING CARTILAGE INDUCTION AND DIFFERENTIATION. THE FIRST PHASE OF THIS RESEARCH WOULD INVOLVE IDENTIFICATION AND INITIAL CHARACTERIZATION OF THE RECEPTOR FOR CIF EMPLOYING 125 I-CIF AS A PROBE. PHASE II WOULD BE DIRECTED TOWARD PURIFICATION AND FURTHER CHARACTERIZATION OF CIF RECEPTOR.