CLONING OF A MOUSE SMOOTHENED CDNA AND EXPRESSION PATTERNS OF HEDGEHOG SIGNALING MOLECULES DURING CHONDROGENESIS AND CARTILAGE DIFFERENTIATION IN CLONAL MOUSE EC CELLS, ATDC5

Hedgehog (hh) family proteins appear to use the conserved targets in t heir signalling pathway including Patched (Ptc), Smoothened (Smo), and Gli. Although Indian hedgehog (Ihh) plays an important role in endoch ondral bone formation, the involvement of hh signalling molecules in s keletogenesis is unknown. We cloned a mouse (m) Smo cDNA and studied t he expression patterns of Ihh, Ptc, Smo, and Gli mRNAs in mouse chondr ogenic EC cells, ATDC5. The deduced amino acid sequence of mSmo consis ted of 793 amino acids and was 98 and 93% homologous to the rat (r) Sm o and human (h) Smo, respectively. In ATDC5 cells, the expression of I hh mRNA paralleled that of type X collagen mRNA, Smo, Ptc, and Gli mRN As were constitutively expressed throughout chondrogenesis and the sub sequent cartilage differentiation processes except for the transient d ecrease in Ptc mRNA at the cellular condensation stage. Our data sugge st that hh signalling molecules may be involved in chondrogenesis and cartilage differentiation in ATDC5 cells. (C) 1997 Academic Press.