Gas6, a new regulator of chondrogenic differentiation from mesenchymal cells.

The mesenchymal cell line C3H10T1/2 can be preferentially induced toward chondrogenesis by culturing as a micromass in the presence of bone morphogenetic protein 2. To screen new regulator genes for chondrogenic differentiation, we performed differential display polymerase chain reaction and identified growth arrest-specific 6 (Gas6) as a gene that was clearly downregulated by this induction of chondrogenic differentiation. Blockage of Gas6 mRNA expression by siRNA remarkably enhanced the chondrogenic differentiation, while stimulation with recombinant Gas6 inhibited the mRNA expressions of type II collagen (Col2a1) and aggrecan. Gas6 signaling activated the phosphorylation of ERK1/2, SAPK/JNK, and Akt, but not p38 MAPK. These results suggest that Gas6 negatively regulates chondrogenic differentiation, at least through the MAPK pathway.