Gene regulation during cartilage differentiation: temporal and spatial expression of link protein and cartilage matrix protein in the developing limb.

The temporal and spatial expression of link protein and cartilage matrix protein genes was defined during chondrogenesis in the developing chick embryonic wing bud, using RNA in situ hybridization. For comparison, the expression of genes encoding type II collagen and cartilage proteoglycan core protein was also examined. Link protein transcripts are first detected at stage 25 of Hamburger and Hamilton, together with proteoglycan core protein transcripts. Type II collagen transcripts were first detected as early as stage 23 whereas cartilage matrix protein transcripts could not be detected before stage 26. The results of the study indicate that the temporal expression of the genes for cartilage matrix protein and type II collagen are independent of each other and also independent of that for link protein and proteoglycan core protein.