@entity10821 expression in embryonic XXXX chondrocytes treated with phorbol myristate acetate.

@entity5 @entity4515 @entity1359 @entity1573 @entity10821
Growth of embryonic @entity1573 sternal chondrocytes in the presence of @entity1359 ( @entity4515 ), a potent @entity5 promoter, resulted in a dramatic morphological change from spherical floating cells to adherent fibroblastic cells. This morphological change was accompanied by a quantitative switch from synthesis of cartilage-specific type II procollagen to type I procollagen. Type II procollagen mRNA levels decreased 10-fold in @entity4515 -treated cells. Activation of type I @entity10821 genes led to the accumulation of type I procollagen mRNA levels comparable to those of type II mRNA in these cells. However, only type I procollagen mRNA was translated. In addition to gene activation, unprocessed pro alpha 1(I) transcripts present at low levels in control chondrocytes were processed to mature mRNA species. Redifferentiation of @entity4515 -treated chondrocytes was possible if cells were removed from @entity4515 after the morphological change and cessation of type II procollagen synthesis but before detectable amounts of type I procollagen were synthesized. Production of type I @entity10821 thus marks a late phase of chondrocyte "dedifferentiation" from which reversion is no longer possible. Redifferentiated cell populations contained 24-fold more pro alpha 1(II) @entity10821 mRNA than pro alpha 1(I) @entity10821 mRNA, but the rates of procollagen synthesis were comparable. This suggests that the @entity4515 -mediated dedifferentiation of chondrocytes as well as their redifferentiation is under both transcriptional and posttranscriptional regulation.
