AbstractUsing a simian transforming growth factor-β2 (TGF-β2) cDNA probe, we have isolated chicken cDNA clones for TGF-β2 from a chicken embryo chondrocyte cDNA library. The predicted precursor protein of chicken TGF-β2 is 412 amino acids long, two amino acids shorter than the human form to which it shows 90% identity. Cleavage of the chicken TGF-β2 precursor at a pentabasic Arg-Arg-Lys-Lys-Arg site would produce a 112-amino acid processed peptide differing by only one amino acid from the human TGF-β2 peptide. In contrast to TGF-β3 and 4 mRNAs, TGF-β2 mRNA is expressed in both cultured and non-cultured chicken embryo chondrocytes and at higher levels in chicken embryo fibroblasts. In chondrocytes and fibroblasts, the 3.9- and 4.3-kb TGF-β2 mRNAs are both expressed at higher levels than the 8-kb TGF-β2 mRNA; however, in developing chicken embryos, the level of expression of the 8-kb mRNA is higher than that of the 3.9- and 4.3-kb mRNAs.