cDNA probes and antibodies for TGF-βs 1, 2, 3, and 4 were used to study the expression of these different TGF-β isoforms in cultured chicken embryo chondrocytes and cardiac myocytes, as well as in developing cartilage and heart tissues. TGF-βs 2, 3, and 4 mRNAs, but not TGF-β1 mRNA, were detected in cultured chondrocytes and myocytes. Expression of TGF-βs 2 and 4 mRNAs increased with age, while expression of TGF-β3 mRNA was independent of age in chondrocytes cultured from 12- to 17-day-old embryos. In contrast, expression of TGF-βs 2, 3, and 4 mRNAs was constitutive in myocytes cultured from 7- to 9-day-old embryonic hearts; expression of TGF-βs 3 and 4 mRNAs increased, while expression of TGF-β2 mRNA remained unchanged in myocytes from 10-day-old embryos. Immunoprecipitation studies demonstrated expression of TGF-β in both the conditioned media and the cell lysates of metabolically labeled chondrocyte and myocyte cell cultures. Immunohistochemical staining of cultured chondrocytes and myocytes and of cartilage and heart tissues of developing chicken embryos with antibodies specific for each TGF-β isoform showed immunoreactive TGF-βs 1, 2, 3, and 4. Our results demonstrate coordinate expression of these four TGF-β isoforms in chicken embryo chondrocytes and myocytes, both in vitro and in vivo, with expression of TGF-βs 2, 3, and 4 mRNA and protein more prominent than that of TGF-β1. © 1991.