Transforming growth factor beta4 (TGF-beta4) is unique to avian species, though its roles in vivo have not yet been well established. In this paper we describe the expression and partial characterization of recombinant chicken TGF-beta4. By using a GC-rich PCR system in a modified 5'RACE methodology we generated the 5'-end of cDNA sequence encoding the TGF-beta4 precursor, which was in-frame cloned into pcDNA3.1/V5-His-TOPO and transfected into the Chinese hamster ovary cell line (CHO-K1). A cell line stably expressing TGF-beta4 precursor protein was established from CHO-K1 cells. Acid-activated mature TGF-beta4 inhibited the growth of mink lung epithelial (Mv1Lu) cell line. TGF-beta4 also stimulated the expression of type 1 procollagen and enhanced heat shock protein 47 (Hsp47) expression in chicken tendon fibroblasts. Hsp47 expression by TGFbeta4 is likely regulated through activation of heat shock transcription factor 1 (HSF1). Because the presence of TGF-beta1 has not been documented in avian cells and our data show that TGF-beta4 elicits biological activities in chicken tendon cells, which closely parallel that of TGF-beta1, we propose that TGF-beta4 plays roles in avian species similar to what TGF-beta1 plays in mammalian species. (C) 2003 Elsevier Science (USA). All rights reserved.