AbstractTwo TGF-βs, TGF-β1 and 2, have previously been isolated from the mouse. Here we report the isolation of a murine TGF-β3 cDNA. RNAs extracted from 15-day-old mouse embryos and several mouse cell lines were reverse-transcribed. These cDNA mixtures were used as substrates for polymerase chain-reaction amplifications, using oligonucleotides designed on the basis of known human and chicken TGF-β3 sequences, including the initiation and stop codons. Several overlapping cDNAs containing either the amino-terminal domain or the carboxy-terminal domain, as well as the complete 1.2-kb coding region of the mouse TGF-β3 cDNA were obtained. The mouse TGF-β3 coding region is 1230 nucleotides long and codes for a 410 amino acid polypeptide very similar to its human counterpart. This cDNA hybridizes to a unique 3.5-kb RNA and is differentially expressed in various mouse tissues and at different embryonic stages.