Expression of transforming growth factor β2 during the differentiation of murine embryonal carcinoma and embryonic stem cells

Abstract

Transforming growth factor β 2 (TGF β 2) mRNA expression was studied by Northern blot analysis in a range of feeder-independent murine embryonal carcinoma (EC) cells and in feeder-dependent EC and embryonic stem (ES) cells. TGF β 2 transcripts were not detected in any undifferentiated cells including P19, F9, PC13, C1003, PSA-1, P10, and ES. Following induction of differentiation, however, TGF β 2 became expressed, independently of the cell type formed. Retinoic acid (RA) addition and/or deprivation of the differentiation inhibiting activity of feeder cells resulted in the appearance of TGF β 2 transcripts within 2 days. These kinetics correlated entirely with the first appearance of the protein; an anti-peptide antibody specifically recognizing TGF β 2 did not stain P19 EC cells by immunofluorescence but 2–3 days after RA addition, a significant proportion of the population was strongly labeled. In addition, primitive endoderm cells emerging from the inner cell mass of substrate attached blastocysts stained brightly with anti-TGF β 2, while the undifferentiated inner cell mass cells did not. Although all trophectoderm cells at the mid-blastocyst stage were stained, few had detectable levels of TGF β 2 after plating on a substrate. Neither TGF β 1 nor TGF β 2 affect growth of EC cells, but a range of differentiated derivatives were all inhibited, with TGF β 2 being marginally more effective than TGF β 1 at the same concentration.