Expression of transforming growth factor alpha during development.

Transforming growth factors (TGFs) are polypeptides that are produced by transformed and tumour cells, and that can confer phenotypic properties associated with transformation on normal cells in culture. One of these growth-regulating molecules, transforming growth factor alpha (TGF-alpha), is a 50 amino acid polypeptide that is related to epidermal growth factor (EGF) and binds to the EGF receptor. Previous studies have shown that TGF-alpha is expressed during rodent embryogenesis between 7 and 14 days gestation. To investigate the cellular sites of TGF-alpha mRNA expression during development, we have performed Northern analyses and in situ hybridization histochemistry on the conceptus and maternal tissues at various gestational ages. Contrary to previous reports, both Northern analyses and in situ hybridization histochemistry indicate that TGF-alpha mRNA is predominantly expressed in the maternal decidua and not in the embryo. Decidual expression is induced following implantation, peaks at day 8, and declines through day 15 when the decidua is being resorbed. In situ hybridization revealed that expression of TGF-alpha mRNA is highest in the region of decidua adjacent to the embryo and is low or nondetectable in the uterus, placenta, and embryo. In addition, we could not detect TGF-alpha mRNA expression in other maternal tissues, indicating that the induction of TGF-alpha transcripts in the decidua is tissue specific, and not a pleiotropic response to changes in hormonal milieu that occur during pregnancy. The developmentally regulated expression of TGF-alpha mRNA in the decidua, together with the presence of EGF receptors in this tissue, suggests that this peptide may stimulate mitosis and angiogenesis locally by an autocrine mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)