Changes in mRNA expression of ovine transforming growth factor-B isoforms in late estrous cycle and early gestational endometrium and early gestation embryonic membranes

Utilizing cDNA clones of bovine transforming growth factor-61, 62 and 63, (TGF-β) three DNA probes were constructed so as to be isotype specific. Total RNA was isolated from ovine endometrium from days 13 and 16 of the estrous cycle and days 13, 16, 23, 27 and 30 of gestation. RNA was also isolated from day 13 and 16 expanding blastocysts and days 23, 27 and 30 chorion and allantoic membranes. Using Northern blot methodology the sizes of each TGF-β isoforms transcripts was determined. In both embryonic and endometrial tissues the transcript sizes were similar for each isoform. Transcript sizes for TGF-β1 was 2.6 kb in length, the TGF-β2 five transcripts lengths of 6.2, 5.2, 4.7, 4.2 and 2.7 kb and TGF-β3 transcript of 3.8 kb in length. Using slot blot methodology, changes in relative mRNA expression levels of each isoform were determined in both endometrial and embryonic tissues. All three TGF-β isoforms were found in the endometrium at all days examined, regardless of status. In embryonic tissues only levels of TGF-β1 and β2 were described, since TGF-β3 levels were at or below detection limits. TGF-β1 was primarily expressed by the developing allantois, with both placental membranes expressing TGF-β2. Temporal changes in both maternal and conceptus TGF-β expression corresponds to major morphological changes in the developing placenta, suggesting a link to placental development, as well as endometrial modifications during the late estrous cycle.