DIFFERENTIAL DISTRIBUTION OF MESSENGER-RNA FOR THE ALPHA-SUBUNIT AND BETA-SUBUNIT OF CHORIONIC-GONADOTROPIN IN THE IMPLANTATION STAGE BLASTOCYST OF THE MARMOSET MONKEY

We studied the expression of mRNA encoding the alpha- and beta-subunit s of marmoset chorionic gonadotrophin (mCG) in implantation stage blas tocysts and in a trophoblastic cell line derived from such blastocysts . In this investigation in situ hybridization was carried out using di goxygenin-labelled riboprobes to localize the subunit transcripts. The trophoblastic cell line, known to secrete bioactive mCG, was used as a positive control. Marmoset uterine embryos were cultured to hatched blastocysts and following growth on Matrigel or plastic mere processed for in situ hybridization at developmental stages ranging from 13-15 days post-conception. In serial sections mCG-beta mRNA was detected ma inly in polar trophoblast. The mRNA for mCG-alpha was expressed more u niformly in polar and mural trophoblast. Transcripts for the beta-subu nit were riot expressed, or present as weak signals, in the inner cell mass (ICM) and endoderm. However, low levels of mRNA for mCG-alpha we re detected in the ICM and visceral endoderm. We have concluded that m RNA for mCG-beta was primarily localized to patches of syncytiotrophob last at the embryonic pole and sparsely distributed in mural trophobla st, while the transcripts for mCG-alpha were distributed more uniforml y in differentiating cytotrophoblast and syncytium, and at much lower levels ill ICM and early endoderm.