GENE-EXPRESSION OF HUMAN PREGNANCY-ASSOCIATED PLASMA-PROTEIN-A IN PLACENTA FROM TRISOMIC PREGNANCIES

Placental pregnancy-associated plasma protein-A (PAPP-A) mRNA expressi on, placental PAPP-A protein concentration and maternal serum levels o f PAPP-A were examined in pregnancies affected by trisomy 21 (n=8), tr isomy 18 (n=7) and 15 normal controls at 12-15 weeks of gestation. The maternal serum concentration of PAPP-A in the trisomic group of pregn ancies was significantly lower than in the normal controls. However th ere were no significant differences between the three groups in PAPP-A mRNA expression or PAPP-A protein concentration in the placental tiss ues. There was no significant association between the level of placent al mRNA and either placental protein or maternal serum PAPP-A concentr ations in the normal or trisomic pregnancies. There was however a sign ificant association between placental protein and maternal serum PAPP- A concentrations in the normal and trisomy 21 pregnancies but not in t hose affected by trisomy 18. These findings suggest that the decrease in maternal serum PAPP-A in trisomic pregnancies is due to alterations in post-translational events such as protein stability, alterations i n the release mechanism of the protein, impaired protein transport acr oss the placenta or modified serum stability of PAPP-A. (C) 1996 W. B. Saunders Company Ltd