Figure 4 - PLAC4 mRNA for fetal trisomy-21 detection.

(a) MS tracings of PLAC4 allelic ratio determination in placental and maternal plasma samples. Left panels, samples from a pregnant woman carrying a euploid fetus. Middle panels, samples from a pregnant woman carrying a trisomy 21 fetus with an extra A allele. Right panels, samples from a pregnant woman carrying a trisomy 21 fetus with an extra G allele. The x axis depicts the molecular weights of the detected extension products (shown as sharp peaks), whereas the y axis depicts the intensity in arbitrary units. The extension product of the A allele is shown as the first peak, whereas the extension product of the G allele is shown as the second peak. (b) RNA-SNP allelic ratios of PLAC4 in placentas and maternal plasma of euploid and trisomy-21 pregnancies. The ratios of the trisomy-21 samples segregated into two groups. Trisomy samples with an extra G allele showed a higher G/A ratio than the euploid group, whereas samples with an extra A allele showed a lower G/A ratio than the euploid group. The reference intervals, defined as the mean 1.96 s.d., are delineated by dashed lines. (c) Correlation between PLAC4 RNA-SNP allelic ratios in plasma and placenta. (d) Absolute PLAC4 mRNA concentrations in plasma of women carrying euploid and trisomy-21 fetuses.