Objective: The purpose of this research was to attempt a preliminary study of noninvasive prenatal diagnosis of Down syndrome in Southwest Chinese gravidas by using the plasma placental RNA allelic ratio.
Methods: The genotypes of the single-nucleotide polymorphisms (SNPs) located in the transcribed regions of the gene PLAC4 were detected in population samples collected in Southwest China by using polymerase chain reaction-restriction fragment length polymorphism, and SNPs with a higher heterozygosity were selected. Mass spectrometer analysis was adopted, and cases with the heterozygous SNPs on PLAC4 mRNA in maternal plasma were selected from 29 pregnancies with a euploid fetus and from 21 pregnancies with a trisomy-21 fetus, and then their RNA-SNP allelic ratios were further determined for noninvasive prenatal diagnosis of Down syndrome.
Results: Of all 50 singleton pregnancies, 37 gravidas were found with at least one heterozygous SNP on PLAC4 mRNA in maternal plasma. Among them, 13 pregnancies with a trisomy-21 fetus were detected by the analysis of the RNA-SNP allelic ratio.
Conclusion: The plasma placental RNA allelic ratio can be used for noninvasive prenatal diagnosis of Down syndrome, if SNPs on PLAC4 mRNA in maternal plasma are heterozygous.