Circulating placental RNA in maternal plasma is associated with a preponderance of 5' mRNA fragments: implications for noninvasive prenatal diagnosis and monitoring.
BACKGROUND
The molecular characteristics of placental RNA circulating in maternal plasma are unknown. We investigated the integrity of circulating placental RNA in maternal plasma and tested the relevance of plasma RNA integrity for noninvasive prenatal diagnosis.


METHODS
Six different placental transcripts and mRNA of the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were quantified for the 5' and 3' regions in maternal plasma by 1-step real-time reverse transcription-PCR (RT-PCR) assays. This quantitative strategy was validated by 2-step RT-PCR and serial dilution experiments. The rates of detection by the 5' and 3' assays for the beta-subunit of human chorionic gonadotropin (beta hCG) were assessed in maternal plasma samples collected from different gestational periods.


RESULTS
For 5 of the 7 genes, the plasma mRNA concentrations measured by the 5' amplicons were significantly higher than those measured by the corresponding 3' amplicons. Every transcript under study demonstrated a higher rate of detection in the 5' assay than in the 3' assay in maternal plasma. In particular, the detection rate of beta hCG mRNA in maternal plasma was increased throughout gestation when the 5' assay was used.


CONCLUSIONS
Circulating placental RNA is associated with a preponderance of 5' mRNA fragments in maternal plasma. Apart from its intrinsic biological interest, this information could have important implications for the development of new assays targeting fetal RNA markers for noninvasive prenatal diagnosis and monitoring.
Wong
Blenda C K
BC
Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China.
Chiu
Rossa W K
RW
Tsui
Nancy B Y
NB
Chan
K C Allen
KC
Chan
Lin W
LW
Lau
Tze K
TK
Leung
Tse N
TN
Lo
Y M Dennis
YM
D006063:Chorionic Gonadotropin / Q000097:blood; D005260:Female; D020869:Gene Expression Profiling; D005820:Genetic Testing; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000097:blood* / Q000235:genetics; D006801:Humans; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D011296:Prenatal Diagnosis; D012313:RNA / Q000097:blood* / Q000235:genetics; D012333:RNA, Messenger / Q000097:blood* / Q000235:genetics; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity
D006063:Chorionic Gonadotropin; D012333:RNA, Messenger; D012313:RNA; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases