Placenta-derived fetal specific mRNA is more readily detectable in maternal plasma than in whole blood.
BACKGROUND
Placental mRNA was detected in maternal whole blood, raising the possibility of using maternal blood for noninvasive prenatal diagnosis. We investigated fetal mRNA detection in maternal whole blood and determined if it offered advantages over maternal plasma analysis.


METHODS
The concentrations of placental expressed genes, CSH1, KISS1, PLAC4 and PLAC1 in plasma and whole blood from healthy pregnant and non-pregnant individuals were compared by real-time quantitative reverse-transcriptase polymerase chain reaction analysis. Their fetal specificity was investigated by comparing the transcript concentrations in pre- and post-delivery samples and through SNP genotyping by matrix-assisted laser-desorption and ionization time-of-flight mass spectrometry. The gene expression profiles of pregnant and non-pregnant whole blood were investigated by microarray analysis. Upregulated genes in pregnant whole blood were selected for further quantitative analysis.


RESULTS
The concentrations of the four transcripts were significantly higher in third trimester maternal whole blood than corresponding plasma without significant correlations. KISS1, PLAC4 and PLAC1 were detected in non-pregnant whole blood but not plasma. The transcripts remained detectable in some postpartum whole blood samples. The PLAC4 mRNA in maternal plasma showed fetal genotype while that in corresponding whole blood indicated both fetal and maternal contributions. Microarray analysis revealed upregulation of genes involved in neutrophil functions in pregnant whole blood including DEFA4, CEACAM8, OLFM4, ORM1, MMP8 and MPO. Though possibly pregnancy-related, they were not pregnancy-specific as suggested by the lack of post-delivery reduction in concentrations.


CONCLUSIONS
Maternal plasma is preferred over maternal whole blood for placenta-derived fetal RNA detection. Most studied 'placental' mRNA molecules in maternal whole blood were of maternal origin and might be derived from processes such as 'illegitimate transcription'.
Heung
Macy M S
MM
Centre for Research into Circulating Fetal Nucleic Acids, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong Special Administrative Region, China.
Jin
Shengnan
S
Tsui
Nancy B Y
NB
Ding
Chunming
C
Leung
Tak Y
TY
Lau
Tze K
TK
Chiu
Rossa W K
RW
Lo
Y M Dennis
YM
D005260:Female; D005333:Fetus / Q000378:metabolism; D020869:Gene Expression Profiling; D005838:Genotype; D006801:Humans; D059648:Kisspeptins; D009035:Mothers; D010920:Placenta / Q000378:metabolism*; D010928:Placental Lactogen / Q000097:blood; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000097:blood; D011296:Prenatal Diagnosis; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D025521:Tumor Suppressor Proteins / Q000097:blood
C106628:KISS1 protein, human; D059648:Kisspeptins; C415583:PLAC1 protein, human; D011257:Pregnancy Proteins; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins; D010928:Placental Lactogen