High-throughput mRNA-seq atlas of human placenta at first and third trimester, all live births
Human placenta bulk mRNA-sequencing from n=124 first trimester (59 female, 65 male) and n=43 third trimester (18 female, 25 male) tissue samples. A subset of 23 pregnancies has matched placenta tissue collected at both first and third trimester. Tissue was collected at Cedars-Sinai Medical Center in Los Angeles, California, USA. First trimester placenta was collected at gestational ages of 70-100 days from leftover tissue from chorionic villus sampling for prenatal genetic diagnosis, after cleaning to remove maternal decidua. Third trimester placenta was collected after delivery at gestational ages 254-290 days from the fetal side near the umbilical cord insertion site beneath the amnion. Tissue was stored in RNAlater RNA Stabilization Solution (Invitrogen) at -80C until further processing. All pregnancies were conceived without fertility treatments, were normal karyotype, and resulted in live singleton births. Mothers with pre-existing diabetes or hypertension were excluded from the study, but not excluded if complications developed during pregnancy, though most pregnancies were uncomplicated. The average parental age was advanced (over 35 years old) but principal components analysis did not show clustering by either maternal or paternal age. RNA extraction was performed with physical homogenization of tissue followed by the AllPrep DNA/RNA/miRNA Universal Kit (QIAGEN), then 1 ug of the total RNA elution was used for library construction using the Illumina TruSeq Stranded mRNA library preparation kit (Illumina), with polyA mRNA selection then cDNA synthesis using SuperScript II reverse transcriptase (Invitrogen) and random primers. The cDNA was converted into double stranded DNA and PCR-amplified, then purified with Agencourt AMPure XP beads (Beckman Coulter). Sample libraries were multiplexed and sequenced on a NovaSeq 6000 platform (Illumina) using 75bp single-end mRNA-sequencing, with average 30 million reads per sample. Differential expression analysis was performed with DEseq2 to compare first versus third trimester placenta, adjusted for fetal sex [PubMed ID: 38271627]. Subanalyses were also performed to identify sex differences. Overall design: Human placenta was analyzed for differential gene expression across gestation (first versus third trimester, adjusted for fetal sex) using the DESeq2 R package. Subanalyses were also performed for first trimester placenta sex differences, third trimester placenta sex differences, female cohort first versus third trimester differences, and male cohort first versus third trimester differences.