Profiling the Small Non-coding RNA Transcriptome of the Human Placenta

Proper functioning of the placenta, the temporary organ crucial in fetal development during pregnancy, is critical for maternal and fetal health. While microRNAs (miRNAs) are known to impact placental gene expression, the effects of other small non-coding RNAs (sncRNAs) on the placental transcriptome are not well-established. Here, we performed small RNA sequencing of 30 chorionic villi samples of varying gestational ages (M = 23.5 ± 11.4 weeks). We observed expression of 1543 sncRNAs, including miRNAs, piRNAs, snRNAs, snoRNAs, and tRNAs, as well as 18,003 miRNA variants (isomiRs), and identified 48 previously-unannotated miRNAs. This novel characterization of the placental sncRNA transcriptome may aid future investigations of sncRNA regulatory functions within the human placenta. A total of 30 samples were obtained from first trimester, second trimester, and term pregnancies. First trimester samples were obtained after elective terminations. Second trimester samples were obtained after fetal demise conditions. Six of these second trimester samples were classified as having neural tube defects. After RNA extraction, samples were sequenced at Canada’s Michael Smith Genome Sciences Centre, in Vancouver.