Co-Expression Network Analyses Reveal Long Non-Coding RNA Programs Associated with Trophoblast Development and...

The human placenta plays a critical role as an immune and mechanical barrier. Notwithstanding, viral pathogens can still cross this barrier. Previously, differential gene expression has been described for protein-coding genes in human-induced-pluripotent-stem-cell-derived (hiPSC-derived) trophoblasts (TBs) from dizygotic twins discordant for congenital Zika syndrome (CZS), in which only one of the twin subjects presented the microcephaly phenotype. However, the involvement of long non-coding RNAs (lncRNAs) in TB development and in the TB response to ZIKV infection remained unexplored. To address this gap, we constructed a trophoblast-specific, lncRNA-enriched transcriptome resource and used it to define co-expression networks linking lncRNAs to trophoblast differentiation and to the antiviral response to ZIKV infection. Here, public RNA-Seq data from hiPSCs and hiPSC-derived TBs from dizygotic twins discordant for CZS were re-mapped to the human reference genome (GRCh38) using an ad hoc compiled hiPSC-TB-specific transcriptome enriched for lncRNAs, followed by differential expression analysis, co-expression network analysis and gene ontology (GO) enrichment. Expression validation by RT-qPCR of a set of novel and known lncRNAs associated with trophoblast differentiation and ZIKV infection was obtained. When comparing hiPSCs and TBs, 218 known and 26 novel lncRNAs were differentially expressed (DE) (FDR < 0.001). Correlated modules were enriched with GO terms related to "epithelial cell differentiation" and "tissue morphogenesis". Upon comparing TBs derived from the dizygotic twins, before and after ZIKV infection, 96 known and 6 novel lncRNAs were DE (FDR < 0.05). Correlated modules were enriched with interferon-related GO terms, including "regulation of defense response to virus" and "response to interferon". ZIKV-infected TBs from microcephaly-affected twins showed a 2.5-fold lower number of DE protein-coding genes and a 2-fold lower number of DE lncRNAs, compared with ZIKV-infected TBs from non-affected twins. These results indicate lncRNAs associated with TB development and response to ZIKV infection, highlighting candidates to be prioritized in future functional studies, such as CARINH, PSMB8-AS1, HCP5, BISPR and imprinted H19 and MEG3 lncRNAs.