Long non-coding RNAs in placental development and disease

To reconceptualize epitranscriptomics, long non-coding RNAs (lncRNAs) are emerging as future frontiers in the paradigm shift of stereotyped biological science. Long non-coding RNAs (lncRNA) represent a class of endogenous RNA molecules with length greater than 200 nucleotides but not exceeding 100 kilobases that do not encode proteins, yet transcribed by RNA Polymerase II and are poly-adenylated. Unlike protein-coding genes, they exhibit poor interspecies conservation. However, lack of sequence conservation does not imply the lack of function. Indeed, this dearth in evolutionary conservation challenges the functional investigation of lncRNAs. Previously characterized as products of pervasive transcription, recent advances in lncRNA research proposes them as imperative mediators of gene regulation at the transcription and post-transcriptional level. Ever-increasing amount of RNA sequencing data is expanding the lncRNA inventory to fundamentally dissect the architecture of eukaryotic complexity. Over the last two decades a flurry of studies identified quite a few placental lncRNAs. However, given the complexity of placental development, many questions have been raised regarding their biological function. Nonetheless, identification of lncRNAs of placental origin in the maternal circulation throughout pregnancy raised the prospect of lncRNAs being evaluated as prognostic biomarker of trophoblast associated disorders leading to adverse pregnancy outcome. In this review, we summarize key findings on the recent advances in lncRNA research during the development of the feto-maternal organ placenta and dys-regulations of lncRNA functionalities as prime determinants of placenta associated pregnancy complications.