The human placenta exhibits a unique transcriptomic void

Summary: The human placenta exhibits a unique genomic architecture with an unexpectedly high mutation burden and many uniquely expressed genes. The aim of this study is to identify transcripts that are uniquely absent or depleted in the placenta. Here, we show that 40 of 46 of the other organs have no selectively depleted transcripts and that, of the remaining six, the liver has the largest number, with 26. In contrast, the term placenta has 762 depleted transcripts. Gene Ontology analysis of this depleted set highlighted multiple pathways reflecting known unique elements of placental physiology. For example, transcripts associated with neuronal function are in the depleted set—as expected given the lack of placental innervation. However, this demonstrated overrepresentation of genes involved in mitochondrial function (p = 5.8 × 10−10), including PGC-1α, the master regulator of mitochondrial biogenesis, and genes involved in polyamine metabolism (p = 2.1 × 10−4).