Aberrant epigenetic regulation of placental function is implicated in several complications of pregnancy, such as preeclampsia, recurrent pregnancy loss and fetal growth restriction. Notably, the placenta has a unique epigenetic landscape, permissive for the activity of transposable element (TE) derived DNA sequences. TEs are often co-opted by the host genome as cis-regulatory elements, driving tissue- and species-specific gene expression programs. Indeed, TEs contribute many placental-specific enhancers in mouse trophoblast. However, the presence and role of a similar TE-derived regulatory network has not been explored in human trophoblast. As TEs are highly species-specific, such a network in humans would be expected to regulate species-specific placental characteristics, such as the deep interstitial invasion unique to great apes. TE-derived regulatory elements may therefore be important for placental homeostasis and be involved in diseases characterised by aberrant placental invasion. I propose to map TE-derived cis-regulatory sequences in human trophoblast ex vivo using their histone modification signatures. I will assess the regulatory potential of candidate TEs through transcriptomic analyses and motif analysis to reveal transcription factor binding sites, highlighting promising candidates of importance in the human placenta. I will then directly test the function of top TE candidates using CRISPR-Cas9 genome editing of the TEs in trophoblast in vitro, and measuring changes in expression of target genes. Finally, I will elucidate epigenetic and coding differences between complicated and normal control placentas at the functional regulatory TE loci I find, to identify correlations with disease. This project will provide a comprehensive analysis of an as-yet unexplored aspect of human placental epigenetic regulation, and potentially identify novel causes of common unexplained complications of human pregnancy.
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