Manifold roles of the chemokine G-protein-coupled receptor CCR7 in differentiation of human trophoblast into extravillous and syncytiotrophoblast lineages

The chemokine G-protein-coupled receptor CCR7 is expressed in extra-embryonic tissues of the early human embryo, including trophectoderm and its derivatives: cytotrophoblast, extravillous trophoblast (EVT) and syncytiotrophoblast (STB). However, its function in placentation remains understudied. Here, we have generated human embryonic stem cells harboring CCR7 deletions and differentiated them into human trophoblast stem cells (hTSC), their EVT and STB derivatives, and trophoblast organoids. We found that CCR7 mutant hTSCs exhibited delayed EVT differentiation: they retained hTSC-like characteristics, and exhibited decreased epithelial-to-mesenchymal transition and cell motility. Investigation of trophoblast organoids using single cell transcriptomics showed that CCR7 mutant organoids comprised a smaller EVT, but a larger STB population, compared to wild type. Whereas CCR7 deficiency increased cell fusion during STB differentiation, excess CCR7 reduced expression of fusion-associated genes. Mechanistically, we found that CCR7 limited early STB differentiation by reducing cAMP levels. Transcriptional profiling of CCR7 mutant STBs identified reduced gene expression related to the placental viral defense. Together, our studies demonstrate that CCR7 plays multiple roles in cellular decision-making during trophoblast differentiation, promoting EVT differentiation and limiting cell fusion during early STB formation.